Water-Supply and Irrigation Paper No. 185 Series L, Quality of Water, 15 

DEPARTMENT OF THE INTERIOR

UNITED STATES GEOLOGICAL SURVEY

CHARLES D. WALCOTT, DIRECTOR

INVESTIGATIONS

ON THE

PURIFICATION OF BOSTON SEWAGE

Made at the Sanitary Research Laboratory and Sewage Experiment Station 

of the Massachusetts Institute of Technology

WITH A

HISTORY OF THE SEWAGE-DISPOSAL PROBLEM

BY

C.-E. A. WINSLOW AND EARLE B. PHELPS

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1906

CONTENTS.

	Page, 

Introduction, by William T. Sedgwick.............. ...................... 5

History of the sewage-disposal problem..................................... 9

Nature of the problem................................................ 9

Composition of sewages............................................... 13

Disposal of sewages by dilution in lakes, rivers, and the sea............. 16

Disposal of sewages by broad irrigation or sewage farming .............. 24

Treatment of sewages by chemical precipitation........................ 29

Purification of sewages by intermittent nitration through sand.......... 35

Treatment of sewages in the septic tank ............................... 42

Purification of sewages by the contact process in beds of coarse material.. 53 

Purification of sewages by a continuous trickling process over coarse

material........................................................... 75

Recent tendencies in sewage-disposal practice in England, Germany, and

the United States..................... ............................... 88

Experiments on the purification of Boston sewage, 1903-1905................ 97

The sewage experiment station........................................ ' 97

Analytical methods and interpretation of results I....................... .107

Character of the crude sewage......................................... Ill

Removal of suspended matter......................................... 114

Preliminary treatment in the septic tank .....'................-........ 119

Purification by intermittent sand filtration............................. 126

Purification in contact beds of coarse material.......................... 132

Conclusions bearing on the treatment of Boston sewage................. 147

Acknowledgments.................................................... 149

Bibliography ............................................................ 149

Index ................................................................... 155

3
ILLUSTRATIONS.

Page. 

FIG. 1. 'Diagram illustrating self-purification of Sudbury River ............. 17

2. Diagram illustrating self-purification in the Thames, England....... 19

3. Seasonal variations in the condition of Merrimac River at Lawrence,

Mass.......................................................... 22

4. Seasonal variation in gas production in the septic tank.............. 44

5. Progressive effect of septic action at Lawrence, Mass................ 46

6. Loss in capacity of contact beds at Manchester, England............ 64

7. Comparison of sewages and efiiuents from contact beds ............. 68

8. Comparison of sewages and effluents from trickling beds............ 84

9. Map of Massachusetts metropolitan sewerage district ............... 97

10. Plan of Massachusetts Institute of Technology experiment station

grounds and buildings.......................................... 98

11. Detail of grit chamber............................................ 100

12. Plan of ground floor of filter house................................ 101

13. Plan'of second floor of filter house ................................ 102

14. Section of filter house ............................................ 104

15. Composition of the crude sewage of Boston ......................... 112

16. Composition of septic effluents........-......-..--....-.-....-,.-. 120

17. Comparison of various forms of nitrogen in crude sewage and sandfilter effluents.................................................. 130

18. Comparison of effluents from primary-contact beds of various-sized

stone..-....-._....--...._-...---...--_----.------.---.-------- 141

19. Comparison of effluents from primary-contact beds of different

depths ........................................................ .143

20. Comparison of effluents from primary-contact beds at different rates. 144

21. Comparison of effluents from double-contact systems taking crude

and septic sewage -.........-........-.....--..-....---.--....-- 146

22. Comparison of sewages and effluents from single and double contact

beds ...................................:.-...-.-..........-.-. 147
INVESTIGATIONS ON THE PURIFICATION OF 

BOSTON SEWAGE.

By C.-E. A. WINSLOW and EAKLE B. PHELPS.

INTRODUCTION.

By WILLIAM T. SEDGWICK.

Systems of water carriage, or sewerage, are now almost universally 

employed for the quick and inoffensive removal of fluid wastes and 

human excrements from thickly settled communities. These fulfill 

fairly well that first and most imperative requirement of scientific 

sanitation the prompt and efficient removal of the more dangerous 

excreta. As often happens, however, the solution of one problem has 

given rise to another scarcely less difficult, namely, in this case, the 

sanitary and economic disposal of vast quantities of contaminated 

liquids known as sewage. The volumes of sewage discharged by 

modern communities are so large, especially in the United States, 

where water is liberally supplied, freely used, and frequently wasted, 

and the character of all kinds of sewage is always so objectionable, 

that the so-called sewage-disposal problem becomes, from the economic 

as well as the sanitary point of view, one of the most serious with 

which modern communities have to deal. Nor is this merely a public 

or community problem. Isolated private houses of the better class 

are now almost invariably abundantly fed with running water a 

supply which has become one of the greatest necessities as well as one 

of the greatest luxuries of civilized life. In such houses the watercarriage system for the disposal of household wastes of all kinds has 

found favor no less than in crowded communities. Here, also, it 

entails a difficult problem, i. e., the ultimate disposal of large quantities of noxious sewage; and for the house no less than for the community it is important to secure this ultimate disposal in such a way 

as to avoid the creation of any insanitary focus or foci in the environment, or any infringement of the laws of hygiene and sanitation.

5
D THE PURIFICATION OF BOSTON SEWAGE.

Moved by the magnitude and gravity of the sewage-disposal problem as it concerns householders and communities, an anonymous 

friend of the Massachusetts Institute of Technology, in 1902, presented to that institution the sum of $5,000 a year for three years, for 

the purpose of making experiments on sewage purification and of giving the widest possible publicity to means or methods by which the 

present too often crude and imperfect systems may be improved. In 

a letter which constituted a virtual deed of gift, the donor designated 

a preference for the following lines of activity:

1. For keeping up with the investigations of the best workers in all countries.

2. For utilizing this knowledge in the work of the Massachusetts Institute of Technology.

3. For original experiments.

4. For distributing all over the country the results of the work in such words that he who 

runs may read.

5. For inciting students to make plain and simple statements of the results of their 

studies.

The gift thus made was gratefully accepted by the authorities of the 

Massachusetts Institute of Technology, and the planning and organization of the work to be done were assigned by them to the writer, 

head of the department of biology, who had for some years served as 

lecturer in the Institute on sanitary science and public health, and had 

also gained considerable experience in sewage purification during a 

connection of several years with the work of the State board of health 

of Massachusetts. In view of the limited means available and the 

long-continued and well-known investigations of the Massachusetts 

State board of health at the Lawrence experiment station, dealing 

chiefly with the sewage of an inland city; in view, also, of the increasing use of harbors for the disposal of the sewage of seaboard towns, 

with the growing dangers of contamination of shellfish, pollution of 

bathing beaches, and the like; and especially in view of the desirability of making the new work of practical educational value to the 

students of the Institute of Technology, who might carry away with 

them into active life and to all parts of the country the results of personal knowledge of the work, it was decided to establish a sanitary 

research laboratory and sewage experiment station on the main trunk 

sewer of the south metropolitan system of the great seaboard city of 

Boston. The precise point finally chosen, near the corner of Massachusetts avenue and Albany street, has proved very convenient and 

favorable. Here a piece of land formerly occupied by a livery stable 

was secured on a long lease, the stable itself was turned into a tank 

house, and a smaller building on the premises was fitted up as an 

office, with chemical and bacteriological laboratories connected. Open 

space enough remained for the construction later of outdoor filters 

and a large trickling filter. Permission was obtained for making 

connections with the main trunk sewer of the south metropolitan
INTRODUCTION. 7

system on its way to the sea at a point where it contained the sewage 

of a contributing population of about half a million people, and for 

drawing sewage from this sewer as needed. A pump was installed, 

tanks were constructed for tests of various methods of sewage purification, and a working organization was effected by the formal 

appointment of the writer as director, of C.-E. A. Winslow as biologist 

in charge of the laboratory and station, and of Earle B. Phelps, a 

graduate of the Institute in the department of chemistry, and for some 

years assistant at the Lawrence experiment station of the Massachusetts State board of health, as research chemist and bacteriologist. 

A full description of the laboratory and experiment station is given 

on pages 97-107, illustrated by figs. 10-14:

The elaborate and long-continued experiments of the State board 

of health of Massachusetts at the Lawrence experiment station on 

intermittent sand filtration as a me,ans of sewage purification made 

it advisable to set up only three filters of this kind, largely for demonstration purposes and for the benefit of students. To the so-called 

septic-tank method it was felt necessary to give somewhat more attention, the value of this process under various conditions being still 

somewhat problematical; and to the contact system much attention 

was given for the same reason. More recently, continuous filtration 

by means of trickling filters has come to the front, particularly in 

England, and this system of disposal has therefore required especially 

careful consideration and study.

As a prerequisite for all these investigations it was plainly necessary 

to make, in the first place, careful examinations of the character and 

amount of the sewage actually discharged by the south metropolitan 

system of Greater Boston. The results of these examinations have 

already been published, together with other papers, in vol. 1 of "Contributions from the Sanitary Research Laboratory and Sewage Experiment Station of the Massachusetts Institute .of Technology," of 

which the present work is volume 2. Volume 1 appeared originally 

in the "Journal of Infectious Diseases," volume 1, supplement No. 1, 

Chicago, 1905, and was also reprinted as a separate brochure. This 

latter was in large demand and is now unfortunately out of print, 

but a limited number of the copies of the "Journal of Infectious 

Diseases" containing these papers may still be purchased from 

the publishers. As a matter of record the titles of the papers may 

here be given, as follows:

The chemical and bacterial composition of the sewage discharged into Boston Harbor 

from the south metropolitan district. C.-E. A. Winslow and E. B. Phelps.

The number of bacteria in sewage and sewage effluents determined by plating upon different media and by a new method of direct microscopic enumeration. C.-E. A. Winslow.

The mode of action of the contact filter in sewage purification. E. B. Phelps and F. W. 

Farrell.
8 THE PUElFICATIOtf OF BOSTOtf SEWAGE.

A critical study of the methods in current use for the determination of free and albuminoid 

ammonia in sewage. E. B. Phelps.

The determination of the organic nitrogen in sewage by the Kjeldahl process. E. B. 

Phelps.

Test of a method for the direct microscopic enumeration of bacteria. C.-E. A. Winslow 

and G. E. Willcomb.

The present volume contains, first, a careful and elaborate historical 

review of the whole sewage-disposal problem from its origin in the 

wide adoption of the water-carriage system up to the present time, 

when that system has become practically universal. This interesting 

review can not fail to be of the highest value to expert engineers, sewage commissioners, and communities all over the United States, especially those numerous small communities which are confronted, perhaps for the first time, with a problem which means so much for the 

health as well as the finances of the citizens.

Following the historical review is a full description of the experiments thus far made on the sewage of a great American seaboard city, 

together with comparisons with similar work done elsewhere, with practical conclusions which have been drawn from the experiments and 

specific statements concerning the comparative merits of various systems of purification tested. These are by no means applicable merely 

to large cities or to seaboard cities, but contain lessons of practical 

value for all sorts of communities having to deal with the ever 

present sewage-disposal problem.

This report is by no means final, for experiments are still in progress 

not only along these lines but also along others more recently developed. In particular, the percolating, trickling, or continuous filter 

method is being more extensively tested, with results which it is hoped 

may be ready for publication by the end of another year.

The donor of the original gift has consented to continue the work 

for the fourth and fifth years an immense advantage in work of this 

kind, which grows in interest and value with the lapse of time as well 

as with the experience gained by the workers on the problems involved. 

In consonance with the wishes of the donor as expressed in the deed 

of gift, it is the intention of the director to prepare a brief popular 

statement of the facts contained in this volume, in language so simple that citizens, boards of health, and sewerage commissions may 

readily avail themselves of the information here contained, and so that, 

as desired by the donor, "he who runs may read."

The work here described and the results here recorded have no connection with the well-known work of the State board of health of 

Massachusetts and no official connection with the city of Boston or 

any of its departments. They proceed entirely from an educational 

institution the Massachusetts Institute of Technology and all the
HISTOKY OF SEWAGE-DISPOSAL PKOBLEM. 9

officers and workers at the laboratory and station have been either 

officers, graduates, or students of the Institute.

If, however, as is quite within the bounds of possibility, it should 

ever become necessary to purify the sewage of Greater Boston, or of 

any part of it, before discharging it into the waters of Boston Harbor, 

there is reason to believe that these studies may have a practical local 

value in proportion to their cost. Meantime, it is the wish of the 

director no less than of the donor that they may be found immediately serviceable to numerous American communities confronted with 

' the sewage-disposal problem and seeking means for its solution.

In addition to those persons already mentioned, the working staff 

of the laboratory and station has included, for longer or shorter periods, Prof. S. C. Prescott, of the Massachusetts Institute of Technology; 

Prof. E. G. Smith, of Beloit College; Miss Anne F. Rogers, and Messrs. 

George R. Spalding, Frederick W. Farrell, George C. Bunker, George 

E. Willcomb, James A. Newlands, William H. Beers, and William T. 

Carpenter, all of whom have contributed directly or indirectly to the 

discussions and results contained in this volume.

MASSACHUSETTS INSTITUTE OF TECHNOLOGY,

Boston, April, 1906.

HISTORY OF THE SEWAGE-DISPOSAL PROBLEM.

NATURE OF THE PROBLEM.

The disposal of waste is a fundamental problem for all living 

organisms. As the body takes in food and builds it up into its own 

peculiar structure, so it must continually break down and give off 

waste products, which, as a rule, if they accumulate, prove poisonous 

to the organism itself. This is the case with the individual; it is still 

more the case when large numbers of organisms are closely congregated together in communities. The political body resembles the 

organisms of which it is composed in no merely fanciful sense. It is 

subject to the laws of organic life; it has its income and its outgo; and 

a failure to remove the waste products of its life processes is inevitably 

dangerous to the units of which it is composed.

In spite of these facts, the attempt at scientific waste disposal is 

comparatively recent. The Cloaca Maxima and the other so-called 

sewers of antiquity were rather drains than sewers, and their function 

was to lower the ground-water level and not primarily to remove 

excretal wastes. Until 1815 the discharge of any waste but kitchen 

slops into the drains of London was prohibited by law, and the same 

regulation persisted in Paris up to 1880. Sewerage and sewage dis-
10 THE PURIFICATION OF BOSTON SEWAGE.

posal proper really date from the epoch-making report of the health 

of towns commission of Great Britain in 1844, a which revealed the 

accumulation of such an astonishing amount of decomposing organic 

matter and filth of all kinds in the cities that it aroused British sanitarians to a strong movement for the amelioration of these conditions 

and led to the development of the filth theory of disease the theory 

that disease is bred in heaps of decomposing filth. This pythogenic 

theory of Chadwick and Murchison we now know to be wrong in its 

essential assumption that infective material is created de novo by 

decaying organic matter; yet it was right in laying emphasis on filth 

as a carrier of disease. The wonderful administrative work of the 

British sanitarians, acting on this partially erroneous theory, effected 

the greatest sanitary progress which has probably ever been known. 

Public and private cleanliness was taught and practiced as never 

before. The midden system and the pail system rapidly gave way to 

the water-carriage system. Whereas in 1815 the sewers of London 

were simply drains to carry off the storm water the discharge of sewage into them being forbidden bylaw in 1847, only three years after 

the report of the health of towns commission, it was made obligatory 

to discharge all sewage into those drains.

In other countries the example set in England was more or less 

promptly followed. In the United States numerous drainage systems existed, one in Boston, for example, dating from the seventeenth 

century; but the first comprehensive sewerage project was designed

a Frequent reference will be made to the investigations of the royal commissions of Great Britain, 

and in order to Avoid confusion the following chronological summary of the work of those commissions 

which have dealt with sewage disposal and allied subjects is quoted from A. J. Martin:

1843. Royal commission appointed "to inquire into the present state of large towns and populous districts" (health of towns commission).

1844. First report of health of towns commission.

1845. Second and final report of health of towns commission.

1857. Royal commission appointed to inquire as to the best means of distributing the sewage of towns 

(sewage of towns commission).

1858. Preliminary report of sewage of towns commission.

1861. Second report of sewage of towns commission.

1865. Commission appointed to inquire in the best means of preventing the pollution of rivers (rivers

pollution commission). 

Third report of sewage of towns commission. 

1868. Second rivers pollution commission appointed.

1870. First and second reports of rivers pollution commission.

1871. Third report of rivers pollution commission.

1872. Fourth and fifth reports of rivers pollution commission. 

1874. Sixth-and final report of rivers pollution commission.

1882. Commission appointed to inquire into the effects of the discharge of the sewage of the metropolis 

into the river Thames (metropolitan sewage commission).

1884. First report of metropolitan sewage commission.

1885. Second and final report of metropolitan sewage commission.

1898. Commission appointed to inquire and report what methods of treating and disposing of sewage

may properly be adopted (royal sewage commission). 

1901-2. Interim report of royal sewage commission.

1902. Second report of royal sewage commission.

1903. Third report of royal sewage commission.

1904. Fourth report of royal sewage commission.
NATURE OF SEWAGE-DISPOSAL PROBLEM. " 11

by E. S. Chesbrough for the city of Chicago in 1855. On the continent 

of Europe a sewer system was constructed at Hamburg after the great 

fire of 1842, by Lindley, an English engineer. Berlin began her sewerage in 1860 and other German systems quickly followed. France and 

the Latin countries, though still somewhat inadequately sewered, are 

making progress. No law of sanitation is now more clearly recognized than the principle that the wastes of human life must be diluted 

with an adequate supply of water and quickly removed from the 

region of habitation.

With the establishment of the water-carriage system the difficulty 

was shifted from the individual to the community. The insanitary 

conditions surrounding the dwelling were relieved, "but at some point 

on the outskirts of the city the concentrated filth from its entire population must be disposed of. The vast volume of water in which the 

excretal elements are distributed makes the problem only more difficult. In England the average daily flow of sewage is about 25 gallons per capita. In London it is 34 gallons (R. S. C., 1902 b°). In 

the United States, on the other hand, the flow in several small Massachusetts cities is estimated at about 100 gallons (Fuller, 1903), while 

for the south metropolitan district of Boston it is over 250 gallons 

(Winslow and Phelps, 1905). In the latter case the yearly flow of 

sewage amounts to 46 billion gallons a fair-sized river. The organic 

matter to be treated includes during the year over 1,500,000 kilograms of nitrogen in the form of free ammonia alone. The treatment 

of such a volume of waste material offers a problem in applied chemistry of no mean magnitude.

The undesirable constituents in sewage may be considered under 

two heads living germs and dead organic matter. The first create 

disease; the second breeds nuisances. The germs of almost any disease of man or the lower animals may gain access to sewage, and, in 

the case of typhoid fever in particular, the infection may be transmitted through its agency so as to cause epidemics on a disastrous 

scale. The experiments of Jordan, Russell, and Zeit (1904) and of 

Frost (1904) indicate that typhoid bacilli in water, and particularly 

in sewage-polluted water, for the most part die in a few days. Yet 

the statistics of Lowell, Lawrence, Chicago, Philadelphia, Pittsburg, 

and Newark indicate that the typhoid germs which survive a sojourn in sewage and water are sufficiently numerous to produce 

serious results. Therefore where shellfish are taken from an estuary 

into which sewage is discharged it is desirable to subject the sewage

o Complete references to all literature cited in this report will be found in the bibliography at the end. 

References in the text include the name of the authority (the initials in the case of the British commissions) and the date of publication, with a distinguishing letter in case more than one volume appeared 

in a single year. This serves simply to identify the article or book, the full title of which is given in the 

bibliography.
12 THE PUEIFICATION OF BOSTON SEWAGE.

to some process such as sand filtration which effects a considerable 

reduction in bacterial content; and the sterilization of an effluent 

after its complete oxidation might, under certain conditions, prove 

desirable. As a rule, however, if the effluent from a sewage plant as 

discharged into a stream is clear and nonputrescible, the process is 

considered to be satisfactory. It is becoming more and more clearly 

recognized that all polluted waters, perhaps all surface waters, should, 

before they are used for drinking, be treated by water filters designed 

for the special purpose of removing disease germs. If such filtration 

as this is to follow, it is unnecessary to place on the sewage-purification works the extra burden of bacterial removal. The immediate 

and pressing need at the sewer outfall is the disposal of the organic 

matter, which threatens to create a nuisance by its decomposition. 

This organic matter may often be rendered harmless by means quite 

different from those calculated to effect high bacterial removal. 

When such is the case, it is scarcely fair to hamper the essential task 

of sewage disposal by demanding a bacterial purification which can 

be better attained by subsequent special treatment in water filters. 

All sewage-purification processes, as a matter of fact, materially 

reduce the number of bacteria present; but this must in general be 

regarded as incidental, the success of the process being gaged chiefly 

by the fate of the organic matter.

Where the waste from manufacturing processes is abundant, certain 

special problems are introduced. The material to be handled may 

be greatly increased in amount and the added material may be 

organic matter of a specially refractory kind, such as is found in woolscouring waste, tannery waste, and brewery waste. Furthermore, the 

presence of mineral poisons may interfere with the very processes 

which bring about the purification of the organic matter present. 

The acid-iron sewage of Worcester is an example of this sort, the biological processes of purification being appreciably hampered by the 

waste liquors from wire mills. The waste from the sulphite-pulp 

mills offers a notable example, carrying vast amounts of refractory 

organic matter, together with antiseptics which prevent any bacterial 

treatment until they are removed. Such industrial wastes require 

specific treatment in each case, generally along mechanical and chemical lines. They offer special problems quite distinct from the main 

question of sewage treatment, to which it is desired to limit the 

present paper.

In the disposal of ordinary domestic sewage it is primarily dead 

organic matter which must be dealt with. The products of the 

metabolism of men and animals and the partially decomposed waste 

materials from the preparation of food are largely made up of unstable 

organic compounds. They must be further decomposed, and the 

decomposition may follow either of two different courses. Under
COMPOSITION OF SEWAGES. 13

ordinary conditions a rapid reduction of any available oxygen first 

takes place, followed by an incomplete anaerobic putrefaction, accom-- 

panied by the evolution of methane, carbon dioxide, nitrogen, hydrogen, and various ill-smelling gases, such as hydrogen sulphide and 

the mercaptans. Such a process is- likely to create a nuisance objectionable from economic as well as esthetic grounds. The odors of 

decomposition may even become so objectionable as to menace the 

public health.

. The history of the organic matter is quite different if its decomposition takes place in the presence of an abundant supply of oxygen. 

If dry organic matter is burned, it is converted in to water and the 

oxides of carbon and nitrogen. If moist organic matter is allowed 

to ferment in the presence of an ample supply of oxygen, a slow oxidation is accomplished by the activity of certain micro-organisms, 

and the end products are again water, carbon dioxide, and nitrates. 

This aerobic fermentation is free from odor, and its end is the complete conversion of the decomposition products into harmless inorganic constituents. Such an oxidation alone can finally disposfe of 

the excretal products and prevent the obnoxious conditions attendant 011 anaerobic putrefaction. This is the rational aim of all processes of sewage disposal, which may be defined as methods for the 

conversion of the waste products of organic life and death into their 

oxidized and mineral forms.

COMPOSITION OF SEWAGES.

Chemically considered, sewage is a'dilute solution and suspension 

of certain organic and inorganic substances in water. The statement, originally made in 1890 by Hiram F. Mills and often' quoted 

by subsequent writers, that "a sewage stronger than ordinary would 

contain, say, 998 parts of pure water, 1 part of mineral matter, and 

1 part of animal and vegetable matter," serves its intended purpose 

in fixing an upper limit for the constituents of sewage, but is excessive 

for the sewage of American and English cities in its estimate of solids. 

From the data available it may be stated that 800 parts per million 

of total solids, as against 2,000 parts given by the standard mentioned, is a liberal figure for American cities and is exceeded by few; 

English cities may average about twice as much, while the continental European cities vary widely, but in few cases exceed 2,000 

parts.

Of the total solids in a sewage it may be said roughly that from 

60 to 70 per cent is in solution, either true or colloidal, the remainder 

being insoluble matter in suspension. Measured by the nature of 

the solids, about one-half, as a rule is volatile on ignition, representing in the main organic matter, while the remainder, called the fixed 

solids, represents the mineral matter originally present, as well as
14 THE PUEIFICATION OF BOSTON SEWAGE.

the mineral ash of the organic matter. The fact should be empha- 

 sized in this connection that many mineral substances are lost on 

ignition and that the combustion of nearly all organic substances 

occurring in nature leaves a greater or less amount of mineral ash. 

By far the larger part of the fixed solids is found dissolved, this 

amount on the average reaching about 75 per cent of the total, most 

of the remainder being sand or other insoluble matter, largely derived 

from street washings. The division of the organic matter is about 

equal between dissolved and suspended matter.

Concerning the character of the mineral matter present, it may be 

said that the portion in solution is of little consequence in relation 

to sewage treatment. It consists largely of sodium chloride. In 

certain special cases dissolved mineral matter may be precipitated 

during treatment and become burdensome. This is especially the 

case where iron salts are present in considerable amount. The 

insoluble mineral matter and the mineral residue from organic matter 

concern the present discussion more immediately, since in many 

processes of treatment these materials will accumulate to the detriment 

of filters. They normally amount to perhaps 10 per cent of the total 

solids and in the case of cities sewered on the separate system will 

not vary materially from that proportion. Combined sewers, however, admitting storm water from the streets, deliver an immense 

amount of sand and similar material during a storm, for the care of 

which some provision must be made at the disposal plant. No estimate can be made of the amount of such material likely to be delivered. It will depend entirely on local conditions, especially on the 

nature of the streets and the soil and on the severity of storms.

The character of the organic matter is of much greater importance. 

It is customary to speak of nitrogenous and carbonaceous matter, 

although the nitrogenous matter contains as a rule more carbon than 

nitrogen. Since, however, organic matter containing nitrogen gives 

rise on decomposition to products offensive to the senses, and since 

the various products of its oxidation are readily determined by simple analytical methods, much greater stress has always been laid on 

the nitrogen in sewage than on any other element. The total nitrogen value for American city sewages may be roughly placed at from

15 to 35 parts per million. Of this amount from one-third to onehalf, depending on the condition of the sewage, will be in the form of 

free or saline ammonia, largely as ammonium carbonate. The 

remainder, say from 10 to 25 parts per million, exists in combination 

as organic nitrogen. The nitrogenous organic material present in 

part results from the breaking down of proteid or albuminous material in digestion and in part represents unaltered proteid material. 

Albumin contains about 16 per cent of nitrogen, while its decomposition products leucine, tyrosine, and various other amido-acids 
COMPOSITION OF SEWAGES. 15

contain from 8 to 10 per cent, so that 10 per cent may perhaps be 

taken as an average value for the ritrogen in the nitrogenous material. This gives an amount of such material equal to from 100 to 

250 parts per million in the sewages under discussion. Roughly, 

about one-half of this nitrogenous material is carbon in organic combination, giving from 50 to 125 parts per million of carbon. The 

total carbon of such sewages may be expected to be between 100 and 

300 parts, say 200 for an average, of which perhaps 75 parts are 

found in the nitrogenous material. This leaves 125 parts of carbon 

as carbonaceous (nonnitrogenous) material, of which the greater 

part is cellulose or some other carbohydrate and fat. From the 

rather meager data available as to the amount of fat in sewage, it 

may be concluded that 50 parts per million is perhaps a fair average 

figure. Seventy per cent of the fat, or 35 parts, is carbon, which, 

deducted from the 125 parts previously mentioned, leaves about 90 

parts of carbon as carbohydrate. The proportion of carbon in carbohydrates being taken at 46 per cent, this gives 200 parts per million of carbohydrate. The figures thus deduced may be taken as 

fair average figures for American sewages. Considerable variation 

from the estimates may be found, amounting to perhaps 50 per cent 

on either side, but the relative amounts seem to be fairly constant 

as far as can be judged from available data. For the sake of clearness these typical figures are tabulated below:

Composition of an ideal sewage. 

[Parts per million.a]

H, O, S, P, etc .............................................

H, 0... ................................................

Total H, O, S. P, etc ..........................................

Total.

800

400

400

150

15

75

60

250

50

35

15

200

90

110

200

15

185

In solution.

500

300

200

In suspension.

300

' 100

200

oAll analytical results in this report are expressed in parts per million, 

authorities have been converted to the same basis.

Data cited from other

In order to change these figures to grams per capita per day it is 

only necessary to multiply by 0.38, a daily flow of 100 gallons per 

capita being assumed.

The sewage of English cities is in general stronger than the figures 

given here for a typical American sewage. Analyses previously compiled (Winslow and Phelps, 1905) indicate that the total solids in
16 THE PUBIFICATION OF BOSTON SEWAGE.

European sewages will average about 1,500 parts per million, with 

a range of from 500 to 2,100 parts. The organic constituents also, 

as measured by total organic nitrogen, indicate that European sewages are twice as strong as American. Values for oxygen consumed 

are not comparable on account of differences in analytical methods, 

but those for free ammonia are much more nearly equal in the two 

cases.

The amount of oxygen required to convert these organic substances into the mineral form is considerable. Dibdin, as shown in 

Table I, estimates it at from one to three times the weight of the 

organic substance-to be acted on.

TABLE I. Parts of oxygen required to oxidize one part of mrious organic substances

(Dibdin, 1903}.

Substance.

Oxygen required.

By the nitrogen.

0.523 

.411 

.457

By the hydrogen.

0.528 

.568 

.568 

.496 

.496 

1.016

By the 

carbon.

1.333 

1.310 

1.414 

1.184 

1.184 

2.025

Total.

2.384 

2.289 

2.439 

1.680 

1.680 

3.041

Oxygen 

already 

present.

0.251 

.294 

.220 

.494 

.494 

.113

Difference, 

or additional oxygen required for 

complete 

oxidation.

2.133 

1.995 

2.219 

1. 186 

1.186 

2.928

The problem of sewage disposal is to supply this required oxygen 

and to supply it under such conditions that it will unite with the 

organic matter to be eliminated.

DISPOSAL OF SEWAGES BY DILUTION IN LAKES, RIVERS, AND THE SEA.

The most obvious way to dispose of sewage is to empty it into 

the nearest body of water. Before true sewers existed the natural 

drains discharged into the nearest watercourse, and when the drains 

became filled with polluting matter the same plan was followed. 

Within certain limits the process proved a success. When the volume of sewage was not too great it disappeared by dilution and was 

finally removed by the agencies involved in the " self -purification of 

streams." The dilution is, of course, only an aid to purification 

and not in itself an active agent in the process. A drop of ink in 

a barrel of water is still existent, though invisible. Sedimentation, 

too, is scarcely in itself a process of purification, although it performs a most important part, separating the solids and storing them 

so that other agencies may have time to act. Oxidation of the 

organic matter is the real purification process, and it is by virtue of 

this process that streams are able to dispose of organic pollution 

when they do so successfully.

The oxidation of organic matter in a stream or pond may be
SEWAGE DISPOSAL BY DILUTION. 17

partly due to direct chemical action. In the main, however, it is 

carried out by the activity of micro-organisms. The larger microscopic forms, the Crustacea, the rotifera, and the protozoa, play a 

part the exact importance of which is hard to estimate, especially 

in the consumption of the solid particles. The algae and other green 

plants exercise an important influence, as shown by Bokorny (1897) 

and others. The chief agents, however, are the bacteria, particularly those metatrophic and prototrophic forms which liquefy proteids, liberate free ammonia from more complex compounds, and 

oxidize it to the mineral form.

The process of self-purification of streams, though a real process, 

is a slow one. The rivers pollution commission of Great Britain concluded in 1874 that sewage mixed with twenty tinies its volume of 

pure water would be two-thirds purified in flowing 168 miles at a 

rate of 1 mile an hour. Long, in 1889, made a careful study of 

this process in the Illinois and Michigan Canal. A large part of 

the sewage of Chicago, diluted with the water of Lake Michigan, 

at that time flowed through the canal for a distance of 29 miles at 

a rate of about 1 mile an hour. Analyses from Bridgeport and Lockport, at the beginning and ,end of the canal, as shown in Table II, 

gave a purification of -23 per cent as measured by albuminoid ammonia and 27 per cent measured by oxygen consumed, with a removal 

of 46 per cent of the matter in suspension.

DISSOLVED OXYG&

MILES BELOW SAXONWLLE

FIG. 1. Diagram illustrating self-purification of Sudbury River.

TABLE II. Analyses of water from, the Illinois and Michigan Canal at Bridgeport and 

Lockport (Rafter and Baker, 1894}.

[Parts per million.a]

Place collected. Total 

solids.

471.2 

431.2

Matter in suspension.

129.2 

69.8

Nitrogen 

as 

nitrates.

0 

0

Chlorine.

4R.8 

46.1

Hardness 

(CaCO3).

201.3 

207.7

Nitrogen asFree ammonia.

10.1 

8.9

Albuminoid ammonia.

2.1 

1.6

Oxygen 

consumed.

22.1 

16.2

» Free and albuminoid ammonia values throughout this paper arc expressed as nitrogen. The method 

by which oxygen-consumed determinations were made is stated whenever it eould be ascertained from 

the original reports.

IKR 18E
18 THE PUBIFICATTOlSr OF BOSTON" SEWAGE.

Streams with more sluggish flow will naturally exhibit a greater 

purification in a short distance, since sedimentation will be greater and 

since the time during which the nitrifying organisms act is one of the 

chief factors involved. Sudbury River in Massachusetts, for example, 

is heavily polluted at Saxonville by the wastes from a woolen mill. 

It flows rapidly for about 3 miles below the mill and then enters an 

area of meadows where it winds along through a weedy channel at a 

rate not more than one-fourth mile an hour. In an investigation 

by Woodman, Winslow, and Hansen (1902) it was found that 3 miles 

below the entrance to the meadows and 6 miles below the mill the 

chemical constituents of the stream had fallen to their normal. The 

relations of albuminoid ammonia and dissolved oxygen on one of the 

days studied is indicated in fig. 1, in order to illustrate the progress of 

the purifying process. It will be noticed that below the point marked 

"Point of pollution" the albuminoid ammonia is greatly increased, 

and the dissolved oxygen, being absorbed by the organic matter, is 

correspondingly diminished. Gradually, however, normal conditions reassert themselves, more oxygen is absorbed, and the albuminoid 

compounds settle out and are oxidized. At the station 6 miles below 

the point of pollution both constituents have been restored to their 

original value. Throughout, the reciprocal variation of the oxygen 

and the oxidizable nitrogen are striking.

Next to the time element the amount of available dissolved oxygen 

is, as this diagram suggests, the chief condition for the purification 

process; and the whole history of the pollution and self-purification of 

streams may be traced by the diminution and gradual restoration of 

this constituent. Dibdin's studies of the Thames below London are 

most significant in this respect and illustrate on a practical scale the 

enormous volumes of the oxidizing agent needed. He estimates 

(Dibdin, 1904) that 2,000 tons of oxygen'are absorbed by the river 

between Teddington and Southend in this process. The proportion 

of dissolved oxygen, expressed as "Per cent of saturation," at various 

points along the river on the high tide is plotted in fig. 2 from figures 

given by Dibdin (1904) for 1893-94. As the river enters the city 

between Kew and Battersea its oxygen content falls from 70 per 

cent to 43 per cent, and the progressive pollution continues until at 

Woolwich the oxygen value is only one-fifth that of saturation. 

Below Barking Creek the heavy pollution ceases, absorption of oxygen overbalances its consumption, and the normal conditions are 

gradually restored. The same general relations are shown in Table 

III, quoted by the Connecticut State sewage commission (1899). The 

ratio of oxygen to nitrogen, which changes from 1:2 at Kingston, 

above London, to 1:62 at Greenwich, is most significant.
SEWAGE DISPOSAL BY DILUTION. 19

TABLE III. Dissolved gases in the Thames above and below London, England (Connecticut, 

1899). Analyses by Roscoe and Schorlemmer.

[Cubic centimeters per liter.]

Ratio of oxygen to nitrogen .....

Kingston.

52.7

30.3

7.4

15

1:2

Hammersmith.

4.1

15.1

1:3.7

Somerset 

House.

62.9

45.2

1.5

16.2

1:10.8

Greenwich.

71.25

55.6

.25

15.4

1:62

Woolwich.

63.05

48.30

.25

14.5

1:58

Erith.

74.3

57.0

1.8

15.5

1:8.6

When .in any river the proportion of organic matter is slightly 

increased over that in the Thames at Woolwich, the small proportion 

of dissolved oxygen may be quite consumed. Conditions change and

Per cent of

saturation

100

75

DISSOLVED 

OXYGEN

= 8~J

Scale ofmiles

FIG. 2. Diagram illustrating self-purification in the Thames, England.

instead of aerobic nitrification, anaerobic putrefaction is set up. 

Foul-smelling gases are produced, and in place of a self-purifying 

stream a septic tank or open cesspool is produced.

There is evidently a critical point in the purification of sewage by 

discharge into water. Up to a certain point the organic matter is
20 THE PURIFICATION OF BOSTON SEWAGE.

successfully nitrified. As soon, however, as the material to be oxidized exceeds the available oxygen, aerobic purification stops and 

putrefaction takes its place. Kideal has attempted to express the 

relation between the various factors involved in the form of an equation, XO=C (M N) S, where X = flow of a stream, O = parts of dissolved oxygen in the water of the stream per unit flow; S = volume of 

sewage or effluent; M = parts of oxygen consumed by a unit volume 

of sewage; N = parts of available oxygen in the form of nitrites and 

nitrates, and C a constant. When the available oxygen exceeds 

the demand all goes well; when it does not, trouble ensues.

The ocean furnishes seaboard cities with the most favorable possible conditions for disposal in water. At New York and many other 

places small sewers discharge at frequent intervals into tide water. 

In Boston this method caused a serious nuisance, and as a result a 

somewhat more elaborate system was begun in 1876. Since 1895 

two main sewers have discharged into the harbor, serving the city 

and surrounding metropolitan district, which includes 25 cities and 

towns with a territory of nearly 200 square miles. The sewage of the 

region north of the Charles flows continuously from an outlet near 

Deer Island Light and amounts to about 50 million gallons per day. 

The sewage from the region south of the Charles, averaging in 1904 

100 million gallons per day, has been discharged since 1884 at Moon 

Island, nearer the center of the harbor. Here, in order to protect the 

adjacent shores, it has been thought necessary to hold the sewage in 

four masonry basins and to discharge it only on the outgoing tide. 

September 19, 1904, a third outlet was opened to take the sewage 

from certain high-level regions in the south metropolitan district. 

This discharges continuously in the outer harbor near Nut Island and 

delivers 20 million gallons per day, leaving the diminished flow at 

Moon Island about 80 million gallons. Experience has shown that 

no serious nuisance is caused by the Deer Island and Moon Island 

outlets. The sewage in the first case disappears within 1J miles of the 

outlet, while off Moon Island the sewage stream may be traced outward round the south end of Long Island for perhaps 2 miles. In 

both cases passing boats find the immediate vicinity of the outlet 

unpleasant, and near Moon Island the value of property on the mainland is said to be affected. No serious menace to health, however, is 

involved. The sewage apparently produces no permanent damage in 

the harbor, and recent investigations carried out by J. H. McManus 

and A. W. Walker in the laboratories of the Massachusetts Institute 

of Technology indicate that even in high winds there is no tendency 

for sewage bacteria to be carried into the air and blown shoreward. 

So popular is the method of disposal in the sea that according to a 

review made by the Massachusetts State board of health in 1902
SEWAGE DISPOSAL BY DILUTION. 21

(Massachusetts, 1903) nearly one-half the population of that State is 

tributary to such systems. In general they have proved successful, 

although a serious nuisance is created in some places, as at Lynn, 

where the sewage is discharged in shallow water and over tidal flats. 

In any case it is certain that such methods of disposal will prove less 

and less satisfactory from year to year as the volume of sewage and 

the concentration of shore population increase. The presence of 

shellfish beds in locations affected by the discharge of sewage into 

tide water is a special problem of a serious nature in some localities. 

It has been exhaustively treated "by Fuller (1905 b). The royal sewage commission, in an extensive report on the shellfish question in 

1904 (R. S. C., 1904 c), concluded that this evil is a grave one, but 

that it must be met less by restricting sewage disposal than by regulating the taking and storing of shellfish.

The discharge of sewage into inland waters is less likely to be successful than disposal in the sea. The gravest dangers with large 

lakes and rivers have arisen from their simultaneous use for sewage 

disposal and water supply, as in the case of Chicago before the opening 

of the drainage canal, and to some extent since. In such a case the 

water supply should always be subjected to its own process of purification; yet where water for drinking is to be taken below the sewage 

outlet some treatment of the sewage before it discharges furnishes an 

additional safeguard that is eminently desirable. With smaller 

bodies of water the increasing proportions of sewage sooner or later 

exceed the purifying capacity of the stream or pond, and once this 

point is passed conditions rapidly become intolerable. Just such a 

condition existed in the Thames, England, prior to the treatment of 

the sewage of London by chemical precipitation in 1890. In a night 

trip down the river during one of the investigations of the metropolitan sewage commission of 1882 three of the five members of the 

commission and their clerk were nauseated by the odor. Gross nuisances of this sort have been created in many streams, both in this 

country and in England. Blackstone and Neponset rivers, in Massachusetts; Naugatuck River, in Connecticut, below Waterbury; Passaic 

River between Paterson and Newark, in New Jersey, and Chicago 

River before the opening of the drainage canal are notorious examples.

By the examination of various rivers it has been possible to fix 

fairly well the practical limits within which a stream can purify sewage 

with success. Stearns (1890) estimated that a stream flow of 7 second-feet could safely carry the sewage of 1,000 persons, while if the 

flow were reduced to 2.5 second-feet a nuisance would result. Hering 

(1888) set the lower limit at 2.5 to 3.3 second-feet. Goodnough 

(1903), after a careful study of various Massachusetts streams in 

connection with the proposed Charles River dam, placed the certain
22 THE PUBLICATION OP BOSTON SEWAGE.

danger line at 3.5 second-feet per 1,000 persons and found that with 6 

second-feet trouble rarely follows. .Johnson (1905) converted these 

figures into dilution volumes as follows:

TABLE IV. Proportions of sewage which can be discharged into a stream with safety (Johnson, 1905).

Authority. Nuisance 

probable.

Iinl6

Iin23

Nuisance improbable.

Iin45

Iin36

Roughly, then, it may be said that a stream will purify one-fiftieth 

of its volume of sewage, but not much more. In summer, when the 

volume of diluting flow is least, the high temperature accelerates bacDegrees

-t r

' TMPEKA 7 URE OF W. «TER

S

*>$

40 |

JAN. FEB. MAR. APR- MAY JUNE JULY AUG. SEPT OCT NOV. DEC JAN FEB. MAR APR MAY JUNE JULY AU3. SEPT OCT NOV. DEC.

FIG. 3. Seasonal variations in the condition of Merrimac River at Lawrence, Mass.

terial action and makes an abundant supply of oxygen specially necessary. Table V shows for Merrimac River, above Lawrence, the 

monthly ratios of stream flow to the sewage-contributing population, 

estimated at 185,000, together .with the mean monthly temperatures 

and the dissolved oxygen in the river water. The data are graphically 

shown in fig. 3 and bring out clearly the much greater demand on the 

purifying power of the river during the summer months. The curve 

for November and December, 1899, is worthy of special notice, since 

with no increase in dilution a fall in temperature, with its consequent 

slackening of fermentation processes, shows a marked rise in dissolved 

oxygen. Although at the lowest points the dilution does not fall 

below Goodnough's minimum of 6 second-feet and although the dissolved oxygen averages do not show complete exhaustion, the liver
SEWAGE DISPOSAL BY DILUTION. 23

is. sometimes distinctly offensive during the summer. Theoretically, 

while any dissolved oxygen remains there should not be putrefaction; 

practically, any value below 50 per cent of saturation is likely to be 

accompanied at times by malodorous conditions.

The data in the following table are taken from annual reports of the 

Massachusetts State board of health (Massachusetts, 1900 and 1901) 

and from Water-Supply and Irrigation Papers Nos. 35 and 47 of the 

United States Geological Survey (1900 and 1901):

TABLE V. Seasonal conditions in Merrimac River at Lawrence, Mass.

Month.

April.....................

July... ...................

September. . ..............

Flow per 

1,000 persons 

discharging 

sewage (second-feet) .

42.6

26.4

64.5

143.2

51.6

13.4

11.3

10.8

9.7

15.1

15.1

34.5

1899.

Temperature(°F.).

34

34

34

58

73

76

74

67

58

40

36

53

Dissolved 

oxygen 

(per cent 

of saturation).

96.3

88.1

95.6

99.3

84.4

71.1

66.6

58.3

57.2

53.7

78.1

84.3

77.8

Flow per 

1,000 persons 

discharging 

sewage (second-feet) .

18.2

89.1

87.7

100

54.1

21.4

9.8

10.1

8.2

13.6

31.6

36.6

39.9

1900.

Temperature(°F.).

33

34

35

41

54

73

77

75

71

62

46

38

63

Dissolved 

oxygen 

(per cent 

of saturation).

81.6

87.8

99.1

62.1

59.4

43.6

32.5

47.6

91.2

98

70.3

It is evident that for inland cities, except those situated on the 

largest lakes and rivers, some other process of sewage disposal must 

be substituted for the direct discharge into water. In England this 

is an old story. The first of the royal commissions on sewage disposal 

investigated the subject in 1857 and reported in 1865 that the only 

way to prevent the pollution of rivers was to purify town sewage by 

disposal on land. A second royal commission on rivers pollution, 

appointed in 1865, made five exhaustive reports between that date 

and 1874, and a third commission, on the metropolitan district, 

reported in 1884 that treatment of London sewage was essential to the 

protection of the Thames. In the United States the Massachusetts 

legislature in 1872 directed the State board of health to investigate 

and report 011 "the disposition of the sewage of towns and cities," 

eliciting a memorable series of reports from William Bipley Nichols 

and his associates, and in 1886 the Lawrence experiment station was 

founded for the study of sewage-disposal problems. To-day 23 cities 

in the State of Massachusetts alone maintain purification works. 

According to Fuller (1905), about 28,000,000 persons in the United 

States are connected with sewerage systems. The sewage from 

20,400,000 is discharged into fresh water and from 6,500,000 into the 

sea, leaving 1,100,000 connected with sewage-purification works.
24 THE PURIFICATION OF BOSTON SEWAGE.

DISPOSAL OF SEWAGES BY BROAD IRRIGATION OR SEWAGE FARMING.

The most obvious alternative to the discharge of sewage into water 

is its distribution over the surface of suitable land, allowing the 

liquid to pass through to join the great reservoirs of ground water 

below. When the amount of sewage on a given area is not excessive 

the organic solids do not accumulate, but are gradually decomposed 

with the formation of soluble products beneficial to the growth of 

the higher plants. The disposal of waste water in every dooryard 

early gave an illustration of this process, and the absorption of manure 

in the fertilization of land indicated the great power of the purifying 

agents involved.

The practice of sewage disposal by broad irrigation gained a firm 

empirical basis long before there was any comprehension of the true 

principles involved. At Bimzlau, Prussia, for example, in the sixteenth century, the water from a famous spring was delivered to the 

inhabitants and a primitive sewer installed. The sewage from the 

outfall was distributed for irrigation on privately owned farms as 

early as 1559 with marked success (Du Mares, 1883). At the Craigentinny meadows part of the sewage of Edinburgh has been treated 

by irrigation for over two hundred years. The development of this 

method in England was largely due to the health of towns commission of 1844 and the sewage of towns commission of 1857. The latter 

commission in 1858 gave a full description of the system at Milan, 

where the liquid refuse of the city was conducted by a canal called 

the "Vettabbia" to an irrigation area of about 4,000 acres. The 

same commission concluded in 1865 that "the right way to dispose 

of town sewage is to apply it continuously to land, and it is only by 

such application that the pollution of rivers can be avoided."

With the desire to dispose of polluting material grew up a still 

greater interest in sewage farming as a profitable method of turning 

organic wastes into valuable crops, Liebig and his followers having 

laid great stress on the danger of an exhaustion in the nitrogen supply. The two conceptions are well combined in the definition of 

irrigation by the British metropolitan sewage commission of 1884 as 

"the distribution of sewage over a large surface of .ordinary agricultural land, having in view a maximum growth of vegetation (consistent with due purification) for the amount of sewage applied."

Progress along these lines was rapid in England during the sixties, 

and many of the present sewage farms were then laid out, as Croydon 

(1861) and Aldershot (1864). On the continent of Europe the first 

irrigation plant to be successfully operated on a large scale was at 

Danzig. In 1869 a contract was signed with an English engineer, 

Alexander Aird, by which the sewage of the city and 1,300 acres of 

land were ceded to him for a term of thirty-two jrears, the entire
SEWAGE DISPOSAL BY BROAD IRR1GAT1OH. 25

maintenance of the sewerage system.being in his charge. The operation of this plant had a special interest on account of the severe 

winter weather to which it was subjected. At about the same time 

the application of sewage to land was begun at Paris by Mille and 

Durand-Claye, after much preliminary investigation by Schloesing, 

Muntz, and others, of the chemical and biological principles involved. 

At present a total area of 13,338 acres at Gennevilliers, Acheres, 

and two other adjacent places is irrigated with Paris sewage. The 

flow amounts to 185 million gallons a day. and the standard rate of 

filtration is 0.012 million (12,000) gallons per acre per day. a The 

sewage, after passage through screen chambers and detritus tanks, 

is distributed on farms which are mostly owned by private individuals, although the city operates a small area. Part of the land is 

used for pasturage and part for raising peas, artichokes, tomatoes, 

and other table vegetables. The sewage farms of Berlin do not date 

quite so far back. Operations were first begun at Osdorf in 1876, 

after a long investigation under the leadership of Rudolf Virchow. 

An area at Falkenberg was added in 1879, and two areas at Grossbeeren and Malchow were added in 1882. The farms are to-day the 

largest in the world, the sewage of a population of 1,750,000 being 

treated on 22,881 acres of land at a rate of 0.003 million gallons per 

acre per day. The crops are chiefly timothy and Italian rye grass. 

The farms are operated mainly by convict labor under German military disciplirse (Roechling, 1892).

The English sewage farms are so designed that the sewage is allowed 

to run continuously over the surface of the soil in as thin a film as 

possible without being specially encouraged to pass downward. As 

a rule, the sewage is brought to the highest level on the farm and 

thence distributed by open carriers following the contours; these in 

turn discharge through lateral carriers or ditches. On many farms 

special areas of porous soil are leveled so that they may be completely 

flooded, serving for intermittent filtration, which is discussed on 

pages 35-42.

To obtain an available area of proper soil is the chief problem in 

sewage farming. A light .soil on a sandy or gravelly subsoil proves 

most satisfactory, while peat, chalk, and clay are bad. All three are 

too impervious, and the last two are likely to discharge unpurified 

sewage through cracks and fissures. With unsuitable soils rates of 

filtration must be low. Rideal (1901) estimates that the sewage from 

100 persons can be treated on an acre of loamy gravel and that the 

number may rise to 500 under rarely favorable circumstances, while 

with stiff clay it falls to 25. The rates commonly in use in England 

vary from 0.002 million gallons per acre per day at Leamington and

a Throughout this report rates of filtration are expressed in millions of United States gallons per 

acre per day, and where possible in "net rates," i. e., total quantity passed in a given period divided 

by the number of days in that period.
26 THE PURIFICATION OF BOSTON SEWAGE.

Wrexham to 0.015 at Cheltenham and Birmingham (Watson, 1903). 

German figures range from 0.002 at Brunswick to 0.007 at Danzig, 

and probably average about 0.004 (Bredtschneider andThumm, 1904).

When an irrigation farm is overdosed it becomes "sewage sick," to 

use an expressive English term. The surface clogs, pools are formed, 

putrefaction begins; only a complete rest restores the health of the 

area. Under such conditions the temptation to discharge unpurified 

sewage into the nearest stream is very strong. At times of rain, when 

sewage flow is highest, the crops are least in need of water and may be 

seriously damaged by it. The aims of sewage purification are too apt 

under such conditions to be sacrificed to those of agriculture. Thus, 

at the famous Craigentinny meadows, where profitable crops are obtained from once barren areas of blown sands, we are told that "the 

great bulk of the foul water merely runs over the surface of the 

ground and deposits a portion of its suspended matter" (Barwise, 

1904). Many of the English farms, on the other hand, have been 

operated for thirty years with no nuisance and without the accumulation of offensive sludge.

The statistics for eight of the principal English farms have been 

compiled from the fourth report of the royal sewage commission (R. S. 

C., 1904 a, b) to form Table VI, and they give a fair idea of general 

practice. The low rates on clayey soil at Leicester, Rugby, and 

South Norwood will be noticed, as well as the fact that careful screening and settling has in most cases been found a necessary preliminary. 

The analyses, which from their source may be considered representative, indicate that English irrigation effluents are by no means of exceptional quality, although the Nottingham and Cambridge results 

are excellent. The Aldershot plant appears to be doing fairly well, 

considering the very strong sewage with which it deals, but at Altrincham and other places the purification is much less satisfactory. 

By incubator tests the Nottingham and Cambridge effluents stood 

very high, and of the samples from Leicester and Aldershot 90 per 

cent gave no secondary putrefaction. Norwood, Croydon, and 

Rugby, on the other hand, gave putrescible effluents about onefourth of the time. On the whole, it seems fair to conclude from a 

general survey of English conditions that when a sufficient area of 

porous soil with a low water table is available a well-managed irrigation area may prove a satisfactory method of sewage disposal from 

the sanitary standpoint.
TABLE VI. Statistics of sewage farms in England (R. 8. C., 

Farm.

Aldershot camp. .

Altrincham

(Cheshire).

TJeddington 

(Croydoni.

Nottingham, ....

South Norwood .

Date ofconstruction.

1864

1870 

1801

1895 

1891 

1880 

1807 

1864

Average dailyflow 

(million gallons).

1

.8 

4

7.25

.3

.6

Area offilter beds

(acres) .

120.5

35 

420

74 

1,350 

051 

35 

152

Rate (million gal- i

Ions per acre 

day).

0.008

.023 

.01

.3

.005 

.011 

. Od9 

.OD4

Character of soil 

and subsoil.

Sand............

Peaty soil lying 

upon sand and 

gravel.

Gravelly loam 

overlying 

gravel and 

sand.

Sandy loam 

overlying 

gravel and 

sand.

Stift clayey so.l 

overlying 

dense clay.

Light sandy 

10am and 

gravel overlying gravel 

and sand. 

Heavy loam 

overlying stiff 

clay.

Clay soil resting 

on London 

clay.

Character of 

sewage.

Purely domestic.

Domestic.....

Almost purely 

domestic.

Mainly d o - 

mestic; some 

orewery refuse.

Three-fourths 

domes tic; 

one - fourth 

trade refuse.

Four-sevenths 

domestic; 

three - sevenths trade 

refuse. 

Mainly domestic.

Purely domestic.

Method of treatment.

Screening, settling 

tanks, and land 

filtration.

Settling tank and 

land filtration.

Screening, surface 

irrigation, and 

filtration.

Screening, s e t - 

tling tank, and 

land filtration.

Screening, s e t - 

tling tanks, surface irrigation 

and flit ration 

combined. 

Screening, (p a r - 

tiall and land 

filtration.

Screening, settling tanks, 

surface irrigation and filtration combined. 

Screen ing, s e t - 

tling tanks, and 

surface irrigation (with a little filtration).

Analy

Material.

fSewage . . .

fSewage . . .

(

Sewage . . . 

[Effluent . .

fSewage . . . 

[Effluent . .

Sewage . . . 

Effluent . .

Sewage . . .

[Effluent . . 

Sewage. . .

Effluent. .

Sewage. . . 

Effluent . .

 i

a 

II

£ 

H

30

72

34

26

34

51

47

21
28 THE PURIFICATION OP BOSTON SEWAGE.

The economic advantage of sewage farming is somewhat more 

doubtful. English chemists estimate the manurial value of sewage at 

from 1 to 4 cents a ton (Rafter and Baker, 1894). This value can no 

doubt in part be recovered, since the crops grown on sewage fields are 

often astonishingly heavy. Whether it really pays to recover it 

depends on local economic conditions. In many English towns the 

operation of farms has proved unprofitable, and there is some tendency 

toward their abandonment. Lieut. Col. A. S. Jones and others are, 

however, ardent advocates of the process; and in certain cases the 

farm, besides paying all running expenses, yields in some years as 

much as $12 an acre toward rent (Baker, 1904). McGowan, Houston, 

and Kershaw, in their valuable report to the royal sewage commission, conclude:

Although we are of opinion that sewage farms in general can never be expected to show 

a profit if interest on capital expenditure is included, the fact that in favorable seasons 

some of them more than cover the working expenses is a point in favor of cropping in connection with the land treatment of sewage. [R. S. C., 1904 c.]

With regard to the question of the sanitary quality of the produce 

grown on a sewage field, the experience of Berlin and Paris indicates 

that there need be no serious danger of the spread of disease from irrigated crops. The writers believe, however, that fruits and vegetables to be eaten raw should never be so treated; and McGowan, Houston, and Kershaw (R. S. C., 1904 c) would limit sewage farms to stock 

raising, saying: ;

We are, on the whole, not in favor of sewage farms being utilized for the raising of crops 

for human consumption.

Iii the western part of the United States the conditions for sewage 

farming are specially favorable. In the arid regions some form of 

irrigation is essential and the manurial value of sewage is reenforced 

by its water value. The first plant in this country was laid out at 

Cheyenne, Wyo., in 1883, and to-day there are a score or more of sewage farms in operation, of which those at Los Angeles and Salt Lake 

City are the largest. The experience of Los Angeles is of considerable 

'interest as indicating the value of sewage in such a region. Prior to 

1889 the sewage from the city, amounting to 7 million gallons, was 

carried to the so-called Vernon district, where it was taken by the 

South Side Irrigation Company and distributed to adjacent farms. 

So useful did the sewage prove that the value of the land rose from 

$2.50 an acre to from $15 to $25. A boom followed, house lots were 

developed, and the population so increased that the sewage, which 

had built up the district, became a nuisance and had to be taken 

elsewhere.

In the East the problem of sewage irrigation takes on a different 

aspect. The high cost and poor quality of land and the heavy rains 

of spring and autumn combine to make the success of such a venture
SEWAGE TREATMENT BY CHEMICAL PRECIPITATION. 29

more than problematical. It is true that the waste of valuable 

manurial elements is unfortunate, and authorities like Rafter (1897) 

have been strongly moved by such considerations. The saving of 

organic nitrogen, however, appears to-day in a less important light 

than formerly, since we know that its dissipation may be made good 

from the ocean of the atmosphere by the activities of the nitrogenfixing bacteria. At any rate the question is one which must be judged 

on a basis of dollars and cents. There are valuable elements in sewage, 

as there is gold in sea water; but if it costs more to save them than 

they are worth after they are saved we must let them go. On the 

Pacific coast sewage farming is profitable. In the East, under present 

conditions, it is unlikely to prove so.

TREATMENT OF SEWAGES BY CHEMICAL PRECIPITATION.

Parallel with the development of broad irrigation there grew up a 

method, or a group of methods, for the utilization of the useful elements in sewage on a different principle. The idea that sewage sludge 

may be valuable is so discredited to-day that it is difficult to believe 

that the first attempts at chemical treatment were, made with a view 

to the recovery of its constituents in a "portable and consequently 

marketable form." Such, however, was the object with which numerous processes were devised in the early sixties. Between 1856 and 

1876 no less than 417 patents were issued in England for processes 

connected with the chemical precipitation of sewage.

The various methods of treatment consist, as a rule, of two stages 

the addition of some substance which will produce a flocculent precipitate, and the sedimentation of the mixture to separate the heavy 

sludge from the supernatant liquid. The precipitants used are various, but the active elements in most cases are salts of lime, aluminum, 

or iron. The rivers pollution commission in its report of 1870 discussed the action of lime, lime and chloride of iron, sulphate of aluminum, Sillar's "ABC" mixture (alum, blood, and clay with other substances), and Holden's compound (iron sulphate, lime, and coal dust). 

Hazen (1890) in 1889 carried out for the Massachusetts State board 

of health an elaborate series of experiments, from which it appeared 

that either ferric salts or a mixture of ferrous sulphate with lime 

proved most satisfactory. In the first case ferric hydroxide was precipitated, and in the second case ferrous hydroxide, calcium carbonate, and various insoluble organic lime salts. Ferrous sulphate alone 

gave less satisfactory results, as did also sulphate of aluminum.

Exhaustive studies of various precipitants were made by Dibdin 

in connection with the treatment of the sewage of London, results and 

cost of different processes being worked out in great detail. All suspended matter could be removed, and with regard to the dissolved 

organic matter the efficiency ranged from a removal of 10 per cent
80 THE PUEIFICATION OF BOSTON SEWAGE.

with 52 parts per million of lime to a removal of 31 per cent with 784 

parts of lime, 168 parts of ferrous sulphate, end 560 parts of sulphate 

of aluminum, and a remove! of 52 per cent with 9,800 parts of lime, 

1,400 parts of ferrous sulphate, and 700 parts of sulphate of aluminum. The annual cost for a daily flow of 157 million gallons was estimated at $60,000 for the first result quoted, $400,000 for the second, 

and nearly $50,000,000 for the third. In general it was found that 

lime was the best b_ sis, and for use in combination with it iron salts 

were preferable to those of aluminum. The combination finally 

determined on was 56 parts of calcium oxide (4 grJns per gallon) 

with 14 parts of ferrous sulphate (1 grain per gallon). After the 

addition of precipitants the sewage is allowed to settle in tanks where 

it either remains quiescent for a time or flows through slowly and 

continuously. The second or continuous method is most satisfactory, 

and a capacity of from one-half to twice the daily flow is sufficient for 

sedimentation. For a complete separation on a small area a tank of 

special form is sometimes used, whose bottom is an inverted cone in 

which the sewage passes upward, its flow supplementing the action of 

gravity. At a certain level in the tank the precipitated material 

collects, so as to form a sort of filtering layer through which the 

ascending sewage must pass. A tank of this form (Rockner-Rothe 

type) was installed at the World's Columbian Exposition in Chicago 

in 1893 (Hazen, 1894); it was practically identical with the Dortmund 

tank extensively used in German plants for the treatment of industrial 

wastes.

The results to be expected from the chemical treatment of sewage 

may be learned from the experience of London. The sewage of the 

city was originally discharged from the various sewers directly into 

the Thames, producing a nuisance which culminated in the historic 

stink of 1858. To cope with these conditions a system of intercepting 

sewers was completed in 1865 which discharged the sewage from the 

district north'of the river at Barking Creek and that from the south 

side at Crossness, about 12 miles below London Bridge. This 

arrangement proved satisfactory for a time, until the volume of sewage had too greatly increased. By 1875, however, it became necessary to discharge part of the flow on the flood tide; the liquid carried up 

the river and the solids deposited on the shores became once more a 

serious nuisance. In 1882 the metropolitan sewage commission was 

appointed and advised the removal of solid matter from the sewage 

by deposition or precipitation. In accordance with its recommendations precipitation works were constructed at both outfalls, the 

sewage being treated, as noted above, with 56 parts per million of 

calcium oxide and 14 parts per million of ferrous sulphate. At the 

present time the same system is still in force. The sewage from the 

city of 4,500,000 inhabitants amounts to 280 million gallons per day,
SEWAGE TREATMENT BY CHEMICAL PRECIPITATION. 31

and 7,200 long tons of sludge are daily carried 50 miles out to sea by 

a fleet of six dumping boats. The total cost of treatment is nearly, 

$900,000 a year (Baker, 1904). The results of the chemical treatment 

for London are indicated in Table VII and show a removal of somewhat over three-fourths of the suspended matter, but only slight 

improvement in the soluble constituents. The effluent is by no means 

purified. It is merely so improved by the removal of most of its 

solids that its discharge into the Thames is for the time being permissible.

TABLE VII. Resvlts of chemical precipitation at London, 1894 (Dibdin, 1903).

[Parts per million.]

Source.

Northern outfall . . 

Southern outfall .. .

Material.

lEffluent.. ........... -.-.--.-

Suspended 

solids.

417 

99 

441

87

Dissolved material.

Total.

862 

910 

1,300 

1,420

Oxygen 

consumed in 

4 hours 

at 80° F.

44.5 

46.2 

53.1 

44.5

Nitrogen as 

Free ammonia.

35.6 

36.9 

34.8 

28.9

Albuminoid ammonia.

4.1 

4.2 

4.9 

3.9

At Manchester conditions appeared somewhat more favorable for 

precipitation on account of the presence of certain chemicals in the 

factory wastes, and only 31 parts of calcium oxide and 17 parts of 

ferrous sulphate were added. The results with respect to the total 

organic constituents are indicated in Table VIII. The figures are 

five-year averages of the results of analyses made twice a day on 

hourly samples. The purification of the effluent proved inadequate 

to meet local conditions, and the system has been abandoned in favor 

of newer biological processes.

TABLE VIII. Results of chemical precipitation at Manchester, England, 1900-1904 (Manchester, 1900-1904).

[Parts per million.]

Material. consumed 

in 4 hours.

116

76.4

Oxygen

consumed 

in 3 minutes.

56.7

37.2

Nitrog

Free ammonia.

23.6

24.2

en as 

Albuminoid ammonia.

5.9

3.9

At Birmingham a number of chemical processes were tested in 

1871 and found unsatisfactory. Watson, the present engineer of the 

drainage board, comments: .

I venture to say that a similar conclusion would have been arrived at if the committee, 

instead of trying only seven chemical processes, had tried all the 454 processes which were 

patented previous to 1886. [Watson, 1903.]
32 THE PURIFICATION OF BOSTON SEWAGE.

At Salford a thorough test of 13 different precipitants yielded no 

satisfactory effluents.

The disposal of the sludge is a serious problem in chemical precipitation. Its quantity is considerable, amounting to 26 tons per 

million gallons of sewage at Salford, 21 tons per million gallons at 

Manchester, and 60 tons per million gallons at Chorley. Of this crude 

sludge 90 to 95 per cent is water. Wallace found the composition of 

the air-dried residue from eight different English plants to average 

12 per cent of water, 26 per cent of organic matter, 1 per cent each of 

nitrogen and phosphoric acid, and 35 per cent of sand (Robinson, 

1896). Far from being marketable, as the projectors of the process 

dreamed, the disposal of this sludge generally involves considerable 

expense. In 1894 a canvass by the local government board showed 

that of 234 places using chemical processes only 30 were able to obtain 

any revenue from sludge. In some German plants the sludge is 

evaporated and burned for generating gas. The usual course, however, is to compact it in filter presses and dispose of the press cake 

by burning it or burying it in the ground.

On the whole, chemical precipitation has become somewhat discredited of recent years. The cost of chemicals is considerable, the 

disposal of the sludge is vexatious, and the effluent produced is imperfectly purified and always subject to secondary putrefaction. 

Except under special conditions this treatment can be considered 

only a preliminary process, to be followed by some final biological 

treatment which shall effect real purification. Even in this role the 

process is generally less applicable than the septic tank, since, as 

compared with the latter, it produces results only slightly better with 

a considerable additional cost for chemicals and with an increase in 

the quantity of sludge.

In special cases, however, chemical treatment still has its application. While most English cities are abandoning chemical precipitation for some newer process, Glasgow is installing new tanks which 

will eventually handle 140 million gallons of sewage daily, using lime 

and sulphate of alumina as precipitants. The experience of Worcester, Mass., is of considerable interest in this connection, since 

there, too, chemical precipitation is apparently likely to be maintained. In 1867 the city of Worcester was permitted to use as a common sewer Mill Brook, which discharges into Blackstone River. In 

1880 vigorous complaints began from Millbury and other towns below 

that the stream was so foul as to be a nuisance and a danger to the 

health of the community. Phineas Ball, Colonel Waring, and others 

reported various plans for relief, and in 1882 the State board of 

health recommended the installation of intermittent filters. In 1886 

the legislature ordered that the city should remove from its sewage 

before discharge into Blackstone River "the offensive and polluting
SEWAGE TKEATMENT BY CHEMICAL PKECIFIXATION. 33

properties and substances therein, so that after its discharge into said 

river it shall not create a nuisance which might endanger the public 

health." A chemical precipitation plant was duly installed in 1890, 

but the condition of the river remained bad. In 1895 Millbury 

brought suit against Worcester on the ground that the act of 1886 had 

not been complied with. After full expert discussion it appeared 

that the condition of the river was in part due to the past pollution 

which had for years accumulated in its bed as sewage mud, and in 

part to the imperfectly purified chemical effluent still being discharged. The courts declared that the city had acted in good faith 

in attempting to carry out the act of 1886, but ordered that it should 

take further steps to comply with its provisions. Since that date 

sand areas for intermittent filtration have been progressively udded 

for the final purification of the chemical effluent. It is possible in 

this case that chemical treatment is the best available preliminary 

process, since the city sewage contains free sulphuric acid and sulphate of iron from the wire works which aid the chemical process 

and perhaps interfere with bacterial action.

In 1904, 4,622 million gallons of sewage were received at the Worcester works, of which 4,227 million gallons were treated chemically. 

Sixjmndred million gallons of the chemical effluent and 395 million 

gaSB|s of raw sewage were treated on sand filters. Lime is the only 

precipitant used, in the amount of 120 parts per million, sufficient 

iron being already present in the sewage to complete the reaction. 

For every million gallons of sewage treated 5,756 gallons of wet sluc'ge 

are obtained, containing 6.93 per cent of solids. After pressing, this 

is reduced to 5.7 tons of pressed sludge containing 28.9 per cent of 

solids. The cost of pressing and sludge disposal amounts to over 

$5 per million gallons. The analyses of sewage and effluent from 

1894 to 1904. show that the yearly removal of the total albuminoid 

ammonia has varied from 46 to 63, averaging 52 per cent; of total 

oxygen consumed from 37 to 59, averaging 51 per cent; of suspended 

albuminoid ammonia from 83 to 98, averaging 93 per cent; and of 

suspended oxygen consumed from 77 to 89, averaging 82 per cent 

(Worcester, 1905). The results for 1904 are shown in Table IX.

TABLE IX. Results of chemical precipitation at Worcester, Mass., 1904 (Worcester, 1905).

[Parts per million.]

Material.

Nitrogen as 

Free 

ammonia.

15.9 

14.4

Albuminoid 

ammonia.

Total.

6.8 

3.4

Soluble.

2.5 

3.1

Oxygen consumed 

in 2 minutes' 

boiling.

Total.

96.9 

54.2

Soluble.

59.7 

43.1

IRE 185 06 3
THE PURIFICATION OF BOSTON SEWA'GE.

Another large American precipitation plant is that at Providence, 

R. L, where since the sewage effluent is discharged into a tidal estuary 

the removal of suspended solids alone is all that is necessary. Precipitation was recommended by S. M. Gray after an exhaustive investigation in 1884, but the plant was not finally installed until 1902. 

Comparative statistics for the operation of the Worcester and Providence purification works in 1903, copied from Fuller, are given in 

Table X.

TABLE X. Statistics of chemical precipitation at Worcester, Mass., and Providence, R. I.,

1903 (Fuller, 1905a).

Applied lime. ........................................

Applied copperas ....................................

Percentage of removal:

Suspended organic matter by albuminoid ammo 

Wet sludge:

Dry solids in sludge:

Cost of sludge pressing and disposal:

Cost of chemical precipitation (labor and supplies) p 

Total cost of operation:

Cost per ton:

..................do.........

! pounds per million gallons .

pounds per million gallons.

ftons daily. ...............

 ' \percentage of dry solids. .

Worcester.

122, 000 

15.55 

14.39 

5,250 

871 

6.1 

0 

0 

5.5

51.69 

91.58

67,200 

.4671 

7.44 

33.5 

69 

30.3

20.80 

1.45 

62

$3.39 

$4.91 

$4.01

$8.92 

10.384

$6.00

S0.23J

Providence, o

170,000 

20. 38 

20 

7. 300 

606 

4.2 

65 

.46 

11.1

o49.80 

082.54

95, 600 

.4776 

5.37 

23.6 

76 

28.25

21.40 

1.07 

46

$2.27 

$2.44 

$3.31

$5.75 

$0.248

$6.90 

$7.80 

$0.15

o Providence sewage well screened before treatment.

Before leaving the subject of chemical treatment it will be well to 

refer briefly to certain special processes which have been suggested 

and adopted in exceptional cases without finding general application. 

For example, with the Liernur system of sewerage in use in certain 

Dutch and Belgian cities, which lie at too low a level for gravity systems, the excreta diluted with a small volume of water are drawn off 

by suction through a system of tight sewers, and sewage of this type 

has been handled by direct evaporation, the residue being used as fertilizer. Its application is naturally limited (U. S. Dept. State, 1895). 

The Degener process applied in some German cities involves mixture 

of the sewage with crushed lignite, precipitation with ferric sulphate, 

pressing of the sludge, and treatment of the effluent with bleaching 

powder. The process is costly, but at Potsdam and Tegel is said to
INTEKMITTENT SAND FILTRATION OF SEWAGE. 35

produce a very perfect effluent (Grunbaum, 1902). The bleaching 

powder in this process is supposed to disinfect the final effluent; and 

the same end is aimed at in a number of chemical processes based on 

the use of such substances as ozone and the oxychlorides. The 

Webster process allowed sewage to flow between iron electrodes so 

that the chlorides present were electrolyzed, liberating free chlorine 

and oxygen and forming iron salts. In the Hermite process a 

stronger action was obtained by electrolyzing sea water and adding it 

to the sewage (Rideal,1901). Considerable interest has been manifested in these and similar methods during the last year. Disinfection 

processes, however, ignore the fundamental problem of sewage disposal, which is the production of an oxidized, not of a sterile, effluent. 

Until a really purified and stable effluent has been produced disinfection is a step in the wrong direction.

An interesting method has been suggested by Adeney and installed 

by Kaye. Parry at Dundrum, Chapel-Izod, and other Irish towns. It 

aims at the addition of chemicals in such a way as to favor rather than 

to check biological action. The sewage is first precipitated byoxanite, 

which is a crude sulphate of manganese mixed with the higher oxides 

of that element, and then nitrate of soda is added to the supernatant 

liquid. The manganese supplies the sludge with oxygen, so that a 

rapid aerobic fermentation occurs and the nitrate performs the same 

function for the effluent.

PURIFICATION OF SEWAGES BY INTERMITTENT FILTRATION THROUGH

SAND.

The only general method for the purification of sewage is its oxidation by micro-organisms. We have seen how this process has been 

empirically utilized in dilution and in broad irrigation. Its scientific 

principles were grasped by a few investigators at an early date. 

About 1865 Alexander Mueller described the purification of sewage as 

a process of digestion and mineralization carried out by minute animal 

and vegetable organisms (Rideal, 1901). In 1878he took out a patent 

for a "process for the disinfection, purification, and utilization of 

sewage by the scientific cultivation of yeastlike organisms" (Bruch, 

1899). In 1877 the fact that the purification of sewage is due to 

bacteria was demonstrated by Schloesing and Muntz in a series of 

experiments in which it was shown that nitrification did not occur in 

soils sterilized by heat or chloroform (Schloesing and Muntz, 1877). 

Warington reported further suggestive results along this line in 1892.

These suggestions appear to have made little impression in Great 

Britain and the United States. Meanwhile, however, the practical 

side of the subject was undergoing an important development in 

England. In 1870 Sir Edward Frankland carried out a series of 

significant experiments, the results of which were published in the
36 THE PURIFICATION OF BOSTON SEWAGE.

first report of the rivers pollution commission. Sewage was filtered 

both upward and downward through various soils at different rates, 

and it was shown that a good effluent could be obtained by downward filtration through coarse gravel at a rate of 0.08 million gallons per acre per day, while upward filtration produced only a foul 

and turbid effluent. Doubling the rate interfered with the purification, and it was seen that a resting or aerating period between the 

applications of sewage was a necessity. The principle of the process as a chemical oxidation of organic matter to water, carbon 

dioxide, and nitrates was clearly recognized, as well as the practical necessity for intermittency in operation. The cycles in the 

life of a sewage filter were compared to the inspirations and expirations of the lungs (rivers pollution commission, 1870).

These researches indicated that with suitable soil the process of 

broad irrigation might be made more intensive, the growing of crops 

being subordinated to the treatment of sewage at a more rapid rate. 

This principle was quickly applied on a practical scale by J. BaileyDenton, who constructed an intermittent filter at Merthyr Tydvil, 

Wales, in 1871. Beds 20 acres in area were furrowed, cropped, and 

operated at a rate of 0.06 million gallons per acre per day. This 

rate was later reduced to 0.016 by the addition of more irrigation 

land, but the original plant worked admirably and was of importance as a practical demonstration of Frankland's experiments on a 

large scale (Bailey-Denton, 1882). Neither Frankland nor BaileyDenton, however, understood the biological nature of the process. 

The latter said of his filters in 1882:

The assimilative powers of growing plants are brought to bear on the fertilizing elements of the sewage at the same time that the percolation of the sewage through the 

soil brings it in contact with the atmospheric air pervading the soil and renders it harmless by oxidation, as explained by the rivers pollution commissioners.

Altogether, it is clear that in the early eighties the theory of sewage oxidation was understood by French and German investigators. 

On the other hand, the practice of intermittent filtration had been 

empirically worked out in England by Frankland and Bailey-Denton. 

The laboratory investigations, however, were academic and the practical data incomplete. To combine a sound conception of the biological principles involved with a study of the engineering data of 

operation on a practical scale was left for American investigators. 

English sanitarians have not been slow to recognize that "it was 

primarily due to the Massachusetts State board of health, who 

began their investigations in November, 1887, and have continued 

them ever since, that the bacterial treatment of sewage has been 

forced on public attention" (Watson, 1903). For the mass of data 

accumulated and the thoroughness with which these data were 

analyzed, as well as for the almost revolutionary effect which they
INTERMITTENT SAND FILTRATION OF SEWAGE. 3*7

worked in sewage practice, the Massachusetts experiments well 

deserve the term of "classic," by which they are so commonly 

designated.

In 1886 the legislature of Massachusetts charged the State board 

of health with the advice of cities and towns, corporations, and 

individuals as to water supply and sewage disposal and ordered it 

to collect information and conduct experiments on the purification 

of sewage. Hiram F. Mills, a distinguished hydraulic engineer and a 

member of the board, organized the investigation, with the assistance of T. M. Drown and W. T. Sedgwick, both of the Massachusetts Institute of Technology, as chemist and biologist, respectively. 

An experiment station was fitted up in 1887 on the bank of Merrimac River at Lawrence, under the immediate charge of Alien Hazen. 

Here ten circular cypress tanks 17 feet in diameter and 6 feet deep 

were filled with various filtering materials sand, gravel, peat, river 

silt, loam, garden soil, and clay and dosed with sewage pumped 

from the city sewer. The results exceeded the hopes of the investigators. By passage through a fairly porous soil on the intermittent plan, one dose being applied every twenty-four hours, sewage 

could be converted into a clear and completely nitrified effluent. 

Peat and garden soil proved too impervious and, although operated 

at very slow rates, clogged. In this condition the air supply was 

cut off and nitrification failed. All the other filters showed good 

purification at rates of from 0.02 to 0.1, the quality of the effluents 

being equal in many cases to that of well waters in use in the city 

of Lawrence.

The true nature of sewage purification as a bacterial oxidation 

was clearly brought out in these experiments. Intermittency of 

application supplies the needed oxygen, and any fairly porous material will serve as a resting place for the active bacteria.

The experiments with gravelstones give us the best illustration of the essential character of intermittent filtration of sewage. In these, without straining the sewage sufficiently to remove even the coarser suspended particles, the slow movement of the liquid 

in thin films over the surface of the stones, with air in contact, caused to be removed 

for some months 97 per cent of the organic nitrogenous matter, a large part of which 

was in solution, as well as 99 per cent of the bacteria, which were of course in suspension, and enabled these organic matters to be oxidized or burned, so that there remained 

in the effluent but 3 per cent of the decomposable organic matter of the sewage, the 

' remainder being converted into harmless mineral matter.

The mechanical separation of any part of the sewage by straining through sand is 

but an incident, which, under some conditions, favorably modifies the result; but the 

essential conditions are very slow motion of very thin films of liquid over the surface of 

particles having spaces between them sufficient to allow air to be continually in contact 

with the films of liquid.

With these conditions it is essential that certain bacteria should be present to aid in 

the process of nitrification. These, we have found, come in the sewage at all times of 

the year, and the conditions just mentioned appear to be most favorable for their efficient 

action and at the same time most destructive to them and^to all kinds of bacteria that 

are in sewage. [Mills, 1890.]
38 THE PURIFICATION OF BOSTON SEWAGE.

The organisms active in the nitrifying process, isolated independently by Winogradsky in France and by Richards and Jordan (1890) 

at Lawrence, have been studied by a number of bacteriologists, of 

whom Schultz-Schultzensteiii (1903) and Boullanger and Massol (1903) 

are perhaps the latest. The necessity for an alkaline base for nitrification, known to agriculturists since the time of Varro, has been confirmed by these observers, who find that free acids, organic or inorganic (0.5 per cent), and nitrates or nitrites in 1 to 3 per cent solution, 

quickly check the work of the organisms. A marked excess of free 

ammonia or of any alkali has the same effect. Thus Warington found 

that a 12 per cent solution of urine having a maximum alkalinity of 

446 parts of ammonia as carbonate would stop nitrification. At 

Burton sewage containing 100 parts of free lime would not nitrify till 

it was neutralized (Barwise, 1904). Rideal also notes a harmful 

effect due to carbon dioxide, and Letts believes that sodium chloride 

from sea water hinders the formation of nitrates at Belfast (R. S. C., 

1902 a). The optimum temperature for the reaction lies between 28° 

and 37° C. It is stopped in the neighborhood of 50° C.

Later work at Lawrence, where numerous small experimental filters have been operated since 1890, has brought out further details of 

the process of intermittent filtration. In the 1891 report, prepared 

by Alien Hazen, the chemist in charge of the station, it was shown 

that while most of the organic matter of the sewage is actually 

destroyed and while there is no important storage in the depths of 

the filter, its surface accumulates a certain amount of stable organic 

matter which must be removed at intervals. It was made apparent 

that in severe winter weather the quality of the effluent, while considerably deteriorated, was still reasonably satisfactory. The maximum rate at which sewage could be conveniently applied varied from 

0.03 with sand of an effective size of 0.03 mm. to 0.06 with sands of 

0.06 to 0.35 mm., 0.1 with sands of 0.17 and 0.48 mm., and 0.2 with 

gravel of 5 mm.

One of the strong points about the Lawrence experiments has been 

their continuity for a sufficient period to show the long life of intermittent filters, four of the original outdoor filters having been operated for seventeen years. A comparison of the effluents during the 

first seven and the last nine years of operation has been compiled 

from the reports of the State board and is shown in Table XI. Although, with a considerably increased concentration of sewage the 

effluents have deteriorated, yet the percentage purification has only 

slightly decreased, and the effluents are still of good quality.
INTERMITTENT SAND FILTBATION OP SEWAGE. 39

TABLE XI. Results of intermittent filtration at Lawrence, Mass., in successive periods

(Massachusetts, 1895-1903}.

1888-1894 

Filter No. 1 .........

Filter No. 2.... .....

Filter No. 4 .........

Filter No. 6. ........

Filter No. 9A.. ......

1895-1903. 

Filter No. 1. ........

Filter No. 2 .........

Filter No. 4. ........

Filter No. 6 .........

Filter No. 9A........

Quantity 

of sewage 

applied 

(gallons 

per acre 

per day).

76,000 

34,000 

27,000 

47,000 

74,000

51,000 

30,000 

16,000 

51,000 

52,000

Temperature (°F.)

53 

52 

52 

53 

53

55 

54 

54 

54 

54

Analyses (parts per million) .

Nitrogen asFree 

ammonia.

2.3 

1.7 

1.7 

1.9 

4.9 

18.8

8.6 

5.8 

2.4 

7.6 

8.8 

32.6

Albuminoid 

ammonia.

0.4 

.1 

.2 

.3 

.3 

5.5

.6 

.3 

.2 

.6 

.5 

5.9

Nitrates.

16.8 

15.9 

10.4 

16.4 

18.3

25.8 

28 

26.9 

26 

26.7

Nitrites.

0.18 

.15 

.02 

.34 

.08

.23 

.10 

.03 

.31 

.09

Oxygen 

consumed in 2 

minutes' 

boiling.

4.7 

1.7 

3.7 

3.2 

3.2 

36.2

6.6 

3.3 

1.8 

5.8 

5.6 

41.3

Chlorine.

68.5 

65.4 

59.9 

68.1 

80.2 

68.4

94 

91.4 

86.1 

90.8 

89.6 

91.8

The early Massachusetts experiments led at once to practical developments. In the 1887 and 1888 reports of the board of health preliminary results were announced, and in 1889 the board reported that 

a plan suggested for the disposal of the sewage of the Mystic Valley 

on the Saugus marshes was impracticable on account of the peaty 

nature of the soil. Also in 1889, in accordance with the favorable 

results obtained at Lawrence by filtration through coarse sand, the 

first large intermittent filtration area in the State was laid out in the 

town of Framingham. Gardner and Marlboro followed in 1891, 

and at the same time the first filter in Connecticut was built at 

Meriden.

In 1903 (Massachusetts, 1904) the State board of health of Massachusetts discussed the results of the operation of 23 plants in the Commonwealth. All made use of intermittent filtration, and the report 

concludes that 

The ready availability of sand and gravel .areas naturally adapted for the purification 

of sewage, the simplicity of the process, and the small cost of maintenance have made this 

method of purification the most advantageous for adoption in practically all the cases in 

which sewage-purification works have been found necessary, and the resulting effluents 

turned into the stream have been satisfactory in all cases where the works are of sufficient 

capacity and have received proper care.

The principal analytical data from the report are shown in Table 

XII, which gives a fair idea of the operation of the intermittent process. It will be noted that the rates vary in general from 0.05 to 0.1 

and that the effluents are in most cases of satisfactory quality. They 

are superior in almost every instance to those obtained at the English 

sewage farms, as shown in Table VIII.
TABLE XII. Statistics of intermittent filtration in Massachusetts (Massach

Place.

Gardner (Gardner 

system) .

Date of 

construction.

1898 

1894 

1899 

1898 

1889 

1891 

1892 

1894 

1890 

1805 

1890 

1899 

1897 

1899 

1891 

1898

Average 

daily 

flow 

(million 

gallons) .

0.135 

.878 

.785 

.312 

.652 

.302 

.150 

.030 

1.100 

.566 

1.456 

.350 

.375 

.075 

.282 

1.080

Area of 

filter 

beds 

(acres) .

3. 65 

21.48 

23.5 

3.3 

19.9 

2.5 

2.3 

.36 

11.2 

11.1 

21.67 

7.25 

9.3 

3.6 

4 

8.77

Rate 

(million 

gallons 

per acre 

per day) .

0.0342 

.0409 

. 0334 

.0945 

'. 0328 

.1208 

.0652 

.0833 

.0982 

.0510 

.0672 

. 0483 

.0403 

.0208 

.0705 

.123

Population contributing 

sewage.

3,600 

25,000 

10,000 

1,200 

7,500 

3,500 

2,000 

500 

10,000 

4,000 

15,000 

2,200 

3,000 

800 

3,000 

122,000

Preliminary treatment.

.....do................................

.....do................................

.....do................................

.....do................................

.....do................................

.....do ................................

.....do................................

Screening; partial sedimentation....

M

/Sew

Eff

Sew

Eff

Sew

Sew

Eff

[Sew

\Effl

JSew

\Effl

Sew

Eff

Sew

Eff

Sew

Eff

Sew

Eff

JSew

\Eff

JSew

\Eff

JSe

\Eff

/Sew

JEff

JSew

JEff

/Sew

\Eff

a Worcester analyses of daily samples analyzed weekly from December 1,190
INTERMITTENT SAND FILTRATION OF SEWAGE. 41

With regard to the comparative results of different Massachusetts 

plants the following points may be noted: The poor effluents at 

Westboro and Gardner are due partly to careless operation, the sewage being allowed to run on continuously for days. At Clinton the 

applied sewage is very strong. At Leicester, Andover, and Hopedale 

the board attributes results below the average to the fact that the 

sewage is stale or septic when applied. At Worcester the sewage is 

strong, and it is probable that its acid-iron waste interferes somewhat 

with the process of nitrification. It has been thought best, at any 

rate, not to attempt to treat crude sewage, as was done in the experiments included in Table XII. The comparative results of filtration 

with and without chemical precipitation, as shown in Table XIII, 

indicate the great advantage of special treatment.

TABLE XIII. Results of intermittent filtration of crude sewage and chemical effluent at 

Worcester, Mass. (Worcester, 1905).

[Parts per million.]

Material.

Nitrogen as 

Free 

ammonia.

18 

10.9 

20.1 

.8

Albuminoid ammonia.

Total.

8.1 

.9 

3.6

.7

Dissolved.

3.8 

.9 

3.2

.7

Nitrates.

0.6 

2 

1.1 

4.1

Nitrites..

0.1 

.3 

.4 

.2

Oxygen consumed.

Total.

138.7 

18.1 

56.5 

9.5

Soluble.

79.5 

18.1 

44.4 

9.5

In. construction the Massachusetts niters are simple, being built in 

general of natural glacial drift. The subsoil is removed, being used 

to form embankments between the beds, and the sand is not disturbed except for the laying of underdrains. Beds, as a rule, are 1 

acre in area, the sewage being distributed through branched wooden 

carriers of sizes so varied as to secure approximately uniform distribution. This point is of much importance, since the passage of large 

volumes of sewage through a portion of a bed necessarily leads to 

poor results. At many plants, as at Framingham, Natick, and 

Brockton, crops have been grown on the beds. At Brockton this 

practice has recently been abandoned, since it was found to cause an 

accumulation of fine organic matter detrimental to the surface.

The effect of winter weather on the process has not been found to be 

serious. The actual freezing of the surface is prevented by furrowing 

the beds, so that a layer of ice forms on the top of the ridges, leaving 

an open space between them. Here the sewage flows, its warmth 

being sufficient to keep the surface open under the covering of ice. 

The process of nitrification is, however, considerably interfered with 

by the direct action of cold, as is shown on page 131 of this paper. 

This fact, combined with the impossibility of scraping off surface
4 THE PUBLICATION OF BOSTON SEWAGE.

accumulations during severe weather, leads to a general clogging of 

the filters during the winter months. With ample capacity this 

period may easily be tided over. Goodnough said in 1904 (Winslow, 

1905 b):

Of the 1 5 sewage-disposal plants of considerable size where works were originally provided 

for the treatment of all of the sewage, all of the sewage is treated at all times at 6 places, or 

more than one-third of those having purification works, and very little sewage is discharged 

untreated at 6 of the remaining places, leaving only 3 places out of the 15 at which, at 

the present time, any considerable quantity of sewage is allowed to escape without treatment.

The accumulation of a certain amount of material on the surface of 

the beds is a necessary feature of the process of intermittent filtration as practiced in Massachusetts. This material, appearing in the 

form of a dry cake of a stable and inoffensive character, scarcely deserves the name of sludge, by which it is frequently designated. 

However, it necessitates a considerable expense in operation. The 

beds must be frequently raked and harrowed and occasionally plowed 

and scraped. At Pawtucket it has been found in ten years that for 

every million gallons of sewage 8.39 cubic yards of material (including sand) were removed from the surface (Pawtucket, 1904). At 

the Brockton plant, which is admirably designed and operated, full 

data are published on this point. In 1904 a daily flow of 900,000 

gallons from a population of 40,000 was treated on 211 acres of sand. 

A storage well at the pumping station holds the night flow of sewage, 

so that the pumps are run only in the daytime. The sediment which 

collects at the bottom of this reservoir is stirred up at the end of a 

run and discharged on four special "sludge beds." The cost of labor 

on the surface of all the beds during 1904 was $2,932, and the total 

cost of maintaining the area $4,412 (including gate tending, care of 

roadways, etc.), amounting to over $15 per million gallons (Brockton, 1905). The expense of maintenance at 16 Massachusetts plants 

varied in 1903 from $0.61 per million gallons at Natick to $21.92 at 

Stockbridge (Massachusetts, 1904). The Natick beds received practically no care except in connection with cropping, but operated satisfactorily. The next lowest figures were $2.45 at Pittsfield and $2.60 

at Marlboro (large plants) and $2.87 at Concord (weak sewage). The 

costs at Clinton, Southbridge, Spencer, Westboro, and Worcester 

were between $3.91 and $7.80; at Gardner, over $9 at each of its two 

areas; at Brockton and Leicester, $11; and at Andover, $13.98.

TREATMENT OF SEWAGES IN THE SEPTIC TANK.

While the process of intermittent filtration was being scientifically 

developed in Massachusetts, English sanitarians were beginning to 

treat sewage on a totally different principle that of anaerobic putrefaction. At an early period it had been noticed that in cesspools
SEWAGE TREATMENT IN SEPTIC TANK. 48

some action took place which led to the dissolution of solid matter. 

In Paris, where until 1880 various receptacles were largely used by 

individual householders for the reception of excreta, there might be 

found "the fosses fixees, from which the matter was raised by metallic vessels or vacuum pumps; the fosses seches, used in the barracks; the tinettes filtres or filtrantes, which permitted the liquids to 

escape and reduced the refuse to one-fifth part, and the vidange automatique, invented by Mouras to do away with the necessity for even 

periodic removal of the solids" (Metcalf, 1901). The latter was "a 

closed vault with a water seal, which rapidly transforms all the excrementitious matter which it receives into a homogeneous fluid, only 

slightly turbid, and holding all the solid matters in suspension in the 

form of scarcely visible filaments." The action was attributed to 

anaerobic bacteria. This tank was introduced by Mouras about 

1860, was fully described by Abbe Moigno in the Cosmos les Mondes 

in 1881, and was patented in 1882. In 1883 E. S. Philbrick, an 

American sanitary engineer, described a tank "in which the solid 

particles of the sewage may become macerated and finely divided by 

fermentation." In 1891 Scott-Moncrieff constructed at Ashtead, 

England, what he called a cultivation tank, in which sewage was 

allowed to pass upward through a tank containing stone prior to passage through "nitrifying channels" of coke. The attempt to produce a purified effluent failed, but it was shown that the first or anaerobic tank exerted a remarkable dissolving action on the solid constituents. In 1893 a plant on the same plan was designed for the 

borough of Towchester. A year later, in 1894, C. N. Talbot built a 

sewage tank at Urbana, 111., in which the liquefying anaerobic action 

was observed; and a larger plant, with this definite end in view, was 

designed for Champaign, 111., in 1895 and built in 1897.

The anaerobic process of sewage purification owes its practical 

development chiefly to Donald Cameron, of Exeter, England, who 

holds much the same relation to this process that the Massachusetts 

State board of health holds toward intermittent filtration. In 1895 

he installed a water-tight covered basin for the treatment of the sewage of a portion of the city by anaerobic putrefaction and gave it the 

picturesque name of the septic tank. The sewage flowed slowly 

through the tank, taking about twenty-four hours in passage, the 

inlet and outlet being about midway between the top and bottom. 

He found that the liquid turned dark colored, while in the solids collected at the bottom an active fermentation was set up. Bubbles 

continually rose to the surface, carrying with them solid particles, 

which gathered at the surface to .form a scum, sometimes so firm and 

compact that a man could stand upon it. This scum appeared and 

disappeared without any recognized reason. Meanwhile the effluent 

flowing off was freed from gross floating matter, and its total solids
44 THE PURIFICATION OP BOSTON SEWAGE.

and organic constituents were decreased to one-half and two-thirds 

their initial value, respectively. The material removed did not, 

however, merely accumulate in the tank, which was operated for 

three years without cleaning. At the end of the first year 25 tons of 

solids had been removed from the sewage, of which it was calculated 

that 5 tons remained in the tank, and this in the form of a rather 

stable peaty deposit, only one-third organic in composition (Rideal, 

1901).

The action in the septic tank is probably not the work of strict 

anaerobes, which appear to be rare in sewage, but of organisms able 

to grow either with or without the presence of oxygen. Under the 

latter condition the nature of their action is characteristic. They first 

decompose the solid materials by a lysis, which may or may not be 

hydrolysis (decomposition with the addition of water to the molecule). 

Next they decompose the dissolved molecule, producing gases on the 

onevhand and more stable peaty compounds on the other. Nitrogenous 

compounds are partially reduced to gaseous nitrogen or free ammonia,

A

FIG. 4. Seasonal variation in gas production in the septic tank.

and, together with cellulose, to carbon dioxide and marsh gas. The 

reaction is an exothermic one, evolving about 8 per cent as much heat 

energy as is left in the final products (Rideal, 1901). The amount of 

gas produced in the septic tank was found by Fowler at Manchester (1901) to be 7.5 gallons per 100 gallons of sewage, and Clark 

(1900) at Lawrence obtained concordant results. Kinnicutt and 

Eddy (1901), on the other hand, found less than half this amount 

(2.3 gallons) produced by the septic treatment of the acid-iron sewage of Worcester. The composition of the gas appears to vary widely 

at different places, but as a rule about three-fourths is methane and 

one-fifth free nitrogen. The amount of gas produced and, in general, 

the activity of septic action vary greatly with the temperature. Fig. 

4, plotted from the data given by Kinnicutt and Eddy, shows this in a 

striking manner.

The first septic tanks, like that at Exeter, were covered tightly. It 

soon appeared, however, that this type of construction is not at all
SEWAGE TKEATMENT IN SEPTIC TANK. 45

necessary to the maintenance of anaerobic conditions. If sewage be 

merely allowed to run slowly through an open tank the general reactions appear to go on just the same. At Manchester the results from 

closed and open tanks under like conditions showed no marked difference, and in similar experiments at Leeds the open tank gave slightly 

better results, as shown in Table XIV. For promoting anaerobic 

conditions tight covers are therefore needless. Covering has been 

advocated in order that the gases produced may be utilized for burning and that the temperature of the sewage may be maintained. The 

burning of the gases is picturesque but not practically important, and 

the temperature' of open tanks is never seriously lowered. At Leeds 

sewage in closed tanks lost 0.8°, in open tanks 1.6° F. For the prevention of odors and the fly nuisance and for protection against wind 

and rain a light frame roof may often be convenient.

TABLE XIV. Results from closed and open septic tanks at Leeds, England (Harrison, 1900).

[Parts per million.]

Open tank:

Closed tank:

Effluent .............................

Solids.

Total.

1,710 

1,110

1,720 

1,130

Suspended.

633 

172

666 

197

Nitrogen as 

Free 

ammonia.

23.6 

20.6

25.5 

20

Albuminoid 

ammonia.

11.3 

4.9

12.4 

5

Oxygen 

consumed 

in 4 hours 

at 80° F.

124 

54.3

131 

69.3

Scott-Moncrieff, in his Ashtead experiments, used, as already indicated, what was really a septic tank filled with stone. This principle 

has been applied in many other cases to the construction of anaerobic 

filters, lateral filters, etc., of various types. The so-called "ladder 

filters" tested at Leeds, formed by a series of trays of stone, from one 

to the other of which the sewage flowed continuously, operated on this 

principle- and very badly. At Salford, roughing filters containing 

one-fourth inch to 2-inch gravel were used for continuous filtration at 

a rate of 20 million gallons per acre per day. It was intended to wash 

these filters by upward flow with artificial aeration, but they have 

clogged seriously (Baker, 1904). At Lawrence a thorough study has 

been made of various strainers which operate with more or less continuous flow, of which further particulars are given in the second part 

of this report. All such devices, as well as the anaerobic filters installed 

at certain sewage plants in the Middle West, act like septic tanks, with 

the additional straining action due to the included material. Against 

this increased straining action must be set the tendency to clog and 

the difficulty of cleaning.

The most important point in the construction of a septic tank is its 

size in relation to the flow of sewage which is to pass through it. The
46 THE PURIFICATION OF BOSTON SEWAGE.

tank is really a sedimentation basin in which the supernatant liquid 

and the settled sludge both undergo fermentation. The construction

of special "hydrolytic" tanks, like 

that at Hampton (Baker, 1904), is 

gratuitous, since the bottom of the 

tank necessarily exhibits the hydrolytic phenomena to a high degree. 

The first requisite is that the period 

should be long enough to allow the 

maximum quantity of solids to settle out. From laboratory experiments on sedimentation it appears 

that this maximum is about 80 per 

cent and that it will be nearly 

reached by six hours' storage 

(Steurnagel, 1904). In practice

/000 v it has often been found that a longer

period is of advantage, perhaps for 

the liquefaction of suspended solids 

of too fine a character to settle out. 

The Leeds results in Table XV indicate an appreciably greater removal 

in twenty-four hours than in twelve 

hours, while further prolonging the 

period to forty-eight or seventy-two 

hours is of no advantage. The 

rules of the local government board 

require a septic-tank capacity of 

one and one-half times the dryweather flow, and actual English 

practice generally contemplates a 

twenty-four hour period. At Birmingham the septic tanks proper 

accommodate only an eight-hour 

flpw, but ten hours of additional 

storage are allowed in detritus 

tanks and a long conduit. Alvord 

(1902) and other American engineers provide shorter periods, often 

only four to eight hours, and some 

tanks operated on this principle, 

like that at Lake Forest, seem to

FIG. s Progressive effect of septic action at, work well. On the other hand, 

Lawrence, Mass. short periocis of septic treatment

at Wauwatosa and East Cleveland yield less satisfactory results 

(Winslow, 1905 b).

I

\v^

\

\ -V

\

\

\-\

 ~-~

BACTE

\

\ 

\

\

FREi 

s

^

\

ALBUM 

'foTA

.

?//!

\ 

\

\ 

\

' AMMO.

OXYGEN 

^~^

\

\ 

\

\

' \

W/4

co/vsw

-. -

WED

^~~~^^

INOID AMMONIA

"jrdr.rurJ '

. SUSPENDED \~ '

2 

PERIOD

3

DAYS
SEWAGE TKEATMEISTT TS SEPTIC TANK.

TABLE XV. Average of analyses illustrating the effect of different rates of flow through open

septic tanks (Leeds, 1905).

Nitrogen as 

Albuminoid amm ^cia . . . 

Oxygen consumed in 4 hours

12 hours' flow.

Parts 

per raillion.

1,250 

272

38.2 

6.3

74.2

Purification 

(per 

cent) .

52

22 

50

45

24 hours' flow.

Parts 

per million.

1,110

162

17.5 

5.2

68. a

Purification 

(per 

cent) .

71

24

58

49

48 hours' flow.

Parts 

per million.

1,120 

155

18.8 

4.5

61.2

Purification 

(per 

cent) .

73

19 

64

55

72 hours' flow.

Parts 

per million.

141

20.8 

4

51.1

Purification 

(per 

cent) .

76

37 

52

55

An interesting experiment was carried out at Lawrence on a small 

experimental tank with five successive compartments, each equivalent to one day's flow. The results are shown in Table XVI and are 

plotted in fig. 5. They indicate that although a steady change in 

the various constituents takes place the chief purification is accomplished in the first twenty-four hours.

TABLE XVI. Results of treatment of sewage in septic tank with Jive successive compartments, 

each holding one day's flow, April to December, 1903 (Massachusetts, 1904).

-

Effluent from first compartment (D-l ) .. . 

Effluent frofn second compartment (D-2) . 

Effluent from third compartment (D-3) . . 

Effluent from fourth compartment (D-41 . 

Effluent from fifth compartment (D-5) . .

Analyses (parts per million) .

Nitrogen as 

Free ammonia.

33.8 

36.1 

37.9 

37.5 

36.4 

35.1

Albuminoid ammonia.

Total.

4.1 

3 

2.7 

2.6 

2.2 

2.4

Tn solution.

2.3 

2 

1.9 

1.8 

1.6 

1.5

Organic 

by Kjeldahl 

method.

11.6

6.4

"""s.Y

Oxygen 

consumed in 

2 minutes' 

boiling.

40.1 

31.4 

28 

26.6 

25.9 

24.7

Bacteria 

per cubic 

centimeter.

1,800,000 

1,100,000 

950,800 

800,000 

600,000 

600,000

The septic period should not be too prolonged, since, as will be seexi 

later, the anaerobic fermentation, if carried too far, may produce an 

effluent difficult to nitrify. Furthermore, it is probable that even the 

anaerobic action itself may be checked by the concentration of wasteproducts in too long a period. The marked decrease in bacteria in 

Table XVI indicates some such toxic action. An earlier Lawrence 

experiment is also suggestive. A small septic tank was dosed, not 

with sewage, but with the more concentrated sludge from settled 

sewage. For six months the storage period was from five to fifteen 

days and sludge accumulated, filling up 60 per cent of the tank. The 

rate was then increased, so that the storage period was reduced to 

forty-nine hours, when the accumulated sludge decreased to 8 per 

cent and did not further increase for a year (Massachusetts, 1901). 

At Leeds it was found that a seventy-two-hour septic period interfered with the solution of sludge (Leeds, 1905). Clark and Gage
48 THE PUKLF1CATION OF BOSTON SEWAGE.

(1905) have found that certain types of bacteria specially active in 

sewage purification increase during the first twenty-four hours of 

septic treatment and then fall to numbers smaller than are present in 

raw sewage. It seems possible that too long a period of action may 

actually favor the accumulation of sludge while producing an effluent 

hard to nitrify. Alvord (1902) for these reasons suggests the use of 

an "elastic tank" with separate compartments, which can be included 

in or thrown out of the system to adjust it to varying conditions of 

flow and temperature.

The results of septic treatment in three English cities and at Lawrence, Mass., are shown in Table XVII, and in Table XVIII is cited 

an interesting example of septic action on an intensive scale.

TABLE XVII. Effect of septic treatment.

Place.

Exeter........

Birmingham. . . 

Lawrence......

Material.

\Tankefnuent ... 

Sewage .........

Tank effluent . . .

Tank effluent . . .

/Sewage. ........ 

\Tankemuent...

Solids.

Total.

778 

593 

I,fi90 

1,090 

1.967

1,399

7fi9 

597

Suspended.

350 

154

622 

183 

676

245

232 

107

Nitrogen as 

Free 

ammonia.

44.4 

32.5 

24.7 

21 

31.9

43.3

38.1 

37.7

Albuminoid 

ammonia.

11.7 

5.2 

13.7

18.7-

7 

3.3

Oxygen consumed.

Total.

29 

20.1

127 

58.5 

153

10S

49.5 

27.3

Dissolved.

76.1 

68.5

Kemarks.

| April to June,1897.

IFebruary, 1899, to 

] January 15, 1900. 

Septic tank No. 1, 

1901, open tank.

{

Tank A, January, 

1898, to January, 

1903.

NOTE. Oxygen consumed in four hours at 80° F. in the English results; in two minutes' boiling at 

Lawrence. Solids in Lawrence figures for year 1902 only.

Table XVIII shows the results obtained with an experimental tank 

at Brockton, Mass., in the treatment of very strong sewage pumped 

from the bottom of the receiving well during the last portion of the 

brief daily period of pumpage. The period of septic action was 

twenty-four hours. The results indicate a very high rate of purification. Boiling figures that of the suspended solids entering the tank 

45 per cent remained as sludge, 6 per cent escaped in the effluent, 16 

per cent went into solution, and 33 per cent disappeared as gas 

(Barbour, 1904).

TABLE XVIII. Results of treatment of sludge at Brockton, Mass., August and September,

1900 (Barbour, 1904}.

[Parts per million.]

Material.

Effluent.......

Volatile residue.

Dissolved.

229

285

In suspension.

1,810 

116

Fixed residue.

Dissolved.

271 

299

In suspension.

555 

31

Nitrogen as 

Free 

ammonia.

34.5 

44.1

Albuminoid 

ammonia.

Total.

42 

7.5

Soluble.

3.9 

4.6

Oxygen consumed.

Total.

396 

122

Soluble.

74.5 

65.4
SEWAGE TEEATMENT IN SEPTIC TANK. 4

In comparing the work of the large English tanks, shown in Table 

XVII, it will be noticed that the effect on free ammonia varies, this 

constituent sometimes decreasing appreciably, as at Exeter, but generally remaining fairly constant. Sometimes, as at Worcester, it 

exhibits a marked increase. The reactions in the septic tank naturally 

vary materially with the original composition and age of the sewage. 

In a very fresh sewage there is always a considerable formation of free 

ammonia by the decomposition of more complex organic bodies. If 

this process has been completed when the sewage is subjected to 

septic treatment a decrease in free ammonia may be expected in the 

tank. Albuminoid ammonia and oxygen consumed in each case fall 

to one-half or two-thirds of their initial value. The evidence accumulated by the royal sewage commission indicated that an increase 

of free ammonia is the general rule in English septic tanks, while the 

albuminoid ammonia is reduced 38 to 54 per cent at Exeter, ,50 per 

cent at Leicester, and 36 per cent at Birmingham. The oxygen consumed was reduced 25 to 33 per cent at Exeter, 50 per cent at Accrington, 50 per cent at Leeds, 36 to 60 per cent at Leicester, and 29 per 

cent at Birmingham (Martin, 1905). A curious phenomenon in certain septic tanks is the presence of oxygen or highly oxygenated compounds in the effluent in spite of the active reduction which takes 

place in the tank. Thus Barwise (1904) notes the occasional presence 

of nitrates and nitrites (up to 1 part per million) in the septic effluent 

at Exeter, and at Burnley after twelve hours' treatment in the septic 

tank oxygen was present to the extent of 1 to 3 per cent of saturation 

and nitrates up to 10 parts per million.

The most important practical result of septic treatment is the 

removal of suspended solids. Tanks at Exeter, Leeds, and Birmingham, as noted in Table XVII, show a reduction of 56, 71, and 64 per 

cent, respectively. At Leicester the removal has ranged from 60 to 70 

per cent. At Lawrence 181 parts per million of suspended solids 

were reduced to 73 parts, a removal of 61 per cent (Massachusetts, 

1904). Experiments on London sewage at the Crossness outfall 

showed that six hours' sedimentation in what was really a septic tank 

gave a reduction from 281 to 125 parts of suspended solids (November, 1900, to March, igOl^nd in another series (March to October, 

1901) from 253 to 143 parts, a removal of 56 and 43 per cent, respectively. These London results illustrate the gradual increase in suspended solids discharged in the effluent, which is sometimes noticed 

during the first year of a tank's operation. At Leeds 127 parts 

appeared in the septic effluent from March to June, 1899, 156 parts 

from July to October, and 213 parts from November, 1899, to February, 1900 (Leeds, 1900). At Huddersfield the septic effluent contained 66 parts in August, 1900, 82 parts in September, 113 parts in

IRR 185 06 4
50 THE PURIFICATION OF BOSTON SEWAGE.

October, 122 parts in November, and 117 parts in December (R. S. C., 

1902 b).

The action of the septic-tank on dissolved solids is a variable one, as 

shown in Table XIX, taken from Kinnicutt, with the addition of 

figures from a recent Lawrence report.

TABLE XIX. Removal of solids by the septic tank (Kinnicutt, 190S; Clark, 1904).

Place.

Exeter. ........................................................................

Lawrence. ......................................................................

Solids removed (per 

cent of total).

Dissolved.

- 2.57 

2.12 

12.05 

15.45 

20.67

Suspended.

56.01 

61.60 

70.37 

57.06 

25.57

It will be noticed that a slight removal of dissolved solids occurs, 

except at Exeter, reaching a considerable amount at Worcester. The 

phenomena in the case of Worcester are peculiar on account of the 

acids and iron salts in the sewage. In the first place all the reactions 

are hindered by the antiseptic action of these substances. The reduction of albuminoid ammonia is small, only 20 to 25 per cent, the gas 

production is only half that at Lawrence and Manchester, and the 

liquefaction of sludge is imperfect. In the second place the proportionate decrease of suspended solids is small and of dissolved solids 

great on account of the reduction and precipitation of iron compounds.

Granting that the septic tank effects a removal of 60 to 70 per cent 

of suspended solids under favorable conditions, the fate of the matter 

retained must next be determined how much is stored as sludge and 

how much is reduced to liquid or gaseous form. Evidence before the 

royal sewage commission indicates a destruction of the stored solids, 

amounting to 26 per cent at Manchester, 25 per cent at Birmingham 

(too low a figure, since a great deal of reducible sludge is removed 

from sedimentation chambers cleaned out weekly), 20 to 60 per cent 

at Leeds, 30 per cent at Sheffield, 35 per cent at Accrington, 40 per 

cent at Huddersfield, 50 per cent at Gl|j£gow, and 80 per cent at 

Exeter (Martin, 1905). At Saratoga the septic tank destroys 40 per 

cent of its sludge (Barbour, 1904). This value will naturally vary 

widely according to the ratio of organic to inorganic solids in the 

sewage, the inorganic solids being much less likely to disappear. In 

the London experiments the destruction' of total sludge was 41 per 

cent and of organic sludge 71 per cent (Dibdin, 1903). At Hampton 

58 per cent of the organic sludge was destroyed (Baker, 1904).

Practical experience with septic tanks yields widely varying results 

with regard to the destruction of stored solids, as indicated by the 

necessity for emptying the tanks and removing sludge. At Exeter
SEWAGE TBEATMENT IN SEPTIC TANK. 51

Cameron's original tank was operated for eight years without cleaning, but from, the present installation, with a fourteen-hour period, 

sludge is pumped out once a month. At Barrhead a tank has been 

in use for six years (twenty-four-hour period) without cleaning and 

with little deposit. At Acton (sixteen hours) a tank has been operated for fifteen months with no deposit. At Yeovil (twenty-four 

hours), Burnley (twelve hours), Sutton (five hours), and Accrington 

(twenty-eight hours) it has been found necessary to remove sludge 

about once a year. At Oldham the tank is cleaned every two or three 

months (Baker, 1904). American plants exhibit similar variations. 

The Lawrence tank has not been cleaned for six years, and in 1903 

was less than half full of accumulated sludge. At-Marion a twentyhour tank worked for two and one-half years without emptying. 

At Mansfield, with a twenty-four-hour period, admirable results have 

been obtained, only an insignificant amount of sludge having accumulated after three years of use. At Plainfield solids accumulate 

in the form of scum rather than sludge and are removed several times 

a year. Sludge and scum are probably largely interchangeable, a 

slight difference in specific gravity determining the destination of 

the,solids (Barbour, 1904). At Lake Forest (four hours), the tank 

has been operated for three years without cleaning, while at Wauwatosa (ten hours) the tank is emptied twice a year (Winslow, 1905 b). 

Of conditions in Ohio, Pratt (1904) said in 1903:

There are now in use 10 septic tanks, while plans for 14 more have been made. 

The present tanks have been in operation from one to five years. As sludge destroyers they 

have been fairly successful, but in a few cases offensive odors are created, and in some the 

effluent from the tank is probably not in the best possible state for subsequent oxidation in 

the filters. As far as can be learned the tanks have continued in use from one to two years 

without decreasing in capacity more than 25 per cent. The scum formed at the surface 

and bottom accumulation appears to remain fairly constant after reaching a certain volume"; 

but a change in the composition of the sewage or in other conditions may cause a rapid 

increase in the deposits.

On the whole, it seems necessary to conclude with Baker (1904) 

that "in the majority of septic tanks thus far built for municipalities 

the sludge must be removed at intervals of a year or less." In certain special cases, as at Exeter and Mansfield, unknown conditions 

intervene to cause a more complete destruction of the stored solids.

The chief purpose for which the septic tank has been introduced 

.is the diminution of suspended matter and the consequent lightening 

of the sludge burden. It is claimed by some experts that in addition 

to this action the anaerobic putrefaction brings the soluble constituents into a form in which they are more easily acted on by the nitrifying organisms. Martin, Cameron, and Fowler all expressed this 

opinion before the royal sewage commission (Martin, 1905). The 

writers are not aware of any data which support this contention. 

Harding and Frankland (Martin, 1905) are skeptical as to .such an
52 THE PURIFICATION OF BOSTON SEWAGE.

advantage and Dibdin (1904) wholly disbelieves in it. On the other 

hand, it is probable, as was shown before the royal sewage commission, that when not accurately regulated, "the anaerobic process may 

be carried too far, so as to interfere with the subsequent aerobic 

action" (Dibdin, 1903). Martin and Kideal minimize such interference, while Scott-Moncrieff, Woodhead, and Fowler consider it 

of great importance (Martin, 1905). It appears certain that with 

strong sewage the putrefactive process may be carried so far that its 

products will check the aerobic organisms. In experiments at Caterham an effluent was obtained containing 1,260 parts per million of 

dissolved solids, 288 parts of nitrogen as free ammonia, and 53 parts 

of organic nitrogen, which would not undergo nitrification until 

diluted (Kideal, 1901). Experience at Andover leads to the same 

conclusion. Here the sewage is strong and already twenty-four hours 

old when it reaches the disposal area. Most of it is discharged on 

sand beds without further treatment. While the beds were successfully handling raw sewage at a rate of 0.03 million gallons per acre 

per day, a small filter gave poor results with septic effluent at a rate 

of 0.04 and very bad results when the rate was increased to 0.1 (Clarkj 

1900).

From a general review of the results cited above it is not easy to 

determine just how much is to be gained by the introduction of the 

septic tank in a sawage-disposal system. With a small plant receiving very fresh sewage from a small town or an institution, it is of 

great advantage in breaking up masses of fecal matter. In such 

plants and in those which handle considerable quantities of manufactural waste the equalization of flow and composition may be of 

much importance. The latter factor, for example, carried weight at 

Manchester. These, however, are special cases. The chief point is 

that by proper septic treatment 60 to 70 per cent of the solids in sewage may be removed. When such a removal is necessary before final 

aerobic treatment, the septic tank will general!} be found the best 

means for effecting it. Compared with chemical precipitation it has 

the advantage that its sludge is less in amount, besides the fact that 

the cost of chemicals is saved. Experiments at Oldham (B. S. C., 

1902 b) pointed clearly to the superiority of the treatment without 

chemicals, and at Birmingham the substitution of septic tanks for 

precipitation resulted in a saving of $20,000 per annum and a decrease 

of 25 per cent in sludge (Watson, 1903). Whether any preliminary 

removal of solids is always desirable before final aerobic treatment 

is believed to be by no means certain. English authorities strongly 

tend to the opinion that such treatment is necessary. Rideal (190.1) 

holds that an anaerobic stage is necessary in the process of sewage 

purification, although he admits that it may be accomplished in long 

sewers without special treatment. Ward and Woodhead maintain
SEWAGE PURIFICATION BY CONTACT PROCESS. 53

that the destruction of cellulose in particular can be accomplished 

only under anaerobic conditions (R. S. C., 1902 L). Scott-Moncrieff, 

Whittaker, Stoddard, and Fowler (Martin, 1905) all hold the process 

to be necessary. The practical data on which these conclusions 

are chiefly founded are discussed on pages 63-64. These data are in 

general the results of experiments at Leeds, Manchester, and other 

cities which showed that aerobic niters of large material, worked as 

contact beds, tended to clog badly when treated with crude sewage, 

while they worked well if the sewage was previously septicized. Experiments on coarse niters through which sewage is allowed to trickle 

continuously have suggested, on the other hand, that crude sewage 

may sometimes be successfully treated at rapid rates and settled later 

after it has been nitrified. There are numerous examples in nature 

of the destruction of organic matter by purely aerobic processes. 

Even cellulose is most actively attacked just at the surface of the 

ground, as evidenced by the decay of fence posts. Dibdiii (1904), 

almost alone among the English sanitarians, has recently taken a 

strong position against the theory that the decomposition of cellulose 

must necessarily be anaerobic. The writers are of the opinion that 

the anaerobic process has not been shown to be a universally necessary step in the process of purification. In many plants it will no 

doubt prove usefuL In other cases, however, a short preliminary 

sedimentation without septic action or subsequent sedimentation of 

a trickling effluent obtained by the treatment of crude sewage may 

be more economical.

In the eastern part of the United States, where ample areas of 

sand of the right quality are available for intermittent filtration, 

the use of the septic tank is rarely held to be necessary. In most 

cases the solids are discharged directly on the surface, where they 

are partly oxidized and partly accumulate as sludge. In the Middle 

West, on the other hand, where sand areas are limited and rates 

must be high, the use of the septic tank is very general. Barbour, 

Alvord, and Shields are all strong advocates of the practice, and 

the plants they have installed work very satisfactorily at higher 

rates than those in use with raw sewage in Massachusetts. At Saratoga (Barbour, 1905) the rate is 0.1, at Lake Forest it is over 0.4, 

and at the Wauwatosa county institutions 0.4.

PURIFICATION OF SEWAGES BY THE CONTACT PROCESS IN BEDS OF

COARSE MATERIAL.

It has been shown that the scientific development of the process 

of purifying, sewage by the action of oxidizing bacteria really dates 

from the experiments conducted at Lawrence, Mass., under the 

direction of Hiram F. Mills. The direct application of the method 

of intermittent filtration is, however, rather narrowly limited by
54 THE PURIFICATION OF BOSTON SEWAGE.

local conditions. In many regions the cost of constructing sand 

filters of sufficient area to treat sewage at a rate of 0.1 million gallons per acre per day would be entirely prohibitive. For England, 

in particular, it was necessary to modify the process so as to obtain 

higher rates of filtration, even at the cost of a lower purification. 

This was first accomplished in a practically effective manner in a 

series of experiments carried out at Barking for the London county 

council, the attainment of a high rate being made possible by the 

use of materials coarser than sand. Almost insensibly this changed 

the whole conception of sewage purification. With coarse material 

there was little true "filtration," and it became evident that the 

bed was really not a filter, but an oxidizing machine. Frictional 

resistance could no longer be depended on to delay the flow through* 

the bed sufficiently to allow purification to occur. It was necessary, therefore, to regulate the rate by constructing water-tight filters, in which the .sewage could be retained in contact with the 

filling material and its accumulated growth of micro-organisms. 

Hence this type of purifying plant was called the "contact bed." 

It operated with success, attracted wide attention, and inspired the 

design of numerous so-called "biological filters" on similar principles. 

W. J. Dibdin, chemist to the London county council, was one of 

the first English sanitarians to grasp the essential principles of sewage purification. In studies of the self-purification of the Thames, 

H. C. Sorby had pointed out as early as 1883 the part played by 

living organisms, although he had in view chiefly the consumption 

of solids by the larger microscopic forms. In 1884 Dupre went a 

step further in affirming the relation of organic life to the oxidations which take place in a purifying stream. Didbin, who had 

been associated with both these observers, read a paper before the 

Institution of Civil Engineers in 1887, in which he worked out the 

whole theory as follows:

In all probability the true way of purifying sewage, \wfeere suitable land is unavailable, 

will be first to separate the sludge, and then to turn into the effluent a charge of the 

proper organism, whatever that may be, specially cultivated for the purpose, and retain 

it for a sufficient period, during which time it should be fully aerated and finally discharged 

into the stream in a really purified condition. This, indeed, is only what is aimed at 

and imperfectly accomplished on a sewage farm. [Dibdin, 1903.]

The treatment of London sewage by chemical precipitation alone 

was recognized by the metropolitan sewage commission in 1884 as 

only a temporary expedient, a final treatment on land being contemplated. As soon; therefore, as the Massachusetts results were 

published Dibdin saw their importance and began a series of investigations on the treatment of sewage on the Lawrence principle, but 

at more rapid rates. His first series of investigations was carried 

on between May and August, 1892, to determine the best material
SEWAGE PURIFICATION BY CONTACT PROCESS. 55

to employ. Four wooden tanks were installed at the northern 

(Barking) outfall. Each was 5 feet deep and had an area of one 

two-hundredth of an acre, and they were filled, respectively, with 

burnt clay, pea ballast (Lowestoft shingle), coke breeze, and a combination of gravel and sand over a layer of proprietary material. 

All received effluent from the chemical precipitation tanks at an 

average rate of 0.4 million gallons per acre per day. Sewage was 

allowed to 'run through continuously for eight hours, the rate being 

controlled by partially closing the outlet valves, and the beds 

were allowed to stand empty for aeration during the remainder of 

the twenty-four hours. The coke breeze, as indicated in Table XX, 

proved most satisfactory, the coarser burnt clay yielding a much 

poorer effluent, and the sand clogging seriously and giving a clear 

but imperfectly purified filtrate.

TABLE XX. Results of filtration through various coarse materials, London experiments, first 

series, May to August, 1892 (Clowes and Houston, 1904}.

[Parts per million.]

Effluent from filter No.

Effluent from filter No.

Effluent from filter No.

Effluent from filter No.

Oxygen consumed in 

4 hours at 

80° F., 

filtered.

20.1

11.6

9

7.2

Albuminoid 

nitrogen.

2.7

1.3

1.3

1.1

.8

Coke breeze was fixed on as the best material for further experiments, and a second series was begun to study the details of practical operation on a larger scale. A filter bed 1 acre in area, consisting of 3 feet of pan breeze covered with 3 inches of gravel, was 

constructed at Barking and put into operation in September, 1893. 

At first the bed was dosed too heavily and soon became clogged and 

foul. The need for rest and aeration, especially when a new filter 

is first operated, was thus clearly shown. After three months' rest 

the bed could handle two fillings a day, the sewage being allowed 

to stand in it for a period of from one to two hours. The cycle 

finally established allowed one and one-half hours for filling the 

bed, two hours for standing full, two and one-half hours for emptying, and six hours for aeration. When gradually worked up to its 

full capacity sewage could be treated at a rate of 1.2 million gallons 

per acre per day; the purification effected by the filter, suffered no 

reduction with age; and the analytical results were excellent, as 

indicated in Table XXI. .
56 THE PURIFICATION OF BOSTOtf SEWAGE.

TABLE XXI. Results of contact treatment at London, acre filter (Glowes and Houston, 1904)

[Parts per million.]

Period.

September-December, 1893 . . . 

April-June, 1894. .............

May-June, 1897. ..............

1900-1901......................

Oxygen consumed in 

4 hours at 80° F.

Chemical 

effluent.

59 

59 

52 

61 

46 

31 

55

Filter effluent.

17 

12 

10 

14 

9 

6 

9

Nitrogen as 

Free ammonia.

Chemical 

effluent.

4.8 

4.9 

4.7 

4.8 

4 

3

Filter effluent.

1.4 

1.1 

1.3 

1.4 

1.3 

.9

Nitrates.

Chemical 

effluent.

1.6 

1.8 

.3 

5.4 

2 

.6 

.4

Filter effluent.

1.9 

3.4 

2 

9.7 

7.6 

4.1 

10

The early London experiments of Dibdin have been greatly extended 

since 1898 by Clowes and Houston. Various details of construction and 

operation were worked out at both the Barking and Crossness outfalls, and the recommendation was finally made that the present plan 

of chemical treatment be abandoned and that the London sewage be, 

first, settled to remove gross mineral matter; second, septicized for 

six hours; and, third, treated in single contact beds of coke, 12 feet 

deep, at a rate of 5.2, attained by four fillings per day (Clowes and 

Houston, 1904).

In 1894, as a result of the first Barking experiments, Dibdin installed seven experimental contact beds at Button, in Surrey. Here 

two important modifications of the contact system were introduced. 

In the first place, the sewage was subjected to successive treatments, first in coarse and then in finer-grained beds the " double 

contact" system. In the second place, after the process had worked 

well with chemical effluent, as it had done at London, the treatment 

of crude sewage was attempted. Beginning November, 1896, a 

double-contact system treating crude sewage was operated for the 

first time. The depth of the beds was 3 feet 6 inches, and the filling 

material burnt ballast, larger than three-eighths inch. Two fillings 

a day were made, giving a rate on each individual bed of 0.9. The 

analytical results showed a reduction of oxygen consumed from 76 

parts per million in the sewage to 26 parts in the effluent of the first 

bed and 10 parts in the effluent of the second bed (Dibdin, 1903). 

The system worked for five years with admirable results. At present sewage is carefully screened (2 to 3 tons of solids per million gallons being removed) and then treated in primary coarse beds of burnt 

ballast and secondary fine beds of coke breeze, at a combined rate 

(based on the area of both sets of beds) of 0.36. It is calculated that 

the cost of operation is only about $20 per million gallons, as against 

$75 for the original treatment with iron sulphate and lime (Rideal, 

1901).
SEWAGE PURIFICATION sr CONTACT PROCESS. 57

The general principles of the contact system being thus established, 

it becomes necessary to work out details of construction. , One of the 

first of these details concerns the nature of the filling material. In 

the Sutton tanks it was found that burnt clay gave somewhat better 

results than the other substances, although it tended to break down 

badly. Granite and slate proved more permanent (Thudichum, 1903)'. 

The important series of experiments carried out at Barking and Crossness in 1898-1901 showed that for treating London sewage coke was 

preferable to stone, as indicated in Table XXII.

TABLE XXII. Results of contact treatment at London (Barking), 1898-1901 (Clowes and 

Houston, 1904)- Analyses of effluents.

[Parts per million.]

Period and treatment.

September, 1898, to April, 1899:

July 4-15, 1899; Sept. 21, 1899, to May 19, 1900:

Double contact, coarse and fine coke, 10 feet 

Nov. 7, 1900, to Aug. 10, 1901 :

Septic tank B ...............................

Suspended 

solids.

661 

73 

31

" 667 

177 

100 

139 

32

Oxygen consumed - 

in 4 hours at 80° F.

Total.

145 

32 

24

124 

38 

23

129 

84 

51 

82 

37

Dissolved.

54 

28 

20

63 

23 

18

68 

54 

33 

53 

76

Nitrogen as 

Nitrites.

0.2 

1.6

.7

.2 

1.2 

.6

.1 

.0 

.4 

.0 

.6

Nitrates.

1.3 

21.7 

12.5

1.1 

10.2 

21.8

.4 

1.7 

7.5 

1.3 

12.9

Dibdin and Thudichum report a series of studies summarized in 

Table XXIII which again indicate the superiority of coke.

TABLE XXIII. Comparison of filtering material (mean values) (R. S. C., 1902 a). Analyses

of effluents.

[Parts per million.]

Material.

Coke ...........................................................

Coal......................... .................................

Nitrogen as 

Free 

ammonia.

16.6 

23.4 

23.8

Albuminoid 

ammonia.

0.58 

1.04 

.12

Oxygen consumed in 

4 hours at 

80° F.

0.94 

1.52 

1.55

At Lawrence, also, by far the best results have been given by coke. 

Rough materials give better qualitative results than smooth materials. Broken-stone filters have not been particularly efficient (Massachusetts, 1903). The general results obtained at Lawrence on single-contact nitration are shown in Table XXIV.
58 THE PUEIFICATIOJST OF BOSTON SEWAGE.

TABLE XXIV. Results of single-contact treatment at Lawrence, Mass. (Fuller, 1905).

 No. of filter.

103.............

107.............

135..-....--....

154:............

167.............

176.............

Material.

J- to 1-inch coke.

\- to 1-inch stone 

Coke, breeze. ... 

Stone (walnut) . 

J- to 1-inch doke.

(inches). Depth 

60 

24 

214 

48 

48 

60

Preliminary 

treatment.

Septic . . 

None . . . 

None . . . 

Septic . . 

Septic . . 

None . . .

a 

hS3 S3 wro

fife i?£3 ^ 

o> 3«

0.6 

.55 

1.2 

.5 

.3 

.7

Analyses (parts per million)

Sewage.

Nitrogen 

as 

i

ijoj S

38.7 

23.8 

37.8 

58.7 

85.3 

37.2

"2 

*O S3

11Is «!*

3.3 

4.6 

5.6 

6.6 

8.5 

6.1

 8 

§o

SM !>> 

M

0

27.3 

34.5 

49.5 

45.4 

65.9 

42.8

Effluent.

Nitrogen as 

6

$* S'S

o> -M 

PH

7.9 

13.4 

20.3 

42.3 

54.6 

13.1

 V . '2-3

fl a '3 o

Is Is<*

0.9 

1.7 

1.7 

2.2 

3.2 

1.5

«

1 

S

21.2 

5.4 

3.4 

3.0 

13.4 

11.3

 8 

1o

!>} M

O

7.8 

15.7 

13.3 

14.9 

20.9 

7.7

At Birmingham it was found that the purification, measured by 

reduction in oxygen consumed, was 64 per cent with broken stone, 71 

per cent with slag, and 93 per cent with coal (Brejitschneider and 

Thumm, 1904). There is some evidence (see p. 82) that coal exerts 

a specially favorable action in trickling filtration (Hill, 1897). At 

Manchester (1901) materials containing iron were found to yield particularly good results. At Hamburg it appeared that the amount of 

porosity is immaterial and that the chief desideratum is iron content. 

Thumm, by the addition of 1 per cent iron to gravel or pumice, increased the purification in two contact beds from 46 and 42 to 66 and 

62 percent, respectively (Thumm, 1902).

A series of experiments on various materials conducted by Zahn at 

Charlottenburg in 1901 showed that brick gave iJhe best results, followed by slag, coal, coke, and gravel in the order named. The results 

are brought together in Table XXV. In each case the secondary sand 

filter was operated as a contact bed, the sewage standing on it under 

a head during the full period. It acted chiefly as a strainer to remove 

suspended solids.

TABLE XXV. Results of Charlottenburg experiments on contact filtration (Zahn, J903).

[Parts per million.]

-1 ' \b. Sand...........

11 tb. Sand. ..........

-111 ' \b. Sand...........

1V - \b. Sand...........

Total solids.

Total.

1,121 

1,059 

1,068 

1,028 

1,044 

1,084 

1,137 

1,229 

1,280

Loss 

on ignition.

294 

163 

149 

159 

177 

203 

235 

173 

204

Suspended solids.

Total.

413 

82 

0 

38 

0 

101 

0 

39 

0

Loss on 

ignition.

272 

54 

0 

22 

0 

68 

0 

20 

0

Nitrogen as 

Free ammonia.

65 

22 

17 

36 

24 

32 

20 

21 

18

Albuminoid ammonia.

19 

11

7 

9 

7 

12 

6 

8 

8

Nitrates.

0 

Present... 

.....do....

.....do....

.....do.... 

.....do....

.....do....

.....do....

.....do....

Oxygen 

consumed 

in 10 

minutes' 

boiling.

118 

64 

50 

66 

50 

82 

52 

58 

43
SEWAGE PURIFICATION BY CONTACT PROCESS. 59

In general, these results with regard to kind of material are somewhat inconclusive. Coke and coal seem particularly favorable and 

the presence of iron is apparently important. Cameron and Harding 

consider smoothness of surface desirable (R. S. C., 1902 a), but this 

conclusion is scarcely borne out by the successful use of coke.

The nature of the material used will necessarily depend much on 

local conditions. Its size is more a matter of choice and this factor 

is of even greater practical importance. Reference to the Hamburg 

results in Table XXVIII illustrates this point. It will be noticed that 

one-eighth to five-sixteenths inch material in experiments B and C 

gave twice as much purification as three-eighths to 1J inch material 

in experiments L, M, N, and P. The high purification in these 

beds was, however, accompanied by great loss of capacity. At the 

royal testing station at Berlin, it was found in experiments with 

several different sewages that one-third to 1 inch slag for the first contact and one-eighth to one-third inch slag for the second contact gave 

the best results. The primary beds effected'a purification of 20 to 30 

per cent. The secondary beds raised this figure to 70 per cent and 

produced a nonputrefactive effluent (Thumm, 1902). Clowes and 

Houston (1904), as a result of their London experiments, recommended the use of "walnut-size coke." ' In evidence before the royal 

sewage commission, Fowler recommended one-eighth inch material, 

Cameron one-eighth to one-half inch, Fraiikland one-eighth to threefourths inch, and Dibdin one-half to 4 inch for first contact and onesixteenth to three-eighths inch for second contact (Martin, 1905). 

Barwise (1904) suggests the use of coarser filling 3 to 5 inch material 

for primary beds and one-half to 1J for secondary beds to treat septic 

effluent. An interesting suggestion has recently been made by Dibdin 

(1904), who recommends the construction of "multiple-surface bacteria beds" of tiers of slate or brick regularly built up so as to secure a 

liquid capacity sometimes reaching 80 per cent. A bed built at 

Devizes on this plan is said to have cost less than one-third as much as 

an ordinary coke bed. Analyses from such a bed are shown in Table 

XXVI.

TABLE XXVI. Results from "midiiple-surface bacteria bed, February 9 to March 35, 1904

(Dibdin, 1904).

Average number of fillings per day........................................... 0. 83

Nitrogen as albuminoid ammonia:

In sewage...........................................parts per million.. 9. 9

In effluent.....................................................do.... «1.8

Oxygen consumed in 4 hours at 80° F.:

In sewage ...................................................... do.... 76. 6

In effluent.....................................................do.... 58. 7

If a bed were filled with perfect spheres of uniform size its open 

space or water capacity would be 26 per cent of its original cubic 

capacity. In beds built of the ordinary materials actually used this
60 THE PtJKIFICATIOF OF BOSTON SEWAGE.

value varies from 30 to 50 per cent. With progressive use the capacity 

decreases, and this is one of the most serious problems in the operation 

of the contact bed.

In an admirable analysis of the causes which affect the loss of 

capacity in contact beds the Manchester experts (Manchester, 1902) 

arrange them under the following five heads:

(a) Settling together of the material.

(5) Growth of organisms.

(c) Impaired drainage.

(d) Insoluble matter entering the bed.

(e) Breaking down of the material.

The first cause must always operate to a considerable extent and in 

part accounts for the great initial loss when the bed is first put in 

operation. If the original liquid capacity is determined, not by 

filling with water and measuring the effluent, as should be done, but 

by measuring the amount of water or sewage required to fill it, the 

initial loss will appear much larger than it really is, by the amount of 

water required to saturate the surfaces and pores of the dry material. 

The relative importance of this initial loss and of the true loss due to 

settling, growth, etc., is indicated in Table XXVII.

TABLE XXVII. True and apparent loss of capacity in a contact bed (Martin, 1906).

First filling, Aug. 15,1896.. ......... .. . ..... .. ... ....................

Filling Aug. 21, 1896 ................................................................

Filling Nov. 14-15, 1896. ............................................................

Capacity.

Gallons.

23,431 

13,775 

10,302 

7,893

Per cent 

of total.

100 

59 

44 

34

The actual decrease in capacity after the first filling is partly due, 

as noted above, to the breaking down of uniform materials into pieces 

of more varied size which become more closely packed together. Theamount of this loss may be measured by the space left by the settling 

over the top of the material. At Pawtucket it was estimated that 

about one-third of the total capacity loss in eighteen months was due 

to this factor. Such loss may be avoided to a great extent, as has 

been pointed out above, by the use of compact and permanent filling. 

This was shown very clearly in the Hamburg experiments. Table 

XXVIII shows, by a comparison of experiment G with H and I and of 

experiment N with M and O, that slag, while giving as good analytical 

results as coke and gravel, showed appreciably less loss of capacity.
SEWAGE PURIFICATION BY CONTACT PROCESS. 61

TABLE XXVIII. Statistics of Hamburg experiments on contact filtration (Dunbar and

Thumm, 1902).

No. of experiment.

B...... 

C......

L......

D......

E......

F......

G...... 

H......

I...... 

K......

M......

N......

0...... 

P......

Material.

Kind.

Slag...... 

.....do....

Coke. .....

Slag. 

Gravel. . . .

Coke......

Slas?.--... 

Coke......

Gravel. . . .

Gravel + 

1 per 

cent 

iron 

turnings. 

Coke......

Slag. 

Gravel. . . .

Size 

(inches) .

I to A

4 tO Jg

1 to 1J

i to T"g 

1 to fg

t to A

A to I

3 +n 3

4 tof 

A to f

I toll 

I to H 

ItolJ 

itolj

Kind of sewage 

received.

.....do...........:...

.....do...............

Effluent from L .....

.....do..............

.....do............... 

Effluent from N ..... 

.....do...............

Effluent from M (4 

months} and P (7 

months) . 

Effluent from M .....

.....do...............

.....do...............

.....do...............

Number of 

fillings 

per 

day.

1 

2 

6

3 

2

2 

3 

3 

3

.3

3 to 6 

3 to 6 

3 

3

Length of run(months) .

26 

14 

15

15 

11

15 

11 

11 

11

n

12 

12 

12 

12

Oxygen 

consumed 

in 10 minutes' boiling.

Sewage.

96 

91 

80

80 

80

80 

90 

90 

90

90

88 

88 

88 

88

Effluent.

27 

21 

52

20 

19

19 

30

27 

28

29

63 

65 

46 

46

Capacity 

(parts per 

million) .

Original.

33 

41 

38

43

27

36 

39 

39 

31

31

44 

48 

35 

44

Final

20 

15 

' "30

17 

14

22 

23 

22 

19

]9

38 

39 

26

28

Remarks.

Washed 

twice.

Washed 

once.

 Fell to 18 per cent before last washing;. ^

In England the loss of capacity due to breaking down of material 

has been found to be serious with clay not thoroughly burnt, and the 

need for permanent filling has led to an extensive use of various sorts 

of furnace clinker. Many English beds are, however, still built of 

friable stuff. Baker (1904) says: "It seems strange to an American 

to see so much perishable material used for filter beds," and suggests 

that in the United States gravel or broken stone will probably be 

preferable to cinders, clinker, or brick.

The capacity loss due to impaired drainage, like that from the 

breaking down of material, may be controlled to some extent by 

proper construction of the beds. The other two losses, due to growths 

and to deposition of solids, are more or less inevitable.

The loss of capacity due to the growth of organisms is more or less 

directly correlated with an increasing purifying power of the bed. At 

Manchester it was found that "the chemical efficiency is increased' 

by a loss of capacity. These beds purified four doses after they had 

become partly clogged as readily as three when clean. The amounts 

were about the same in the two cases." (Manchester, 1899.) Dunbar gives the figures quoted in Table XXIX to illustrate this point. 

He considers that the ability of the filter to absorb rapidly free 

ammonia from the sewage is an index of the amount of growth within 

the filter.
62 THE PURIFICATION OF BOSTON SEWAGE.

TABLE XXIX. Improvement in ammonia absorption in a contact filter {Dunbar and Thumm,

1902).

Months at

work.

1

2

5

8

10

14

Loss in ammorra (per

Single

filling.

9.1

34.6

35.2

47.4

43

 40.5

Double

filling.

14.6

30.9

23

41.3

41.2

41 6

This sort of loss due to growth is almost independent of the character of the liquid filtered. Dunbar treated coke contact filters with 

various substances (134 fillings in four months) and found with tap 

water a reduction in capacity from 48 to 40 per cent; with tap water 

plus 1 per cent urine, from 47 to 37 per cent; with unfiltered sewage 

from 48 to 37 per cent; with filtered sewage, from 48 to 40 per cent, 

and with sewage precipitated with lime, from 44 to 36 per cent (Dunbar and Thumrn, 1902).

The loss of capacity due to the deposition of the insoluble mineral 

matter which enters the beds is also serious and in England has necessitated' the complete renewal of many contact filters.- It may be 

avoided to a considerable extent by preliminary straining and sedimentation, and it" tends to be concentrated in the upper layers of the 

filter. With some sewages, however, it seems clear that contact filters 

will require frequent renewal. The experiments at Leeds furnish a 

good example of this. Table XXX indicates a reduction to values as 

low as 9 and 11 per cent. It appeared evident to the experts in this 

case that in order to treat Leeds sewage in contact beds it was necessary to use an even, hard filling material, >to remove suspended mineral 

matter by careful sedimentation, and to exclude iron compounds from 

the sewers. Even then they considered the permanency of the beds 

more than doubtful.

TABLE XXX. Loss of capacity in contact beds at Leeds raw and settled sewaae (Leeds,

1905).

No. of 

bed.

1.......

3.......

5.......

8.......

Material. Period.

Ofit. 2, 1897, to Oct. 7, 1899. . .........

Nov. 19, 1898, to Jan. 10, 1901......

Mar. 8, 1899, to Feb. 15, 1001 ..........

Original 

capacity 

(per cent) .

48

51

52

31

01

Final 

capacity 

(per cent) .

15

14

11

9

12

It is possible to restore the original capacity of contact beds to a 

considerable extent by allowing them to rest empty for several weeks 

Table XXXI shows how efficient this process was at York and at 

Leeds in the case of two of the beds above referred to. - Rest can of
SEWAGE PUKIFTCATION BY CONTACT PKOCESS. 63

course effect only the disintegration of the organic growth and can not 

affect the accumulated mineral matter. The restoration of capacity 

can therefore never be complete.

TABLE XXXI. Loss in capacity of contact beds and. its recovery by resting. 

NABURN DISPOSAL WORKS, YORK (YORK,. 1901).

Bed No. 1.

U.S. 

gallons.

55,200

22,300

11,200

16,400

11,500

Per cent 

open space.

100

40

20

30

21

KNOSTROP SEWAGE WORKS, LEEDS (LEEDS, 1900).

Bed No. 7, single contact.

Bed No. S, eingle contact.

222,000

66,800

25,900

64,200

30,700

113,000

35,400

12,800

32,300

11,800

100

31

12

30

100

31

28

10

The treatment of septic effluent instead of crude sewage greatly prolongs the life of the contact bed. In the Barking experiments (Clowes 

and Houston, 1904) the capacity of two primary coke beds fell in ten 

months from 69 and 70 per cent to 20 and 18 per cent, respectively. 

Secondary beds showed only a reduction from 62 to 51 per" cent 

(coarse) and from 53 to 44 per cent (fine). The stone beds lost about 

1 per cent of their original liquid capacity per week. A series of experiments with septic effluent followed, in which after the first loss a 

capacity of about 30 per cent was constantly maintained. At Leeds 

it was found that beds taking septic effluent showed much higher 

capacities than those which received crude sewage. Similar conclusions were drawn by .the experts at Manchester, although the experiments made with crude sewage were not exhaustive. The capacity 

of beds treating septic effluent decreased during the first three months 

and then remained fairly constant at about 33 per cent (of the original 

cubic contents), as shown in fig. 6. At Burnley, with septic effluent, 

the capacity of contact beds fell from 44 to 19 per cent; at Exeter it 

fell from 39 to 28 per cent, and at Leicester from 49 to 29 per cent. 

At Sutton a minimum of 21 per cent was reached (R. S. C., 1902 a). 

At Oldham "no clogging" was reported after two years (Oldham, 

1901). In still other places even crude sewage has been treated with 

success. At West Bromwich the capacity of primary beds fell from 33 

to 19 per cent and of secondary beds from 33 to 24 per cent in some-
64 THE PUBLICATION OF BOSTON SEWAGE.

thing over a year. At Newbury the capacity of single-contact beds 

of clinker fell from 19,000 to 10,000 gallons, and that of gravel beds 

from 19,000 to 9,000 gallons in a year's operation. At Hampton it is

1

\

s

~7

\

\\

claimed that coarse beds after more than two years maintain "their 

original liquid capacity." At Maidstone and Wellington (Somerset) 

absence of sludge deposits in the beds was reported (R. S. C., 1902 b).
SEWAGE PURIFICATION BY CONTACT PROCESS. 65

Experiments in Germany have shown less favorable results as to, 

clogging, perhaps from the use of rather fine material and the treatment of very strong sewages. Dunbar's figures, as given in Table 

XXVIII, indicate final capacities of only 15 to 20 per cent with material ranging down to one-eighth and three-sixteenths inch. Experiments M, N, O, and P, with three-eighths to 1J inch material, show 

results substantially like those obtained in England. German practice, however, tends to single contact in beds of fine material. Under 

such conditions it appeared at Hamburg that the loss in capacity 

went on in a pretty regular ratio to the amount of applied sewage, the 

beds soon being so clogged that their capacity fell to 15 or 20.per cent. 

The average reduction with different materials is shown in Table 

XXXII. Capacities were not satisfactorily restored by periods of 

rest.

TABLE XXXII. Reduction in capacity of Hamburg filters (Dunbar and TJiumm, 1902}.

Material.

Single contact.

Loss in capac.ty (gallons per 

m 11. on gallons filtered) .

f 1,330

\ 1,680 

340

280

170

440

Material.

Second contact. 

Slag, g- to j5B-inch ....................

Gravel, J- to TV'nch.... ..............

Slag, f- to li-inch ....................

Loss in capac ty (gallons per 

m Hi on gallons filtered).

420

700 

630

340

360

460

650

The German investigators accept this serious clogging with equanimity and suggest the removal and washing of the material when 

the capacity falls to 20 to 25 per cent. This would be required two 

or three times a year (Dunbar and Thumm, 1902). The Prussian 

commission at Berlin came to similar conclusions (Bruch, 1899). 

Material showed in these experiments a considerably greater capacity 

after washing than when it was first used. It seems probable that 

the use of coarser materials, which under proper conditions do not 

require so frequent removal, is a more economical process. Some of 

the English filters, for example, have been operated for six years with 

fair success (Martin, 1905).

Next to the nature and size of filling material the depth of the 

contact bed is the most important point of general theoretical interest in its construction. Exhaustive experiments were carried out on 

this point by Clowes and Houston (1904) at London, from which it 

appeared that beds 3 feet, 5 feet, and 13 feet in depth gave equally 

good effluents. Studies at Exeter, in which samples were taken from 

IKB. 185 06 5
66 THE PURIFICATION" OF BOSTON SEWAGE.

taps placed at different depths in a contact filter, showed the best 

results at 3 feet below the surface, and at Manchester a 15-inch 

bed gave specially good results. At Leeds, on the other hand, 

-6-foot beds proved better than those of half that depth (R. S. C., 

1902 a). Thumm (1902) considers 4£ to 6 feet a maximum depth for 

one-third to 1 inch material and 1^ to 3 feet a maximum for material under one-eighth inch.

With regard to the operation of contact beds, the number of fillings 

is the first point to be considered. At Hamburg it was found that for 

single contact two fillings a day gave the best results, while for double 

contact six fillings of the primary beds and three fillings of the secondary beds were recommended (Dunbar and Thumm, 1902). In the 

Barking experiments (Clowes and Houston, 1904) it was shown that 

two fillings a day gave better results than one; apparently a single 

filling does not maintain the bacteria at their maximum effectiveness. 

Birmingham experiments have indicated three fillings a day as effective, to be cut down to two if specially high purification is desired 

(Watson, 1903). At Crossness it was found that London sewage 

could be purified with as many as four fillings. At Manchester (1901) 

also four fillings were recommended.

The distribution of fillings at regular intervals over the twentyfour hours does not appear to be a necessity. At Manchester contact 

beds were operated for two months with four even six-hour cycles and 

then for three months with four cycles in ten hours, followed by fourteen hours' rest. The results, as shown in Table XXXIII, were better by the second method.

TABLE XXXIII. Results of operation of contact beds at Manchester, England (R. S. C.,

1902 &).

Mode of operation.

Analyses of effluent (parts per million).

Oxygen 

consumed 

in 4 hours 

at 80° F.

29 

22.3

Nitrogen asFree 

ammonia.

16.8 

14.8

Albuminoid 

ammonia.

1.5 

1.1

Nitrates.

2.6 

6.3

The duration of the full period may also vary. Dibdin adopted two 

hours, and this is perhaps the general English practice. In Germany, 

too, Schumburg and others advocate this period (Bruch, 1899). 

Harding at Leeds found that one hour gave inferior results, while four 

hours was no better than two (R. S. C., 1902 a). Roscoe and Cameron, on the other hand, advocate shortening the period to one hour 

(R. S. C., 1902 a). Frankland found that a value for oxygen consumed of 555 parts per million for raw sewage was reduced to 93 in
SEWAGE PURIFICATION BY CONTACT PEOCE88. 67

five minutes. It was still 93 after thirty minutes and 49 after twelve 

hours (Barwise, 1904).

The rate of filtration on contact beds, which is usually expressed 

in relation to the superficial area, is of course a function of the depth 

and the number of fillings. It would be more reasonable to measure 

contact rates in such units as acre-yards, which take account of 

depth. For uniformity with sand and trickling filters, however, the 

unit of superficial area is used in this paper. With a bed 3 feet deep 

and an open space of 33 per cent, which is a liberal estimate for a 

matured filter, two fillings a day would equal a rate of 0.65 million 

gallons per acre per day and three fillings a rate of about 1. In practice, necessary rests and loss of capacity being taken into account, 

three fillings of a 3-foot bed will not amount to a rate of more than 0.8. 

At Barking, in 1898, Clowes and Houston (1904) obtained with one 

filling rates of 0.6 for coke and 0.5 for ragstone, and in 1899 with two 

fillings the rates were increased only to 0.7. Watson (1903) considers 0.4 to 0.6 the best rate attainable, even when the sewage has 

been previously subjected to septic treatment. Table XXXIV, 

compiled from Watson's Birmingham lecture and from the testimony 

before the royal sewage commission, indicates the rates which have 

been recently obtained in actual operation or in experiment on a 

practical scale.

TABLE XXXIV. Contact-filter rates (Watson, 1903; Martin, 1905).

Single contact.

Place Depth 

(feet).

3.3

4.5 

3.7 

5 

3.5 

3 

4.5

Rate (million 

gallons per 

acre per day).

0.6 

.6

.8 

1 

1 

1.2 

1.4

Double contact.

Place.

Sheffield. ................

Depth 

(feet).

3 

5.5 

5.5 

3.3 

4 

3.3

Rate (million 

gallons per 

acre per day).

0.3 

.6 

.8 

.8 

1.1 

1.2

When a double-contact system is used the area must naturally be 

increased, generally by 50 per cent, the secondary beds being operated at double rate. The discussion of analytical results (pp. 70-71) 

shows'that single-" contact rarely yields a stable effluent, while double 

contact usually does. The fact that, with a given area, better results 

can be obtained by double treatment at a certain rate than by single 

treatment at half that rate is made clear by some Manchester experiments, the results of which are given in Table XXXV.
68 THE PURTFICATIOlSr OF BOSTOIST SEWAGE.

TABLE XXXV. Results of double and single contact treatment at Manchester, England

(Manchester, 1904 «) 

[Parts per million.]

Free 

ammonia.

25.8

14.5

4.1

31

13.3

Nitrogen asAlbuminoid 

ammonia.

2.5

1.2

.5

3.5

1.3

Nitrates 

and 

nitrites.

0.5

8.5

4.3

Oxygen

consumed 

in 4 hours 

at 80° F.

70

22

6.9

80

16

In the Hamburg experiments it was found that with six daily fillings in the primary bed and three in the secondary bed as good results 

were obtained by double contact as with two fillings in single-contact

125-

RAW SEWAGE PRIMARY EFFLUENT SECONDARY EFFLUENT 

FIG. 7. Comparison of sewages and effluents from contact beds.

beds. This is shown in Table XXVIII (p. 61), where experiment C 

and experiments L and D represent comparable conditions (Dunbar 

and Thumm, 1902). It may be noted in passing that in England general practice reverses this relation between primary and secondary 

beds. The Manchester commission suggested that secondary beds'
SEWAGE PURIFICATION BY CONTACT PEOCES8. 69

should be operated at twice the rate of the primary beds (Manchester, 1900 a).

The purification effected by single and double contact filtration is 

fairly represented by the analyses, collected from various sources, 

given for comparison in Table XXXVI. The removal of oxygen 

consumed at the two stages in the process is plotted in fig. 7. It will 

be noted that the first contact removes somewhat more than half of 

the organic constituents of the sewage, as measured by oxygen consumed and albuminoid ammonia, and two-thirds or more of the suspended solids, while the second contact effects almost as great a purification on the first-contact effluent. Aylesbury and Blackburn 

showed the worst results among the English plants as far as ratio 

'of purification is concerned. It will be noticed that these are the 

weakest sewages and in all sewage treatment the last fractions of 

organic matter are the most difficult to remove. Except at Lawrence the nitrate content of the effluent is rather low, notably at 

Leeds and Leicester.
TABLE XXXVI. Results of single- and double-contac

[Parts per million.]

Lawrence: 6 

Nos. 137-163 ........

Nos. 137-164........

Leeds: «

Manchester: g

Beds C and D ......

Solids.

Total.

Sewage.

1,190 

1,080

1,670 

1,690 

1,780 

1,320

1,630

First 

contact.

1,020 

602

1,080 

1,180 

1,170 

1,070

895

Second 

contact.

920 

596

980 

1,050 

1,020 

1,020

1,000

Suspended.

Sewage.

367

474

584 

614 

661 

296

824

First 

contact.

60

165 

180 

196 

73.2

45

Second 

contact.

0 

3

27 

47 

47 

23

5.6

Nitrog

Free ammonia.

Sewage.

36.3 

36.3 

56.4 

23.3

20.2 

23.8 

24.1

24 

24 

94.2

First 

contact.

24.3 

24.2 

42.7 

17.3

12.9 

10.8 

14.5

9.1 

8.5 

32.6

Second 

contact.

12 

8.6 

23.6 

11.4

3.7 

6.8

7.8

3.7 

3.6 

8.3

Albuminoid amm

Sewage.

5.9 

5.9 

6. 5

2.8

9.5 

11.3 

11.8 

10.6

 3.7 

3.7 

7.3

First 

contact.

2.4 

' 2.4 

4 

1.7

3.7 

3.4 

4.7 

4.2

1.4 

1.3 

2.9

a At Lawrence, 2 minutes' boiling.

& Lawrence: No. 137-163, run for 18 months during 1901-1902; area of beds, ^^ acre each; first contact, 

ary bed, fine coke, rate 0.7 (Fuller, 1905). No. 137-164, run for 6 months during 1901; like No. 137-163, except 

1905).

c Aylesbury: Experiments during first 6 months of 1898; weekly analyses; no further data given (R. S. C., 

<z Blackburn: No further data (R. S. C., 1902 a).

e Leeds: Nos. 1 and 2, experiments during October, 1898, to October, 1899; beds about J acre in area; prim

raw or settled sewage at rate of 0.8; secondary, 6 feet coke, A to 1J inches, rate like primary. Nos. 3 and 4, 

about J acre in area and 3 feet deep; primary bed filled with clinker J to 1 inch, and secondary TVto J inch; rate 

der of period 0.3 (raw sewage). Nos. 5 and 6, experiments during March to November, 1899; beds each J acre 

ary bed, 3 feet of clinker, -fa to J inch; rate, 0.8, raw sewage on each bed; 4 hours' contact during a portion of 

/Leicester: Process No. 14; experiments during November, 1898, to July, 1899; primary beds, ^5 acre in a

bed, A acre in area, filled with 3 feet of clinker, J to J inch; rate, 1.6 on each bed, septic sewage (Leicester, 1900)

^Manchester: Experiments during January 4, 1900, to March 27, 1901; A and C were primary beds, the co

 fr acre on the surface; slope inward, 2:1. A contains 3 feet of clinker J to f inch; septic sewage at rate of 0

rate of 0.4. D contains 3 feet of clinker J to J inch; rate, 0.7 (Manchester, 1901).

ft Button: Experiments from October, 1897, to August, 1898; coarse bed 3 feet deep, of burnt ballast; 5 bed
SEWAGE PURIFICATION BY CONTACT PROCESS. 71

To these results may be added one more set of analyses to show 

what contact beds have actually accomplished in practical operation 

on a large scale. At Manchester, in 1903, 28 half-acre primary beds 

had been installed. They were 40 inches deep and filled with oneeighth to 1 inch clinker and were dosed with septic effluent. The 

results of the first year of operation are shown in Table XXXVII.

TABLE XXXVII. Efficiency of primary-contact beds at Manchester, England (Bredtschneider

and Thumm, 1904).

Date.

1902.

Rate 

(million 

gallons 

per acre 

per 

day).

0.46

.54 

.56 

.56

Analyses (parts per million) .

Oxygen consumed _ 

in 4 hours at 80° F."

Septic Contact 

effluent, effluent.

i

85 I 34 

80 32 

89 32

Nitrogen as 

Free ammonia.

Septic 

effluent.

30 

29 

29

Contact 

effluent.

19 

17 

16

Albuminoid ammonia.

Septic 

effluent.

4 

3.2 

4

Contact 

effluent.

2.1 

1.7 

1.6

The effluent of the first contact process, as is obvious from the 

analyses in Table XXXVI, almost always retains too much organic 

matter to be considered satisfactorily purified. Two successive 

treatments, on the other hand, may produce an effluent which is 

nonputrescible and of good enough quality to be discharged into a 

stream. If still better results are desired a third contact may be 

made. Table XXXVIII shows what may be expected from such a 

method. The improvement in successive treatments progressively 

lessens, so that the results obtained are scarcely commensurate with 

the cost. The head required for successive contacts also introduces 

a serious factor.

TABLE XXXVIII. Results of triple-contact treatment. 

[Parts per million.]

Eastry (R. S. C.,1902b).

Bed 1 .............................

Bed2. ............................

Bed3. ............................

Leeds (Leeds, 1900) .

Bedl...... .......................

Bed 2.............................

Bed3.............................

Solids.

Total.

1,550 

1,460 

1,340 

1,360

1,760 

1,250 

1,060 

1,030

Suspended.

1,070 

107 

85.5 

21.4

632 

274 

113 

110

Nitrogen as 

Free 

ammonia.

25.5 

22 

12.4 

4.8

27.6 

18.6 

13.5 

9.7

Albuminoid ammonia.

12.8 

3 

2.4 

1.2

12.4 

7.1 

5.1 

3.5

Nitrates.

4.6 

1.9 

2.1 

7.4

2

Oxygen 

consumed , 

in 4 hours 

at 80° F.

123 

50.5 

25.4 

17.2

127 

62.4 

39.6 

27.5

It has been shown that the contact bed was developed from the 

intermittent sand filter with no idea of changing any other condition
72 THE PUEIFICATION OF BOSTON SEWAGE.

than the rate of operation. It was assumed that the chemical changes 

were the same in each case. Many English discussions of the process 

are based on this assumption, and Clark states that at Lawrence the 

process of nitrification is considered an essential for good purification 

(Clark, 1903).

Dunbar and Thumm (1902), in a beautiful series of experiments 

at Hamburg, have shown, however, that the reactions in the contact 

filter, as a result of the alternate aerobic and anaerobic conditions, 

follow a peculiar and characteristic course. First, during the reduction phase the solids in the sewage settle on the surface of the filling 

material and the soluble constituents are to a large extent absorbed 

by the bacterial jelly with which the material is clothed. This latter 

phenomenon takes place in virtue of the general tendency exhibited 

by colloidal films to remove substances from contiguous solutions 

(Phelps and Farrell, 1905). Dibdin illustrates the removal of suspended matter by analogy with the adhesion of floating chips to 

larger bodies, and compares the adsorption of dissolved material to 

the removal of lead acetate by passage through a carbon filter (Dibdin, 1904). The real purification of the adsorbed material has been 

shown by Dunbar (1905) to be a bacterial process, although Bredtschneider (1905) attempts to maintain its purely mechanical character. During the oxidation phase of full aeration the bacteria set 

up the ordinary oxidation processes of the intermittent filter, which 

may be indicated by the following generalized formula:

Reaction 1. Nitrification:

(b)NA + 02 =N205)

At the end of this period considerable quantities of nitrates are 

present in the filling material of the contact bed, as shown by Dunbar 

and Thumm (1902). Experiments by Phelps and Farrell (1905) 

indicate that the amount of nitrates increases with the length of the 

period. When the bed is refilled for the next cycle the same action 

continues for a time. Soon, however, the supply of dissolved oxygen 

is consumed, active nitrification stops, and anaerobic putrefactions 

begin, causing hydrolytic splittings of the following type:

Reaction 2. Hydrolysis :

(R.N:R' + 2H2O=R.OH + HO.R'.NH2)

At this stage the contact filter has the liquefying properties of the 

septic tank. There is a bacterial reduction of the nitrates to nitrites, 

and a formation of partly reduced nitrogenous bodies, primary 

amines, etc. This leads to a decomposition of the nitrites present 

and the liberation of gaseous nitrogen according to the following 

formula :

Reaction 3. Denitrification :
SEWAGE PUBLICATION BY CONTACT PROCESS. 78

During the reducing phase the nitrates formed in the empty period 

are partly or wholly removed. . Much of the organic nitrogen originally present is lost as free nitrogen. Clark (1903) has pointed out 

that this loss amounts to from 38 to 50 per cent and Phelps and Farrell (1905) found a loss of from 35 to 50 per cent. The nitrates found 

in the final effluent give no true measure of the purification effected, 

since under ideal conditions the nitrates formed from half the nitrogen would be exactly used up in decomposing the other half. Dunbar and Thumm (1902) found that the highest purification frequently 

accompanied the lowest nitrate content in the effluent.

The process in the contact bed is evidently an extremely complex 

one, involving an alternation of anaerobic and aerobic processes. 

To those who, like most English authorities, believe that putrefaction 

is an integral part of all sewage purification, such a method must 

commend itself. Clark (1900) describes a suggestive experiment in 

which gravel filters were run at a rate of 0.5 with forced upward aeration. Comparing these filters with others operated on the contact 

plan, he finds that the latter operate for longer periods and at higher 

rates without clogging and produce better effluents. Nevertheless, 

in view of recent English work on open filters through which raw 

sewage is allowed to trickle continuously, and in the light of some of 

the writers' own experiments, it can not be conceded that the universal necessity for anaerobic treatment has been clearly proved. 

Even if the need for some such process be granted, its combination 

with aerobic action in the same filter must be regarded as of doubtful 

expediency. As Bideal says, "In methods involving a 'resting-full' 

and 'resting-empty period' there is alternate inversion of bacterial 

action between aerobes and anaerobes, with a disturbance of both." 

And again, "In ordinary bacteria beds these reactions are somewhat 

fortuitously reversed and confused, according to the periods of filling 

or rest, the fault being caused by mixing all the different bacteria in 

one or two large filters" (R. S. C., 1902 a). Chemically the decomposition of organic matter into free nitrogen which takes place in the 

contact bed seems quite ideal. Bacteriologically the combination 

of two diverse processes must be regarded as theoretically unsound.

Whatever may be thought of the principle of the process, its practical applicability under certain conditions has been thoroughly 

demonstrated. The results obtained with the famous 1-acre coke 

bed at Barking and with the double-contact system at Sutton have 

been amply confirmed. The Barking bed between 1894 and 1901, 

inclusive, purified 1,500 million gallons of sewage at an average rate 

of 0.5 for the whole period. The elaborate experiments at Manchester and Leeds showed that even strong industrial wastes could be 

treated on this principle. At Exeter, Yeovil, Barrhead, Oldham, 

and Burnley contact beds are being regularly operated with success.
74 THE PURIFICATION OF BOSTON SEWAGE.

That the double-contact process may yield effluents as good as those 

obtained from sewage farms in actual operation is indicated in Table 

XXXIX, which presents data obtained by two river conservancy 

boards in the examination of a number of plants. No distinction 

has been made as to methods of preliminary treatment. All the 

contact beds and most of the land areas receive septic or chemical 

effluent. The Mersey and Irwell standard is 1.4 parts per million of 

albuminoid ammonia and 14 parts of oxygen consumed. The Kibble 

standard is 1 part of albuminoid ammonia and 20 parts of oxygen 

consumed.

TABLE XXXIX. Comparison of contact treatment with irrigation and sand filtration, Mersey 

and Irwell and Ribble watersheds (B. S. C., 1902 6).

District.

Ribble.......................

Disposal on 

i Con tact beds ............................

Contact beds .............................

Number of samples.

Above 

standard.

8 

55 

16 

88

Below 

standard.

22 

178 

22 

207

Per cent 

of samples below 

standard.

73 

76 

58 

70

German investigations have similarly shown at Hamburg (Dunbar 

and Thumm, 1902), at Berlin (Bruch, 1899), at Stuttgart (Schury, 

1905), and elsewhere that a clear nonputrescible effluent may be 

obtained by the contact method.

Whether preliminary septic treatment is necessary before contact 

filtration must be decided by local conditions in the individual case. 

English opinion strongly inclines to the view that it is generally 

advisable. The consensus of evidence given before the royal sewage 

commission indicated that "crude sewage causes so serious a loss of 

capacity in contact beds as to require preliminary sedimentation and 

generally septic treatment as well" and that the use of the septic 

tank "greatly assists the life of the beds by preventing their becoming 

choked by the accumulation of mineral and indigestible fibrous matters" (Dibdin, 1903). The Leeds experiments certainly showed that 

the crude sewage of that city could not be treated successfully. At 

London, Birmingham, and Manchester the conclusion has been reached 

that septic treatment is desirable. It must be remembered that 

sludge is produced in the septic tank, the disposal of which must be 

balanced against the renewal of contact beds. The cleaning of contact beds is of course much more difficult than the emptying of a 

septic tank. On the other hand, the sludge produced in the beds is 

probably less in amount and of a less offensive character than that 

which accumulates in the tank. Furthermore, it has been suggested 

that septic treatment under certain conditions may interfere with the 

course of the later biological process. At Hamburg it was found that
SEWAGE PURIFICATION BY TRICKLING PROCESS. V5

while contact beds could handle six doses a day of raw sewage only 

two doses of septic effluent could be applied, a third dose producing a 

dark and malodorous effluent (Dunbar and Thumm, 1902). Chemical treatment also interfered with the process, as shown in Table XL.

TABLE XL. Results of contact treatment of crude sewage and chemical effluent (Dunbar and

Thumm, 1902).

Precipitant.

Oxygen consumed 

in 10 minutes' 

boiling (parts per 

million).

Applied 

liquid.

102 

69 

69

72

Contact 

effluent.

27 

51 

53 

19

PURIFICATION OF SEWAGES BY A CONTINUOUS TRICKLING PROCESS 

OVER COARSE MATERIAL.

At about the same time that the system of contact treatment was 

worked out the foundations were laid for the development of another 

method of purification by rapid filtration through coarse material 

under wholly aerobic conditions. In modern filters of this type the 

supply of oxygen is maintained and the flow slackened sufficiently to 

permit purification by applying the sewage in a fine, continuous spray, 

and the beds are termed sprinkling or trickling filters. The early 

Lawrence experiments on the filtration of sewage " through clean 

gravelstones larger than robins' eggs" (Mills, 1890) furnished the first 

suggestion of such a process. In 1892 Hazen started a filter of onefifth-inch material which received four doses of sewage a day and was 

artificially aerated. The rate was increased from 0.14 at the start to 

0.48. The surface clogged badly, but the effluent was good, showing 

30 parts per million of nitrates. In 1892 Lowcock, at Malvern, England, constructed a gravel filter with a sand layer on its surface and 

filtered chemical effluent at a rate of nearly 0.3 million gallons per 

acre per day, forcing air under pressure into the middle layer of the bed. 

A good effluent was obtained and the filter was operated for fifty-one 

days without rest (Lowcock, 1894). Similar filters were later constructed at Wolverhampton and at Tipton (Kldeal, 1901). At both 

places ordinary trickling filters have since been installed (R. S. C., 

1902 a). In the United States Waring was attempting at. the same 

time to use the principle of forced aeration. He obtained a patent on 

his process as early as 1891 and carried out a series of experiments at 

Newport in 1894 on "the mechanical straining out of all solid matters 

carried in- suspension in sewage and their subsequent destruction by 

forced aeration and the purification of the clarified sewage by bacterial
76 THE PUKIFICATION OF BOSTON SEWAGE.

oxidation of its dissolved organic matter in an artificially aerated 

filter." Straining through broken stone removed 40 per cent of the 

nitrogenous matter in the sewage, and it was concluded that "if the 

thick sludge is removed and the upper 6 inches of the filtering bed 

opened up by raking or plowing after the filter is drained an aeration 

period not exceeding five days is sufficient to quite restore the strainer 

to its original efficiency." Waring says further that "the sewage, 

instead of passing through the filter in a solid column, as in the former 

case, trickles down in a thin film over the surfaces of the particles of 

coke or other filtering material, while through the voids between the 

particles and in immediate contact with the trickling films of liquid a 

current of air is constantly rising, being introduced at the bottom of 

the tank by a blower." It is stated in the report of these experiments 

that the aerators removed " over 95 per cent of the organic nitrogen of 

a strainer effluent applied at a rate of at least 800,000 gallons per acre 

per day" (Waring, 1895).

Waring's principle of oxidation was undoubtedly.correct; but the 

method of forced aeration is of more doubtful expediency. For the 

complete oxidation of various organic compounds Dibdin (1903) calculates that an amount of oxygen equal to from two to four times the 

weight of their total carbon would be required. This means with an 

average sewage a supply of 5 to 10 liters of air to a liter of sewage. 

The difficulty of maintaining such a supply of air by forced aeration is 

manifest, and the plants actually installed on the Waring plan have 

not generally operated with marked success. The best example of the 

process is that at East Cleveland. Here the beds speedily clogged 

when treating raw sewage, although since the installation of a septic 

tank for preliminary treatment they have worked better. The engineer of the Ohio State board of health says of this plant: "When visited 

in winter the surfaces of the aerators were frozen and they were out of 

service, the sewage being passed through septic tanks and primary and 

secondary filters only. It is said to be practically impossible to clean 

the surface of the aerators during cold weather, but on account of the 

rapid rate of filtration these filters rapidly accumulate solid matter on 

their surfaces and need frequent cleaning" (Pratt, 1905).

A practically successful solution of the problem of aeration has 

been reached along another line, and depends on the supply of sewage, continuously or at very frequent intervals, in small amounts 

distributed evenly over the whole area of a filter. Under such conditions the sewage trickles in thin films over the surface of the filling material, while the spaces between are continually filled with 

air, the oxygen content of which in practice does not become seriously exhausted (R. S. C., 1902 a). The air supply under the best 

conditions may amount to five times the volume of sewage. The 

material over which films of sewage continuously trickle supports an
SEWAGE PURIFICATION BY TRICKLING PROCESS. 77

active growth of micro-organisms. The condition is analogous^ the 

cultivation of acetic-acid bacteria in the process of vinegar manufacture by the flow of alcoholic liquor over shavings. The complications introduced by "a series of compensating errors of surfeiting 

and starvation" are exchanged for a simple and constant condition. 

Under the name of the trickling filter, the percolating filter, the 

"intermittent continuous" filter, the sprinkling filter, etc., this process has come nearer than any other to realizing the ideal conditions 

for rapid purification.

The first description of a method for sewage treatment based on 

the plan of trickling over coarse material with natural aeration was 

published by Stoddart in 1893. In the next year the same investigator exhibited a model at the Bristol meeting of the British Medical Association in which sewage and other liquids were discharged 

in drops over a filter of coarse chalk. A solution of ammonium 

sulphate containing, 140 parts per million of nitrogen was almost 

perfectly nitrified at a rate of 11.6 million gallons per acre per day. 

Sewage was completely nitrified at a rate of 1.2 and well purified 

at 5.8 (Dibdin, 1903). Nitrification was found to increase with the 

depth of the filter. The first working filter actually constructed by 

Stoddart was installed at Horfield in 1899. Its efficiency under various conditions of flow is indicated in Table XLI.

TABLE XLI. Results of purification by Stoddart trickling filter at Horjield, England (R. S. .,

1902 a).

Conditions.

Exceptionally strong 

sewage.

Dry-weather flow ......

Rate 

(million 

gallons 

per acre 

per day).

3.4

8.2 

10.5

Material.

Trickling effluent .......

....do..................

Analyses (parts per million) .

Nitrogen asFree 

ammonia.

426 

119 

74.2 

80.5 

31.8 

15.2 

1.6

Albuminoid 

ammonia.

113 

9.1 

3.1 

10.7 

3.8 

1.1 

.4

Nitrates 

and 

nitrites.

0 

0 

21.4 

0 

0 

25.7 

18.1

Oxygen 

consumed 

in 4 

hours 

at 

80° F.

330 

50 

21

77 

17.4

7

Suspended 

solids.

300 

45.6 

0 

0

The same principle was independently worked out by Corbett, 

the borough engineer of Salford, in a series of experiments begun 

in 1893 under the inspiration of the work of the Massachusetts 

State board of health. He first used wooden troughs for distribution and later fixed sprinklers, obtaining excellent results in the 

latter case. Ducat, another pioneer in the development of the 

tricklmg filter, urged the importance of thorough aeration, building 

filters with open sides to attain that end, and maintained that the 

aerobic process alone was entirely competent for the treatment of 

crude sewage. He installed a small filter at Hendon in 1897.
78 THE PURIFICATION OF BOSTON SEWAGE.

Finally, in connection with the development of this process, should 

be mentioned Scott-Moncrieff, who carried its principles to a logical 

extreme in a series of experiments at Ashtead in 1898. He believed 

that several different types of organisms were concerned in the purifying process and that their separate and successive cultivation 

under perfect aerobic conditions would give the most favorable 

results. He therefore constructed a series of nine trays of 1-inch 

coke, each 2 by 7 feet by 7 inches deep, arranged one over the 

other, with a space of 2 inches between each pair. The effluent 

from a "cultivation tank" was discharged on the upper tray by a 

tipping bucket at a rate of 1.3 million gallons per acre per day (0.14 

on the whole area of nine trays), and its passage through the series 

occupied from eight to ten minutes. The degree of purification 

attained, as indicated in Table XLII, was extraordinarily high.

TABLE XLII. Results of trickling filtration through Scott-Moncrieff's trays (Scott-Moncrieff,

1899).

[Parts per million.]

Effluents of 

First tray . . ..............................

Third tray. ...............................

Fifth tray . . ..............................

Nitrogen asFree ammonia.

103 

86.5 

74.2 

41.2 

33 

12.4 

14.4 

2.9 

1.7 

2.1

Albuminoid ammonia.

12.3 

10.3 

8.2 

4.9 

2.9 

1.2 

2.9 

2.5 

5.3 

4.9

Nitrites.

0 

9.9 

9

7.8 

6.6 

4.8 

5.1 

0 

0 

Slight tr.

Nitrates.

1.2 

1

4.8 

18.7 

27.6 

46.8 

44.2 

66 

73.2 

90

Oxygen 

consumed 

in 4 hours 

at 80° F.

98.4 

66.9 

57.7 

44.9 

17.3 

12.8 

15 

7.6 

4 

5.9

A plant of this type has been installed at Caterham Barracks, 

where it handles daily 16,000 gallons of very strong sewage at a 

rate of 0.4. Oxygen consumed is reduced from 92 to 27 parts per 

million, free ammonia from 149 to 50 parts, and organic nitrogen 

from 27 to 7 parts, with a formation of 90 parts of nitric nitrogen 

(Rideal, 1901). The German commission on its visit to England in 

1902 reported that the effluent from this plant was stable, although 

it contained 68 parts per million of nitrogen as free ammonia, 5.8 

parts of organic nitrogen, and 51 parts of oxygen consumed (Bredtschneider and Thumm, 1904).

It is not clear that there is any such complex division of labor 

between various classes of nitrifiers as Scott-Moncrieff postulates. 

Whether any important advantage is ta be gained by dividing a 

trickling filter into layers with air spaces between has never been 

definitely determined. At Salford Corbett found no, gain from dividing his filters into three or four successive heights of 20 inches each 

(Rideal, 1901). .
SEWAGE PURIFICATION BY TRICKLING PROCESS. 79

The general practice is to construct trickling filters in single beds, 

which are merely heaps of the selected filtering material. It is not 

necessary that such a filter should be tight as long as its bottom is 

built with sufficient slope to carry off the effluent. It is desirable 

that it should be underdrained'in some way in order to avoid clogging 

and to maintain a good air supply, passing upward, chimney fashion, 

through the filter. In some cases tile drains are so arranged as to 

form practically a false floor. The walls of the Ducat filter are built 

of open drain pipe inclined upward and connected with aerating 

drains at intervals in the body of the bed. The Whittaker-Bryant 

filters at Accrington and elsewhere are octagonal in shape, with walls 

of open brick and central open-brickwork aerating wells. Both these 

types are costly (Kinnicutt, 1902). Filters may be constructed more 

simply by merely surrounding the filtering material with a fence of 

upright palings. The Stoddart filter is a heap of coke or cinders of 

this sort on a sloping floor without any walls. The two quarter-acre 

trickling beds now in operation at Birmingham are essentially of this 

type (Watson, 1903). The oldest of these beds was built of slag 

graded upward from one-half inch to three-fourths inch, heaped up 

without underdrains, the outside being held together by iron bands. 

More recent filters are of one-half to 3 inch broken brick underdrained 

by a false floor of tiles.

The most difficult point in the construction and operation of the 

trickling filter is the distribution of the sewage over its surface. The 

ideal condition for aeration would be the discharge of sewage in a fine 

and even spray over the whole surface of the filter. On the other 

hand, there is some evidence that a too regular distribution favors 

alien growths, which clog the surface of the filter. Scott-Moncrieff 

and Ducat originally used tipping buckets and troughs placed at 

intervals over the filter, relying on the dash to distribute over intermediate areas. This plan has been tried at Hendon and Leeds. At 

the other extreme in principle is the Stoddart distributer as used at 

Horfield. It is practically a series of channels, over the sides of 

which the sewage overflows continuously, dripping from a series of 

points on the under side, 360 points being allowed to a square yard. 

Theoretically this should secure a very even distribution; but such 

channels are liable to buckle and it is difficult to keep them level. 

Furthermore, they are liable to clogging from fungous growth (Barwise, 1904). A more practical method than either the tipping bucket 

or the Stoddart drip distributor is the method of distribution under 

pressure through perforated pipes. This was developed at Salford 

after various other attempts with troughs and with a thin layer of 

sand laid over the surface of the main filter. Disk-like caps were 

placed over the openings of the pipes in some early experiments in 

order to secure a good spray for distribution. Then the attempt was
80 THE PURIFICATION OF BOSTON SEWAGE.

made to get a spray by the impact of two converging flows, and finally 

a special form of opening was designed to give a rotating movement 

to the stream. This system is in use on the new filters at Birmingham 

and works well when good pressure is available (Baker, 1904). Barwise (R. S. C., 1902 a) describes the use in Derbyshire of fixed perforated pipes with metal disks placed over the outlets for spraying, 

dosed intermittently by automatic flush tanks. The same principle 

is used at Chesterfield. At Accrington intermittently operated fixed 

sprinkler pipes gave poor results in some preliminary experiments 

(Bredtschneider and Thumm, 1904).

Many plants in England are equipped with still more complex 

revolving sprinklers operated either by the pressure of their own jets 

or by mechanical power. The Candy-Whittaker sprinklers at 

Accrington are of the former type. With this filter, as well as with 

that of Ducat at Leeds, it was thought that it would be of advantage 

to warm the sewage before applying it, and the temperature was 

raised about 4° by the steam of the pulsometer used for pumping. 

The heating seems of little advantage, and at Leeds was found actually harmful, since it promoted surface growths which tended to clog 

the filter. All revolving sprinklers require much attention to keep 

them in operation and are subject to grave derangement from weather 

conditions. Daily cleaning with brushes is necessary with many 

plants to prevent serious clogging of the openings. Even more elaborate than the ordinary revolving sprinklers is the Scott-Moncrieff 

distributor installed at Birmingham, in which a radial trough revolves 

about an axis at the center of the bed, its outer end resting on a 

moving wheel, sewage running in a thin film over a weir which extends 

for the length of the trough.

With regard to depth and material in trickling filters there may be 

considerable latitude. In a series of experiments at Salford, analyses 

from which are quoted in Table XLIII, no better results were obtained 

with an 8-foot filter than with one only 5 feet deep.

TABLE XLIII. Efficiency of trickling filters of different depths at Salford, England (Bredtschneider and Thumm, 1904).

[Parts per million.]

Suspended 

solids.

280 

40 

20 

0 

0

Oxygen 

consumed 

in 4 hours 

at 80° F.

58 

42 

40 

6.5 

5.5

Nitrogen asFree ammonia.

19.8 

16.5 

16.5 

5.3 

4.9

Albuminoid ammonia.

5.1 

4.5 

4.3 

2.1 

1.6

Bell testified in 1902, apparently with regard to the same filters, 

that the oxygen-consumed value for the 8-foot filter was 12, against
SEWAGE PURIFICATION BY TEIOKLING PKOCESS. 81

15 for the 5-foot bed. He considered this difference too little to pay 

for the increased depth (R. S. C., 1902 a). Whittaker, on the other 

hand, reports much better results with beds 9 feet deep than with a 

depth of 4 feet 8 inches (R. S. C., 1902 a). Probably 4 feet is the 

safest minimum, and greater depths are desirable because of the danger in shallow filters that streams of unpurified sewage may pass 

through channels, due to irregular packing of the material. Ducat 

recommended a depth of 5 feet when the effluent was to be discharged into brackish water, 8 feet for discharge into rivers, and 10 

feet for small streams. The period of flow through trickling beds 

varies, at Leeds, from two or three minutes with very coarse beds up 

to thirty minutes with fine material.

It is probable that there is a maximum amount of organic matter 

present in sewage which can be easily nitrified by the trickling process, 

and that additional action does not produce results commensurate 

with the cost of deep single niters or of double and triple beds. Thus 

at Leeds it was found that the rate of improvement in the effluent of 

three successive beds rapidly decreased, as shown in Table XLIV.

TABLE XLIV. Efficiency of trickling filters at Leeds, England (Dibdin, 1903). 

[Parts per million.]

Effluent No. 2. ..........................

Total 

solids.

1,760 

1,250 

1,060 

1,010

Suspended 

solids.

631 

275 

113 

110

Nitrogen as 

Free ammonia.

27.6 

18.5 

13.3 

9.7

Albuminoid 

ammonia.

12.2 

7 

5 

3.5

Oxygen 

consumed 

in 4 hours 

at 80° F.

127 

62.5 39.6- 

27.6

With regard to the best material for the construction of trickling 

filters, data have been collected in a number of the English experiments. At Salford slag was found somewhat better than polarite, 

gravel, coke, or clay (Bredtschneider and Thumm, 1904). At York 

a well-controlled series of investigations indicated, as shown in Table 

XLV, that coke and boiler slag (clinker) are slightly better than brick 

and blast-furnace slag.

TABLE XLV. Efficiency of trickling fitters of different material at York, England (Bredtschneider and Thumm, 1904)-

[Parts per million.]

..Itrog

Albuminoid 

ammonia.

13.9

1.4

1.2

.9

1

m as 

Nitrates.

0

18.4

18.8

23

22

Oxygen

in 4 hours 

at 80° F.

82.9

10

9.6

7.1

6.9

IRK 185 06 6
82 THE PUEIFICATION OF BOSTON SEWAGE.

Coal has been found especially favorable to the process. At Buxton the effluents from destructor breeze and coke showed, respectively, 0.8 and 0.9 parts per million of albuminoid ammonia and 0.8 

and 0.7 parts of nitrates, while a coal filter yielded only 0.4 part of 

albuminoid ammonia and 3.4 parts of nitrates (Barwise, 1904). 

Striking differences obtained at Tip ton are shown in Table XLVI.

TABLE XLVI. Efficiency of trickling filters of various types at Tipton, England (Barwise,

1904).

[Parts per million.]

Garfleld's coal-filter effluent.

Solids.

In solution.

827 

840 

807 

914

In suspension.

16 

9 

14 

3

Nitrogen as 

Free ammonia.

10.3 

7.4 

2.2 

1.6

Albuminoid 

ammonia.

1.9 

1.3 

.4 

.3

Nitrates.

0 

3.8 

7.4 

8.1

Oxygen 

consumed 

in 4 hours 

at 80° P. .

7.7 

5.8 

2.2 

2

On the whole, it seems probable that any hard,'smooth material 

will serve well for the trickling filter. Coal is perhaps most promising, but granite, flints, gravel, and hard clinker are all suitable.

The size of material used may also be varied considerably within 

certain limits. The elaborate experiments carried out by Reid at 

Hanley, cited in Table XLVII, indicated that fragments from threesixteenths inch up to 1J inches yielded almost identical results (Hanley, 1904). Barwise (1904) suggests one-eighth to one-half inch 

material. Among the witnesses before the royal sewage commission 

Garfield recommended one-sixteenth to three-sixteenths inch, Ducat 

one-eighth to one-half inch, Corbett three-sixteenths to three-fourths 

inch, Candy three-sixteenths to one-half inch for fine and threefourths inch to 3 inches for coarse beds, Harding one-fourth inch to 

1J inches for fine and over 3 inches for coarse beds, Whittaker 1 inch 

to 1J inches, and Stoddart 2 to 3 inches.

TABLE XLVII. Efficiency of trickling filters with material of various sices at Hanley, England (Hanley, 1904; WUcox and Reid, 1904).

Rectangular bed :

Circular bed :

Size of 

material, 

(inches) .

ISB to J 

JtoJ

T%tOj

itoj 

i to i 

1J to J

Analyses (parts per million) .

Solids.

Dissolved.

1,250 

1,050

1,120 

1,120

1,120 

1,130 

1,130 

1,130

Suspended.

629 

44

4 

3

2 

14 

7 

17

Nitrogen as 

Fre6 ammonia.

17.3 

15

.7 

.8

.8 

.3 

.3 

1

Organic.

6.3 

2.2

.2 

.3

.2 

.2 

.2 

.4

Nitrates.

0 

0

17.5 

17.3

16.6 

15.3 

16.2 

16.2

Oxygen 

consumed 

in 4 hours 

at 80° P.

38.5 

17.3

2.7 

2.8

2.4 

2.6 

2.5 

3.3

The rate at which trickling filters may be operated seems generally 

to lie between 1 and 3 million gallons per acre per day. Ducat and
SEWAGE PDEIFICATION BY TRICKLING PEOCES8. 83

Scott-Moncrieff recommend a rate of 1.2; Barwise suggests 1.5; Watson gives the figures quoted in Table XLVIII for current English 

practice. Still higher figures may be attained at times. At Salford 

the rate, at first 3, was raised to 6 without injuring the quality of the 

effluent (Bredtschneider and Thumm, 1904).

TABLE XLVTIL Depth and redes of trickling fliers (Watson, 1903).

Place.

Hyde. ..............................................................................

York. ..............................................................................

Deptb 

(feet).

9

8.5

5

9

6.5

9

Rate(million gallons per 

acre per 

day).

1.2

2.3

1.2

2.6

2.6

2.3

The analytical results produced by a number of English trickling 

filters are brought together in Table XLIX. It will be noticed that 

the process here is a true nitrification, producing considerable amounts 

of nitrate in the effluent. The purification is good, distinctly higher 

in general than that obtained by the double-contact process. The 

results as measured by oxygen consumed are plotted in fig. 8. The 

trickling effluents are in general better than those yielded by contact 

beds or sewage farms, if not quite equal to those produced in intermittent filtration.

TABLE XLIX. Efficiency of trickling jtttration. 

[Parts per million.]

Place.

Hyde..................

Do./. .............

Wolverhampton* ..... 

Yorkj

,r -Material.

(Sewage .....'

I Effluent... ..

jSewage. ....

Sewage .....

Emuent 

Sewage ..... 

Emuent . . . 

Sewage . . 

Effluent . 

Sewage . . 

Effluent . 

(Sewage. . 

\Effluent . 

/Sewage . . 

I Effluent. .

\Effluent . . .

/Sewage .... 

\Effluent...

Solids.

Total,

1,120 

1,000 

1,110 

1,010 

1,850 

1,020 

Ir820 

986 

1,470 

979

840 

719

Suspended.

187 

80 

229 

110 

768 

0 

850 

Trace. 

486 

81

Nitrogen as -.-, ~

Freeam-~ 

monia.

71.6 

2.5 

39.5 

5.1 

21.2 

8.1 

21.7 

6.2 

33.9 

11.7 

32.8 

1.9 

23.5 

3.2 

47.1 

23.8 

31.8 

2.1

AlbtLminoid ammonia.

4.6

1.5

13.2 

.8 

16.5 

1.6 

5.1 

tfl.3 

5.4 

<Z.9 

12.8 

1.4 

12.6 

.5 

9.4 

1.3 

3.3 

.6 

5.9 

.6

Ni-- 

trates.

12

7.8

9.6

4.5

12.1

6.2 

1.4 

16.4 

0 

113

Nitrites, and titrates.

0 

23.3

4.8

13.7

Oxygen 

consumed in 

4bours 

at 80° F.

49.9 

18.1 

147 

7.8 

14 

16.3 

57.5 

<«9.8 

59.7 <«8.4 

114 

<U0.1 

141 

<«3.4 

116 

12.1 

43.3 

3.6 

42 

6.6

o Thermal aerobic filter, September 19 to October 19, 1898, receiving septic effluent (Rideal, 1901).

6 Ducat filter, October 14, 1898, receiving crude sewage; single analysis (Rideal, 1901).

c Whittaker bed No. 1, March 9, 1899, to May 8, 1900, receiving septic effluent (Martin, 1905).

d Analysis made of the rough settling of suspended solids.

e Whittaker bed No. 2, September 2, 1899, to January 30, 1900, receiving septic effluent (Martin, 1905).

/ Ducat filter, March 29 to April 30, 1900, receiving crude sewage (Martin, 1905).

g Ducat filter, June 13 to July 7, 1900, receiving crude sewage (Martin, 1905).

ft Leeds filter, December 13,1900, to January 14, 1901, receiving crude sewage (Martin, 1905).

» Coal filter, January 1896, to September, 1898, receiving chemical effluent (R. S. C., 1902a).

;' Septic effluent.
84 THE PUKIFICATION OF BOSTON SEWAGE.

ISO125-

100-

75-

50-

25-

RAW SEWAGE EFFLUENT

FIG. 8. Comparison of sewages and effluents from trickling beds, showing oxygen consumed, in parts

per million.

Barwise (1904) gives a number of analyses of effluents covering 

shorter periods, which are summarized in Table L.

TABLE L. Analyses of trickling-JUter effluents (Barwise, 190Ji).

Place.

Dronfield. . ............................................

Rate 

(million 

gallons 

per acre 

per 

day).

0.5 

.5 

1 

1 

1 

1 

1

Analyses (parts per million) .

Nitrogen as 

Albuminoid 

ammonia.

0.6 

.4

.2 

.5 

.7 

.2 

.2

Nitrates.

19.3

8.7 

4 

18 

6 

2.5 

13

Oxygen 

consumed 

in 4 hours 

at 80° F.

0.3 

.1 

.1 

.1

.7
SEWAGE PURIFICATION BY TRICKLING PROCESS. 85

The effluent of the trickling filter contains, as a rule, a certain amount 

of flocculent organic matter which mars its appearance, but this matter has been more or less completely oxidized and is of a stable, humuslike character. The effluents look worse and keep better than would 

be expected from their analyses. Clark has brought out this difference in a series of experiments summarized in Table LI. In each case 

the effluent was allowed to stand in a stoppered bottle in the laboratory, samples being withdrawn at intervals. To judge by free ammonia and oxygen consumed, both contact effluents were, at the start, 

better than those from the trickling filters. It was evident, however, 

that 

The large amount of residual organic matter in the effluents of filters Nos. 135 and 136 

had been, owing to the aerobic conditions prevailing in these filters, as evidenced by the 

high nitrates in the effluents, so changed by the bacteria and air that it was in a fairly stable 

condition. The effluents of these two filters Nos, 135 and 136 contained dissolved 

oxygen; at the end of the period of experiment, notwithstanding the large amount of organic 

matter present, no putrefaction took place, odors did not develop, and the organic matter 

present remained practically without change. The effluents of filters Nos. 137 and 163 contained less organic matter than the effluents of filters Nos. 135 and 136, but were, nevertheless, in a much lower state of nitrification; dissolved oxygen either was not present or disappeared quickly, and putrefaction occurred. Instead of the amount of nitrogen present 

as free ammonia remaining constant, as in the effluents of filters Nos. 135 and 136, it increased. 

The amount of oxygen consumed, instead of decreasing, increased eventually in the effluent 

of filter No. 137, and the anaerobic actions in the bottles containing this effluent and the 

formation of gas were quite noticeable, odors developing also. [Clark, 1902.]

The suspended solids may be easily removed from the trickling 

effluent by a short sedimentation. When so separated they are sometimes in themselves putrescible (R. S. C., 1902 a), but usually show 

only a small proportion of unstable matter. At Leeds (1900) analyses of the dried sediment from a trickling-filter effluent showed the 

following composition: Organic matter, 31 per cent; mineral matter insoluble in acids, 19 per cent; other mineral matter, 19 per cent. 

The clear liquid and the suspension which. comes fresh from the 

trickling filter are stable when the bed is operating properly.

TABLE LI. Comparative stability of stored effluents from contact and trickling filters (Clark,

1902).

TRICKLING FILTER NO. 135.

Time elapsed (days) .

0. .........................

7...........................

14..........................

21..........................

28..........................

Nitrogen as 

Free 

ammonia.

Albuminoid ammonia.

Total. In solution.

Nitrates. Nitrites.

Oxygen 

consumed 

in 2 minutes' boiling, corrected for 

nitrites.

Parts per million.

20.1 

18.2 

19.4 

19.4 

20.1

2.3 

2.2 

1.9 

2.1 

2

1 

.8 

.7 

.8 

7

51.8 

44.2 

49.1 

46.2 

39.4

0.1 

6 

1.1 

1.3 

2

24.4 

19.5 

20.9 

21.5 

21.3

Oxygen 

dissolved 

(per cent 

of saturation).

34.3 

15.3 

9.9 

13.2 

7.7
86 THE PUBLICATION OF BOSTON SEWAGE.

TABLE LI. Comparative stability of stored effluents from contact and trickling fMers (dark,

1902} Continued.

TRICKLING FILTER NO. 136.

Time elapsed (days).

0. ..........................

7...........................

14..........................

21..........................

28..........................

Nitrogen as 

Free 

ammonia.

Albuminoid ammonia.

Total. In solution.

Nitrates.

*

Nitrites.

Oxygen 

consumed 

in 2 minutes' boiling, corrected for 

nitrites.

Parts per million.

13.2 

13.2 

13.2 

13.2 

13.5

2.4 

2.1 

1.9 

1.8 

1.9

1 1

7 

6 

6 

6

52! 8 

50.8 

49.7 

47.3 

44

0.1 

1.1

.5 

.2 

0

25.6 

19.4 

18.3 

17.1 

18.4

Oxygen 

dissolved 

(per cent 

of saturation).

51.7 

15.5 

5 

1.6 

.3

CONTACT FILTER NO. 137.

0...........................

7... ........................

14..........................

21..........................

28..........................

21.4

23.1

23.9

26.4

26.4

1.8

1.6

1.4

1.3

1.1

.8

.9

6.2

.1

.1

.1

.1

0.2

0

0

0

0

17.4

22.8

24.8

23.2

0

0

0

0

0

CONTACT FILTER NO. 163.

0. .......................... 7.......:...................

14..........................

21..........................

28..........................

14.8

14.8

15.1

16.2

17.4

1.3

1.1

.6

.6

.6

.4

6.6

5.3

1.6

2.5

0.1

0

0

0

.2

il.8

10.8

10

9.4

8.6

46.2

0

0

0

0

The trickling filter comes into direct competition with the doublecontact system of sewage treatment, and it is necessary in every individual case to determine which of the two methods is most suitable. 

A comparison of the general features of the methods indicates that 

"on the whole the advantage rests with percolating filters" (Barwise, 

1904). It has been pointed out (p. 73) that the trickling filter is simpler in theory, since it depends on the uninterrupted maintenance of 

a single process of aerobic oxidation. The construction of the body 

of the bed is cheaper, since the trickling filter need not be made tight 

and can be built entirely without walls. In operation the advantage 

probably rests with the contact bed, since the methods of distribution 

on the trickling filter, as so far developed, are expensive when working 

well and are liable to get out of order. Since, in principle, the operation of the trickling filter is simplicity itself, it seems that the mechanical difficulties involved should not be insuperable. The operation of 

trickling filters under severe climatic conditions apparently does not 

present serious difficulties. At Leeds winter weather produced no 

derangement of beds or distributors. In America the problem is 

somewhat more serious. The spray filters at the Columbus experiment station appeared to the casual observer (Winslow, 1905) to be 

working well in the severe winter of 1904-5; but it is certain that 

many of the complicated English distributors could never be operated 

in this climate.
SEWAGE PURIFICATION BY TRICKLING PROCESS. 87

With regard to rate and its converse, required area, the advantage 

is all on the side of the trickling filter. Double-contact beds 6 feet 

deep can not be operated at a rate over 0.5 million gallons per acre per 

day (calculated on the combined area of the two beds). With trickling filters, on the other hand, a rate three or four times as high may 

easily be attained. It was estimated at Leeds that 17 acres of trickling filters could be substituted for 165 acres of double-contact beds. 

With regard to the results produced, it must be concluded that the 

trickling effluent is generally superior to that of the double-contact 

bed. It is more turbid, but contains less organic matter and shows 

greater stability. Finally, the trickling filter is apparently not subject to so serious clogging as the contact bed. What little clogging 

occurs does not interfere with the capacity of the beds. Furthermore, deposits may easily be washed out of the filter, and this washing 

is to a great extent accomplished automatically at times of storm. It 

seems even possible that in some cases crude sewage may be handled 

by the trickling filter. Harding says: *.

In the case of Leeds, I must say I do not see that there is any necessity for antecedent 

septic action, and if it proves practicable, as I think it will, to devise an automatic screening 

apparatus to take off the grosser solids, I think it would be possible to put crude sewage 

with finely divided solids direct upon a continuous filter and then have a settling tank at the 

end of the process, instead of at the beginning, or if the land is available, as it would be 

probably for the Leeds works, pass it overland for the purpose of mechanically separating 

filtering the suspended solids. [R. S. C., 1902 a.]

As evidence against the trickling process it should be noted that 

at Belfast Letts obtained very poor results with the trickling filter 

when filtering septic effluent. He used the Stoddart distributer, and 

his bed was 3 feet 9 inches deep, filled with 6-inch clinker. The purification was less than that obtained in parallel experiments at lower 

rates with a single-contact bed (Martin, 1905). The large size of 

the material used and the poor distribution seem to have vitiated this 

experiment. At Manchester a Stoddart filter of coarse clinker 2 to 

3 inches, dosed with septic effluent, was tested in 1900. The effluents 

were of fair quality, but so turbid as to require settling (Manchester, 

1901). Again, in 1902 a desultory experiment was made by dosing 

a second-contact bed with a sprinkler and leaving the outlet open. 

The secondary bed received six fillings a day, each occupying about 

an hour, so that it worked as a sort of trickling filter for a quarter of 

the time. A comparison of the effluent obtained in this way with 

that from the secondary bed operated as a contact bed showed that 

the latter process gave distinctly better results.

It should be mentioned that several determinations which have been made show that 

there is more dissolved oxygen in the filtrate from bed D when this bed is worked continuously than when it is worked as a contact bed; there is, however, invariably more suspended 

matter in the former case. It is no doubt owing to this suspended matter that the percentage purification results above given are unfavorable to the sprinkler. [Manchester, 1903.]
THE PURIFICATION OF BOSTON SEWAGE.

With the exception of these incomplete and inconclusive studies, 

the evidence of comparative tests favors the trickling process. At 

Leeds the matter was studied most exhaustively. The analytical 

results, as indicated by the figures quoted in Tables XXXVI and 

XLIX, were slightly better for the trickling process than for the 

contact beds, with rates threefold higher. While contact beds clogged 

badly even with septic effluent, the trickling beds, if built of coarse 

material (over 1J inches), maintained their efficiency (Leeds, 1900). 

At York an elaborate series of comparative experiments was carried 

out in 1899 and indicated a marked superiority for the trickling filter 

(York, 1901). The principal analytical results are summarized in 

Table LIT.

TABLE LII. Results of experiments at Naburn disposal worlcs, Yorlc (York, 1901).

Conditions.

Closed septic tank and singlecontact filters, August, 1899,

Crude-sewage and double-contact beds, August to October 1899

Ladder filter, August to NoOpen septic tank and continuous filter, July, 1900, to AuOpen septic tanks and doublecontact beds, November,

Material.

Sewage . . . 

Effluent . .

Sewage . . . 

Efiluent . .

1 Sewage . . . 

J Efiluent . .

1 Sewage . . . 

[Efiluent . .

[Sewage . . . 

J Effluent . .

Rate 

(million 

gallons 

per acre 

per day) .

0.5

.2

.4

2.6

.2

Analyses (parts per million).

Total 

solids.

872 

571

819 

711

897 

950

840 

719

876 

645

Nitrogen asFree 

ammonia.

33.6 

19.7

38 

9.8

38 

25

31.8 

2.1

24.7 

4.6

Albuminoid ammonia.

5.1 

1.8

4.2

1.2

4

2.5

5.9 

.6

6. 3

.8

Nitrates.

8.3

0 

0

113

27.6

Oxygen 

consumed 

in 4 

hours at 

80° F.

31 

11

33 

6.3

33

18

42 

6.6

42 

9.1

At Accrington trickling filters have been substituted for contact 

beds (Baker, 1904); and the same change is contemplated at Heywood 

(Bredtschneider and Thumm, 1904).

EECENT TENDENCIES IN SEWAGE-DISPOSAL PRACTICE IN ENGLAND, 

GERMANY, AND THE UNITED STATES.

Advances in the art of sewage disposal by processes of rapid treatment have been made almost wholly in England. It is natural that 

such should have been the case, since the concentration of population in that country renders some method of treatment necessary 

and since the lack of sandy soil makes the method of intermittent 

filtration impracticable. We have seen that the first steps were 

taken by Dibdin in the London and Sutton experiments of 1892- 

1896, which proved that the contact bed was capable of successfully 

treating sewage at high rates. Meanwhile Cameron's septic tank, 

installed at Exeter in 1896, was demonstrating the anaerobic process 

of preliminary treatment. At both Sutton and Exeter septic tanks
KECENT TENDENCIES IN SEWAGE DISPOSAL. 89

followed by contact beds have since been installed (Baker, 1904). 

At London the system of chemical precipitation remains essentially 

as it was in 1892. The experiments carried out by Clowes and Houston in 1898-1901 led, however, to the recommendation that instead 

of this process there be substituted (a) sedimentation of mineral matter, (6) septic treatment in tanks of six hours' capacity, and (c) treatment in single-contact beds of coke 6 feet deep (Clowes and Houston, 

1904).

The next important series of investigations was that carried out 

at Manchester. This city, the third metropolis of England, has a 

population of half a million and a daily flow of 42 million gallons of 

strong industrial sewage. Chemical precipitation was introduced in 

1894, but th& effluent created a nuisance in the ship canal into which 

it was discharged. No land was available for treatment, and in 1898 

a commission consisting of Baldwin Latham, Percy Frankland, and 

W. H. Perkins began a series of experiments on the newer rapid 

methods. The first report, made in 1899 (Manchester, 1900 a), concluded that in spite of the presence of industrial wastes, the "bacterial system is the system best adapted for the purification of the 

sewage of Manchester." The experts believed that double^contact 

beds would produce a satisfactory effluent. " It may be taken broadly 

that in the first contact 50 per cent of the dissolved impurity is removed and that in the second contact 50 per cent of the impurity 

still remaining in the effluent is disposed of." They held that "in 

order that a bacterial contact bed may exercise its full powers of 

purification, it is necessary (a) that it should be allowed sufficiently 

frequent and prolonged periods of rest; (&) that the sewage applied 

to it should, as far as possible, be free from suspended matters; (c) 

that the sewage applied to it should be of as uniform a character as 

possible." They therefore recommended the installation of open 

septic tanks and double-contact beds. The secondary beds have not 

yet been constructed, but 46 acres of primary beds were in operation 

in 1904 (Baker, 1904).

The next important investigations were carried out at another 

great manufacturing center, Leeds. Here some experiments were 

made in 1870 which led to the adoption of chemical precipitation. 

In 1894 a special commission recommended broad irrigation, but 

sufficient land was not available. In 1897 investigations were begun 

by T. Hewson, W. H. Harrison, and T. W. Harding, and reports have 

been made in 1898, 1900, and 1905. It was found that the doublecontact process gave good results with crude sewage and excellent 

results with septic effluent, but that serious difficulty was experienced in maintaining the capacity of the primary beds. Trickling 

filters of fine material gave good results, but clogged badly.
90 THE PURIFICATION OF BOSTON SEWAGE.

On the other hand, continuous filtration over very coarse material of septic effluent and 

even of crude sewage has given interesting and remarkable results if the solids in suspension 

which come out in the effluent are settled after filtration. These solids are nonputrescible, 

can be readily settled, and the drying does not give rise to evil odors. It would seem that the 

coming through of these solids, which for the most part are not further reducible and largely 

mineral, insures the permanence o"f the coarse beds.

It has been found practicable for long periods to work coarse, continuous beds 10 feet 

deep at the rate of 200 gallons per square yard, or 1 million gallons per acre per day, for septic 

effluent. At this rate results giving over 90 per cent purification are obtained after settlement of solids coming out in the filtrate; and although at this rate some of the solids are 

retained in the filter and there accumulate, they can be washed out by the increased flow 

which naturally arises with storm dilution. This possibility of dealing with storm waters is 

an important feature of the system.

It would seem practicable to deal with crude sewage (previously strained through several 

screens): but in this case a depth of 12 feet of material would be required for Leeds sewage, 

which is not very strong. These latter experiments have not been carried on long enough to 

draw from them any definite conclusions. [Dibdin, 1903.]

It was finally recommended by the Leeds experts that coarse, trickling filters be installed, either preceded by septic or chemical treatment 

or followed by subsequent sedimentation. Construction has been 

delayed on account of legal and political obstacles.

Birmingham, the fourth largest city in England, with a population 

of 800,000, has. faced similar difficulties. The discharge of sewage 

into the river Tame was begun in 1852. In 1859 experiments were 

carried out which led, in 1872, to the installation of chemical precipitation tanks and a sewage farm. Recently a most elaborate series of 

large-scale experiments, unfortunately never reported in print, have 

been carried out by Watson, the city engineer, and have indicated the 

application of biological processes. In 1900 a beginning was made by 

converting the precipitation basins into septic tanks. The sewage is 

now first settled for about four hours in tanks which are cleaned once a 

week. Thence it passes through the open septic tanks, which have a 

capacity of eight hours' dry-weather flow. No sludge had been removed 

from these tanks after three and one-half years of operation. The 

septic effluent is then treated on the largest farm in England, 2.830 

acres in extent, of which 1,784 acres are in actual use. The results of 

these various processes in 1902 are shown in Table LIII.

TABLE LIII. Results of sewage purification at Birmingham, England (Watson, 1903).

[Parts per million.]

Sedimentation-tank effluent . . .

Solids.

Dissolved.

1,280 

1,312 

1,180 

1,010

Suspended.

686 

346 

274

Nitrogen as 

Free 

ammonia.

39.3 

37.7 

48.1

1.7

Albuminoid ammonia.

14.2 

10.9 

8.3 

.1

Nitrates.

7 

7.3 

3.1

5.7

Oxygen consumed 

in 4 hours at 80° F.

Dissolved.

127 

149 

121 

19

Suspended.

60.3 

92.5 

71.8
REGENT TENDENCIES IN SEWAGE DISPOSAL. 91

It is planned in the future to settle the septic effluent in Dortmund 

tanks and to purify it by passage through trickling beds, of which 

four were in operation in 1904 (Baker, 1904).

Experiments second in importance only to those mentioned have 

been carried out at other large cities in England. At Leicester in 

1898-99 a series of investigations was made by E. G. Mawbey involving 16 combinations of detritus tanks, settling tanks, single, double, 

and triple contact beds, and land treatment. Most of these experiments were unfortunately of very short duration. At present the 

Beaumont-Leys sewage farm of 1,700 acres is still in operation, but the 

installation of settling tanks and single-contact beds is planned for the 

near future (Leicester, 1900). Huddersfield has a serious problem in 

the presence of large amounts of industrial waste from the scouring 

and dyeing of wool; but it was shown in a series of experiments carried out between 1898 and 1900 by J. L. Campbell that chemical 

treatment, sedimentation, and contact treatment would solve the 

difficulty satisfactorily (R. S. C., 1902 b). At certain hours of the day 

a single treatment would be sufficient, while at other times secondary 

beds should be used. Triple-contact beds treating crude sewage 

gave good purification, but clogged badly. At Oldham studies carried out by J. B. Wilkinson from 1898 to 1900 led to the adoption of 

sedimentation and single-contact beds (R. S. C., 1902 b). At York 

chemical treatment has proved unsatisfactory, and since 1899 investigations have been carried on by A. Creer, which, as shown in Table 

LII, indicated that septic tanks and trickling filters would best solve 

the problem. Large-scale experimental filters have been put in operation, but the final construction is not yet under way (Baker, 1904).

The review of existing conditions in 1904 published by M. N. 

Baker (1904) describes some of the most interesting plants in actual 

operation. At Manchester, Sutton, Exeter, Yeovil, Barrhead, Oldham, and Burnley he found septic tanks and contact filters. At Birmingham, Salford, Accrington, and York trickling filters were in 

operation. There is a strong general tendency to the conversion of 

old chemical-precipitation systems into septic tanks, except at Glasgow, where the former process is to be maintained. Sewage farming 

is not extending, although it has its strong advocates and many of the 

farms now in use operate satisfactorily. The popularity of doublecontact beds, at a maximum five years ago, seems already on the 

wane. Trickling filters, either preceded or followed by septic treatment or sedimentation, are growing in favor (Baker, 1904).

The general progress of sewage disposal in England has been seriously checked by the local government board, which enjoys extraordinary authority over any exercise of the borrowing power on the 

parts of municipal corporations. The sewage of towns commission
92 THE PURIFICATION OF BOSTON SEWAGE. ~

had reported in 1865 that "the right way to dispose of town sewage 

is to apply it continuously to land, and it is only by such application 

that the pollution of rivers can be avoided." The rivers pollution 

commission in its five reports from 1870 to 1874 recommended intermittent filtration as the best method for sewage treatment, with 

broad irrigation next and chemical precipitation last. The metropolitan sewage commission of 1882 reported in 1884 that chemical 

precipitation should be adopted by London and that the effluent 

should finally be treated on land. The local government board, on 

the strength of these precedents, has maintained a position of 

extreme conservatism, requiring, save in exceptional cases, that " any 

scheme of sewage disposal for which money is to be borrowed with 

their sanction should provide for the application of the sewage or 

effluent to an adequate area of suitable land before its discharge 

into a stream." The following detailed rules of the board were set 

forth in a circular issued in 1900: " In any sewage works three times 

the dry-weather flow must be treated, and an equivalent amount 

in addition must be provided for by special storm-water filters. 

Septic tanks or sedimentation basins must have a capacity equal to 

the dry-weather flow if followed by double-contact beds, and 50 per 

cent larger if followed by single-contact or trickling filters. Contact 

beds must not be over 4 feet deep and may receive two fillings a 

day, or three if automatic devices are provided. Their capacity 

shall be figured on an open space of 33 per cent with preliminary 

septic treatment or sedimentation and of 25 per cent with crude 

sewage. Trickling filters must be at least 6 feet deep and may 

operate at a rate of 1 million gallons per acre per day with crude 

sewage, which may be doubled with sedimented sewage or septic 

effluent. The effluent from either the contact or the trickling process must be subsequently treated on land, 1 acre being allowed for 

every 1,000 persons contributing sewage. With crude sewage on 

land 150 persons per acre is the limit."

In view of the experiments at London and Sutton and at Leeds 

and Manchester, such rules were an almost intolerable burden, and 

with these facts in view a new royal commission was appointed in 

1898, with the Earl of Iddesleigh as chairman, to determine "what 

method or methods of treating and disposing of sewage (including 

any liquid from any factory or manufacturing process) may properly be adopted." This commission made a first interim report of 

three volumes in 1901, a second on special chemical and bacteriological 

problems in 1903, and a third in two volumes on the treatment of 

trade effluents in 1903. Of a fourth report four volumes were issued 

in 1903 and 1904, three on the pollution of tidal waters, with special reference to contamination of shellfish, and a fourth (in five 

parts) on the land treatment of sewage. The first interim report of
EECENT TENDENCIES IN SEWAGE DISPOSAL. 93

1901 accomplished the chief work of the commission, since it contained the conclusion that 

It is practicable to produce by artificial processes alone, either from sewage or from 

certain mixtures of sewage and trade refuse such, for example, as are met with at Leeds 

and Manchester effluents which will not putrefy, which would be classed as good according to ordinary chemical standards, and which might be discharged into a stream without 

fear of creating a nuisance. We think, therefore, that there are cases in which the local 

government board would be justified in modifying, under proper safeguards, the present 

rule as regards the application of sewage to land. [R. S. C., 1901.]

The conclusions of the royal sewage commission throw open tbe 

way for progress, and the developments of the next decade may be 

watched with interest.

On the continent of Europe progress in sewage disposal has been 

much less rapid than in England. Germany is ahead of other countries in this respect, but even here the problem has not pressed 

heavily. The population is less dense and the rivers larger than in 

England. The installation of purification systems was slow, and 

when they were found necessary land for irrigation was generally 

available. The knowledge of the process of sewage farming dated 

from a visit to England made in the early seventies by a Berlin 

commission headed by Rudolf Virchow, and inspiration along more 

modern lines has similarly come from England. In 1897 of 43 

English cities with over 70,000 population 23 treated their sewage 

by irrigation or chemical precipitation. In Germany at the same 

time there were only nine cities'with over 70,000 population having 

disposal systems, of which three were precipitation works and six 

sewage farms (Kinnicutt, 1898).

The most important experimental work carried out in Germany 

has been that of the experiment station of the Hygienic Institute 

of Hamburg. This was founded in 1894 to test various sewagepurification processes and placed under the charge of Doctor Dunbar 

as director. Experiments on the contact process were begun in 

1897, and the studies at this station have done more than any others 

to elucidate the theory of the contact bed. The general results indicated that good effluents could be obtained from single-contact beds 

of fine material, but that under such conditions clogging occurred, 

which must necessitate the removal of the material for cleaning several times a year (Dunbar and Thumm, 1902).

Meanwhile Schweder had installed in 1897 an experimental septic 

tank and contact bed at Grosslichterfelde to treat part of the sewage of Berlin. A commission appointed by the Prussian ministry 

of the interior studied this plant in 1897-98 and arrived at the same 

conclusion which Dunbar had reached in the case of Hamburg 

(Bruch, 1899).

In 1901 the royal testing station for water supply and sewage 

disposal was organized at Berlin, and its annual communications
94 THE PURIFICATION OF BOSTON SEWAGE.

since 1902 have furnished a succession of papers of the greatest 

value. Unfavorable results were first reported from contact beds 

at Tempelhof and Charlottenburg. In 1901 Zahn (1901) on behalf 

of the station carried out a series of investigations at Charlottenburg (Westend) which showed that nonputrescible, effluents could 

be obtained with single contact. Experiments by Schury (1905) at 

Stuttgart led to similar results, septic treatment and single contact 

giving good results, little improved by secondary treatment. Trickling filters proved slightly better than contact beds.

The general trend of the German experimental work has till 

recently been in favor of single-contact treatment in beds of fine 

material, to be dug out and cleaned at intervals. Opinion is not 

favorable to the septic tank. Considerable interest has been recently 

manifested in the trickling filter, especially at Berlin.' In spite of 

the great importance of the Hamburg work in relation to theoretical 

questions, the writers can not feel that the German experiments 

have furnished a fair test of the modern biological processes. It is 

true that German sewage is strong and contains large amounts of 

industrial wastes, yet in addition to these facts it seems even to 

local observers that the experimental filters have not been operated 

with the judgment and skill necessary to secure the greatest practical efficiency (Thumm, 1905).

Actual practice in Europe outside of England is still largely confined to chemical treatment and irrigation. In Germany in 1904, 

according to the official charts exhibited at the St. Louis Exposition, 

there were 254 cities with over 15,000 inhabitants. Twenty of these 

had no sewerage system. Of the remainder, 132 discharged their 

sewage into water, 84 treated it by various chemical processes, and 18 

disposed of it on irrigation areas. Bredtschneider and Thumm were 

sent by the Berlin royal testing station and the city of Charlottenburg 

to study English conditions in 1903, and their report (Bredtschneider 

and Thumm, 1904), together with the results of the Hamburg and 

Berlin experiments, is likely to bear fruit in the near future. In 

France, too, active interest is manifested in the newer processes. A 

commission including MM. Calmette, Beckman, and Lannay visited 

England in 1900 to examine the works there in operation, and later 

experiments showed that the sewage of Lille could be satisfactorily 

treated in septic tanks and double-contact beds (Calmette, 1901).

In the United States sewage-disposal practice necessarily varies 

widely in different localities. New England, covered with a mantle 

of Glacial drift, finds the Lawrence method of intermittent filtration 

through sand eminently satisfactory. Following the construction of 

the beds at Framingham. in 1889 and at Gardner and Marlboro in 

1891, plants of this type have been rapidly added in Massachusetts 

till in 1903 there were 23 intermittent-filtration areas in the State
BECENT. TENDENCIES IN SEWAGE DISPOSAL. 95

(Massachusetts, 1904). In Connecticut in 1902 there were nine 

plants in operation, all sand filter beds (Connecticut, 1903).

West of the Appalachian Mountains soil conditions change, and 

available areas of sand become more and more difficult to obtain. 

The septic tank is frequently called in to remove solids and make 

possible the treatment of sewage at more rapid rates. The plants at 

Saratoga, N. Y. (Barbour, 1905), Lake Forest, 111. (Alvord, 1902), and 

Wauwatosa, Wis. (Alvord, 1902), are good examples of this type.

In the Middle West the newer biological processes are rapidly 

gaining a foothold.

The first septic tanks at Urbana, 111. (1894), and Champaign, 111., 

have been mentioned. Septic tanks have since been installed at 

Kewanee, 111. (1898), Fond du Lac, Wis. (1901), Madison, Wis.(1901), 

Mansfield, Ohio (1902), and a score of other places. The construction 

of contact beds began about 1900 and some dozen plants are now in 

operation, the most important being at Mansfield, Ohio (Pratt, 1905). 

In 1905 there were in Ohio 32 purification plants, of which 19 were sand 

filters and 7 contact beds; 13 made use of septic tanks at some stage 

in the process (Pratt, 1905). The only trickling filter of large size is 

at Madison, Wis.

Most of the plants in the Middle West are small and in many cases 

their maintenance is grossly neglected (Winslow, 1905). The city of 

Columbus is the first American municipality to approach the subject 

with a serious intention of finding the method of treatment best suited 

to local conditions. Here, under the direction of Hering and Fuller, 

a testing station was equipped in 1904, and a force of experts, including G. A. Johnson, W. E. Copeland, and A. E. Kimberley, carried out 

for a year an elaborate series of experiments. The station included a 

laboratory, one set of open tanks for preliminary treatment, and three 

sets of filters, with a gallery under a frame covering for each set. The 

sewage, amounting to about 350,000 gallons per day, was raised by a 

centrifugal pump to a screen chamber with two movable screens of 

three-eighths inch diagonal wire mesh. Next it passed to one of the 

tanks for preliminary treatment. These were seven in number, each 

40 feet by 8 feet, 8 feet deep at the upper end and 9 feet deep at the 

lower end, built of wood lined with galvanized iron. The first two 

tanks were called grit chambers, the sewage flowing through in about 

one and one-half hours. The other five tanks were either "plain 

sedimentation" or septic tanks, in which the sewage remained eight 

hours or more, the difference being that the former were emptied and 

cleaned whenever septic action began. In the septic tanks periods of 

eight, sixteen, and twenty-four hours were compared.

The sewage after treatment by one of these three preliminary processes (grit chamber, plain sedimentation basin, or septic tank) was 

purified by treatment in one or more of thirty-five experimental filters.
96 THE PUEIFICATION OF BOSTON SEWAGE.

These were cypress tanks 6 feet deep; one was 11 feet in diameter, 

four 12 feet lOf inches in diameter, and the other thirty 7Jfeet in 

diameter. They were all open filters and arranged for the most part 

in two blocks of two rows each, with a covered dosing and sampling 

gallery between the rows, in which all the engineering details of operation were regulated with the greatest accuracy. Twenty-one were 

intermittent sand filters, two primary and four secondary contact 

beds of broken limestone, two coke strainers, and six trickling filters. 

With this plant the widest possible series of combinations was tried, 

including sand niters, trickling filters, and contact beds alone, either 

of these preceded by plain sedimentation or septic treatment, and 

sand filters preceded by contact or trickling filters. The results of 

the experiments have led to the recommendation of septic treatment, 

followed by trickling beds.

Plans of the sewage-purification work for a nominal flow of 20 million gallons per day 

have been presented to the State board of health. The plans propose septic tanks followed 

by sprinkling filters. The septic tanks will be 12 feet in depth, uncovered, and will have a 

capacity of about 8 million gallons. The sprinkling filters will be about 10 acres in area, of 

broken stone, 5 feet in depth, laid on hollow free-draining bottom, with sprinkling nozzles 

15 feet, center to center, designed under a 5-foot head to spray the septic sewage over 

the surface of the broken stone,.at a net rate of 2 million gallons per acre per day. The 

effluent from these filters will be collected in settling basins with a capacity of 4 million 

gallons. [Griggs, 1905.]

In the extreme West a third set of conditions confronts the sewage 

expert. The arid climate here makes the sewage of special value for 

irrigation and the sparseness of population renders sewage farming 

the most profitable means of treatment. Following the early broadirrigation areas at Cheyenne, Wyo. (1883), Greeley, Colo. (1890), 

Hastings, Nebr. (1892), Los Angeles, Cal. (1892), and Trinidad, Colo. 

(1892), a dozen or more plants have been laid out and are in operation, the largest in 1904 being at Los Angeles, Cal., Salt Lake City, 

Utah, and Hastings, Nebr.

Chemical-precipitation plants, built before the newer processes were 

developed, are maintained at Alliance and Canton, Ohio, and at other 

places to avoid the cost of change. At Providence, R. I., on account 

of special local conditions, this process seems well adapted for continued use.

In a comprehensive review of conditions in the United States, 

Fuller (1905 a) states that of 1,524 cities and towns with a population 

over 3,000, 1,100 have sewerage systems and 90 have purification 

plants. Among these 90 plants are 14 irrigation areas, 41 intermittent sand filters, 13 chemical-precipitation works, 29 septic tanks, and 

10 rapid filters of coarse materials. The fact that of a population of 

28,000,000 connected with sewerage systems the sewage of 20,400,000 

is discharged into fresh water and of 6,500,000 into the sea furnishes 

some indication of the problem which must be met in the near future.
THE SEWAGE EXPEEIMENT STATION. 97

EXPERIMENTS ON THE PURIFICATION OF BOSTON 

SEWAGE, 1903-1905.

THE SEWAGE EXPERIMENT STATION. 0

The sewage experiment station of the Massachusetts Institute of 

Technology is situated in the southeastern portion of the city of Boston, near the corner of Albany street and Massachusetts avenue, at

ii ii 

ji i«

L.

\ rty*/ MILTON T I

xf y ^ t" "/C f' "- MAIN

"v -. ' f - > «&« ' \^!! N, r' 

^

SEWERS 

LIMIT OF SEWAGt DISTRICT

SCALE OF MILES

M.I.T. STATION

FIG. 9. Map of Massachusetts metropolitan sewerage district.

the point indicated by the star on the map (fig. 9). Connection is 

made with the 9-foot sewer of the Boston main drainage system at a 

point on Massachusetts avenue about 200 feet below the entrance of

« The foundation of this station and the object of the experiments are described in the introduction 

(pp. 5-9).

IBR 185 06 7
98 THE PURIFICATION OF BOSTON SEWAGE.

the Albany street intercepting sewer. Prior to October 14, 1904, sewage from the whole of Boston south of the Charles, with the exception 

of the Dorchester and South Boston districts, together with sewage 

collected by the south metropolitan sewerage system from Waltham, 

Newton, Watertown, Brighton, and Brookline, flowed past the station 

intake. This contributory area is shown in fig. 9. In 1903-4 the 

flow above the station was more than 50 million gallons a day from a 

district with a contributing population of 350,000, sewered for the

FIG. 10. Plan of Massachusetts Institute of Technology experiment-station grounds and buildings.

most part on the combined system. Since October, 1904, the completion of the new high-level sewer and of the Ward street pumping 

station has resulted in the diversion of ail the sewage from the metropolitan district, outside of Boston proper, to the new sewer, diminishing the average daily flow past the station intake by about 

one-fourth. The location of the station and of the intake pipe with 

reference to the sewers is best seen in the accompanying ground 

plan (fig. 10).
THE SEWAGE EXPERIMENT STATION. 99

A 2J-inch galvanized-iron suction pipe runs directly to the station 

pump from a point in one of the sewer manholes about 10 feet below 

the surface of the street. To the lower end of this pipe is coupled a 

20-foot length of rubber suction hose of 3 inches internal diameter. 

This hose would reach to the bottom of the sewer in the absence of any 

flow, but is carried by the strong current to a nearly horizontal position at its lower end, so that it is suspended at about mid-depth. 

The flow is so strong that the sewage is well mixed throughout. At 

the end of the hose is a strainer made from a 3-foot length of 6-inch 

wrought-iron pipe in which eight ^-inch longitudinal slots have been 

cut from a point near one end through the other end. The open end 

is protected by a plate fastened within and having deep notches cut 

radially to correspond with the slots in the pipe. Such a device is 

found to be largely self-cleaning, allowing a free movement toward 

the end, of any material which is drawn lightly into one of the slots. 

Strainers of the ordinary type clog badly. Even with the slotted 

pipe the end must be hauled up each day, or oftener, and the rags 

and other material collected on it removed. The rubber suction 

pipe is joined to the iron pipe above it by a "quick-as-a-wink" 

coupler, a clamping device sometimes used in fire apparatus for 

making quick connections without screwing. With this coupler the 

entire suction pipe can be disconnected and hauled up without bending it a method which it is necessary to adopt in cleaning the end 

at times of very high water. Just before reaching the pump the suction pipe passes through a grit chamber, where it deposits the heavier 

particles of sand and cinders. This chamber was put in at the suggestion of Mr. Leonard Metcalf, who furnished its design and other 

friendly suggestions. It consists of a cast-iron cross of stock waterpipe pattern. The diameter of the large arm, which rests vertically 

and constitutes the chamber, is 19 inches and its depth 16 inches. The 

other arm is 2J inches in diameter and connects with the suction pipe 

by flanges. Blank flanges form the top and bottom of the chamber and 

are bolted on and made tight by rubber packing, so that the top of the 

chamber may be readily removed for cleaning. A vertical grating of 

half-inch square iron bars, placed so as to give a clear space of half an 

inch between them, divides the chamber into two parts and serves to 

retain any rags or other large material which may have escaped the 

suction strainer. The chamber is placed on the line of the suction 

pipe 8 feet below the surface of the ground and is covered by a heavy 

frame structure of pyramidal form, 6 feet square on the bottom. 

From the grit chamber the suction pipe runs direct to the cellar of the 

filter house. Details of the grit chamber are shown in fig. 11.

The filter house is a two-story frame structure, the interior arrangement of which is made clear in figs. 12, 13, and 14. Fig. 12 is the 

ground-floor plan, showing the arrangement of the filter tanks and
100 THE PURIFICATION OF BOSTON" SEWAGE.

the pump pit. Fig. 13 is a plan of the second floor, indicating the 

position of the supply tanks, septic tanks, and sand filters. Fig. 14 

is a midsectional elevation bringing out the vertical arrangement of 

the various parts of the plant.

Section ofmanho/e

CGf/t chamber 

§

Scale of feet

I 2

FIG. 11. Detail of grit chamber.

The position of the pump is shown in fig. 12. It is a 4 by 6 

duplex Warren power pump driven by a 2-horsepower induction motor 

under 110 volts alternating current of 66 frequency. The plunger is of 

the cup type. It is found that this form protects the composition 

lining of the cylinder much more perfectly than a packed plunger.
THE SEWAGE EXPERIMENT STATION. 101

The valves are of the clapper type, with rubber packing, which is 

frequently renewed. The pump is placed in a pit 7 feet below the

floor of the filter house. The total suction lift is 16 feet, reckoned 

from the average dry-weather elevation of the sewage surface to
102 THE PUKIFICATION OP BOSTON SEWAGE.

the pump valves. This lift may be increased to 20 feet at times 

of low flow. -The pump is supplied with a vacuum gage, which

enables the attendant to see at a glance whether or not the valves 

are performing their duty and whether any stoppage of the strainers has occurred.
THE SEWAGE EXPEKIMENT STATION. 103

The sewage is delivered through a 2-inch force main to supply 

tank A, best shown in the sectional elevation (fig. 14). The lift 

from the pump valves to the tank is 25 feet. The supply tank is 

4 by 6 feet in area and 2 feet deep. The sewage enters the tank 

over the side near one end, passes over the weir shown in the section, and thence through pipes to supply tanks B and C and to the 

various filters. Tanks B and C are each the size of A and are connected with each other by holes through the dividing partition. 

They serve primarily to give a constant flow through the septic 

tanks, which are placed at a lower level on the same floor, and to 

the trickling filters on the floor below. The two tanks have a combined capacity of about 700 gallons, which is a two hours 7 supply 

for the continuously working tanks and filters.

Filters Nos. 1 and 2 are sand filters. Tank No. 1 is a cypress tank 

4 by 6 feet in area and 3 feet deep. It contains 2 feet of common 

Glacial drift sand with an effective size of 0.17 mm. and a uniformity coefficient of 3.5. This layer of sand rests on 6 inches of underdrain material graded from 4-inch cobbles at the bottom to buckwheat gravel just beneath the sand. The outlet of the filter is a 

1-inch iron pipe open at all times and not trapped. Filter No. 2 is 

like filter No. 1 in all respects, except that it contains a layer of 

sand but 1 foot thick over the underdrain material. The two tanks 

are built together, as shown in fig. 13.

The six septic tanks, numbered 5 to 10, are also built in pairs 

and are of the same dimensions as the sand-filter tanks, namely, 

4 by 6 feet and 3 feet deep. Tanks Nos. 7 and 9 are uncovered. 

The other four are covered as tightly as possible with wooden covers. These covers are not absolutely gas tight. Tank No. 6 is 

filled with crushed stone about 1J inches in diameter. All the 

tanks and filters on this floor, except No. 10, drain into small catch 

basins connected with the main drainpipe underneath the floor. 

This arrangement is shown in fig. 14. Each drainpipe may be 

closed off from the main drain by a cock just above the latter and 

the tank effluent diverted to the filters below. Tank No. 10 drains 

directly into the small tank D, which is 2 by 6 feet and 2 feet deep. 

This is used to flood a contact filter below.

Filter tanks Nos. 11 to 16 are all cypress tanks 4 feet square and 

6 feet deep, built together in pairs. Tanks Nos. 17 to 20 are of the 

same area, but only 4 feet deep. The pair Nos. 19 and 20 are at a 

higher elevation, so that their effluents can flow to the other pair, 

Nos. 17 and 18, respectively.

Tank No. 15 is a trickling filter, receiving the septic sewage from 

tank No. 5. Tanks Nos. 11 to 14 and Nos. 16 to 20 are contact filters. 

Tank No. 11 is filled with coke 2 to 3 inches in size; tanks Nos. 12, 

15, 19, and 20 with crushed stone 1 inch to li inches in size, and
104 THE PUEIFICATION OF BOSTON SEWAGE.

tanks Nos. 13, 16, 17, and 18 with one-fourth to one-half inch 

crushed stone. Tanks Nos. 17 and 19 constitute one double-contact

system and Nos. 18 and 20 another. Tank No. 14 is the only one 

which has been altered during the experiments. During the first
THE SEWAGE EXPEKIMEWT STATION. 105

year it was filled with crushed stone between one-half and 1 inch in 

diameter. In June, 1904, it was emptied and filled with Raritan 

facing brick, 1J by 4 by 12 inches, so laid in even tiers as to give 

the maximum of open space. Tank No. 22 is 4 by 4 by 6 feet, and No. 

23 is 4 by 2 by 6 feet, the two tanks forming a pair. They are 

filled with 1 inch to 1J inches crushed stone and are operated as 

trickling filters. Sand filters Nos. 24 and 25 are exact counterparts 

of filter No. 1. The filters on the lower floor all drain into catch 

basins similar to those on the upper floor already described. These 

empty directly into a main drain underneath the floor. In the case 

of filters Nos. 15 and 22 the effluent runs into a barrel provided 

with an overflow. These barrels provide a two hours' storage for 

the effluents, so that the effect of that period of sedimentation may 

be studied. The barrel under filter No. 15 is shown in fig. 14. 

Tank M is used as a measuring tank. It is fitted with a float gage, 

carefully calibrated, reading by means of a vernier to the nearest 

gallon. The principal statistics of the tanks and filters are brought 

together in Table LIV for convenience of reference.

TABLE LIV. Statistics of experimental tanks and filters.

No.

1

?,

3

4

fi

6

7

8

9

10

11

12

13

14

15

16

17

18

19?n

W,

23

24

flfl

Dimensions 

(feet).

4 by 6 by 3 

4 by 6 by 3

4 by 6 by 3

4 by 6 by 3

4 by 6 by 3

4 by 6 by 3

4 by 6 by 3

4 by 6 by 3

4 by 4 by 6

4 by 4 by 6

4 by 4 by 6

Description.

Intermittent sand filter. ....................... 

.....do..........................................

.....do..........................................

.....do..........................................

.....do..........................................

.....do..........................................

.....do..........................................

.....do..........................................

.....do..........................................

trickling filter. ................................

.....do..........................................

.....do..........................................

.....do..........................................

.....do..........................................

Trickling filter. ................................

.....do..........................................

Material.

Sand ..... 

.....do....

.....do....

/Stone.....

.....do....

.....do....

.....do....

.....do....

.....do....

.....do....

.....do....

Sand.....

.....do....

Size.

0.17 millimeter. 

Do.

} to 1 inch.

J to 1 inch.

Do.

Do.

Do.

Do.

Do.

Do.

According to the plan of the experiments each unit differed from 

each of several other units by only one variable condition. In this 

way the results of the whole series may be studied together as one 

experiment, and it is possible to note the results of changing any one 

variable condition, the others being constant* Among the variables 

which have been studied in this way $re, firs^, of course, the various 

types of purification processes and thte coioeident necessary variation 

in the rate of filtration. Then under each principal type of process 

two or more of the following conditions have been compared, the
106 TflU PURIFICATION OF BOSTON SEWAGE.

variables, as stated, being introduced one at a time: Different kinds 

and sizes of material, different depths of bed, single versus double 

contact, fresh versus septic sewage of different ages, and open versus 

closed septic tanks. With the sand filters four combinations have 

been studied, each differing from each of the others by only one of 

these variables; with contact niters, six combinations; with trickling 

niters, three; and with septic tanks, three, which, together with one 

primary comparison of the main types, makes a total of seventeen 

combinations of the variables mentioned.

On the sand niters Nos. 1 and 2 the volume of sswage applied has 

been measured by a float in the supply tank over the filter. The 

pump was stopped while these filters were receiving their doses. 

Sand filters Nos. 24 and 25 were dosed from the barrels shown in fig. 

12. These barrels contain the exact amount of one dose. Sewage 

was distributed over the surface of the sand filters by means of small 

wooden troughs with side openings at intervals. Application of sewage to the contact filters was made by means of a single half-inch pipe 

discharging horizontally over the filter. The filling was in all cases 

continuous, about half an hour being allowed for the process. The 

amount of sewage applied to the contact filter is of course its own 

liquid capacity multiplied by the number of doses applied daily. To 

obtain this value and also to study the progressive loss of capacity of 

contact filters under various conditions very careful measurements of 

the capacity of all the filters have been made at weekly intervals. 

For this purpose the measuring tank M was used. Connection with 

the filter outlet was made by means of a rubber hose, and the total 

effluent of the filter was run into the measuring tank after the height 

of sewage within the filter had been noted.

The trickling filters were dosed by means of tipping buckets,, long 

V-shaped troughs divided by a longitudinal partition into two equal 

parts. As one side fills the weight of sewage overbalances the system 

and the bucket tips, emptying the full side and bringing up the other 

side so that it receives the flow and tips in its turn. In this way the 

sewage is splashed in successive doses over the two halves of the 

filter alternately.

By connecting an ordinary cyclometer to this tipping bucket it has 

been possible to record the number of tips and indirectly the total 

flow. The apparatus was originally rated, and occasionally checked, 

by allowing the effluent to flow into the measuring tank for a period 

and comparing the readings of the cyclometer with those of the float

The closed septic tanks were regulated at their outlets, free communication being allowed with the supply tanks overhead. The 

open tanks were maintained at a constant level by overflow pipes 

and were regulated at the inflow pipe. All the^e tanks were under
ANALYTICAL METHODS AtfD HE8TTLTS. 107

the constant observation of an attendant both day and night, and 

the rates of flow were determined at frequent intervals by filling a 

10-quart pail.

In sampling, a representative sample of the crude sewage was 

obtained by allowing a portion of the regular pumpage to flow slowly 

into a tank of 540 gallons capacity, filling the tank in about three hours 

during each morning. The sewage in the tank was then thoroughly 

mixed and sampled. Trickling effluents and sand-filter effluents were 

collected whenever running. Contact-filter effluents were collected 

at about the middle of the discharge. Analyses of each effluent were 

made weekly and of the sewage five times a week.

ANALYTICAL METHODS AND INTERPRETATION OF RESULTS.

In the comparison of two sewages from different localities the term 

"strength" is often used in such a loose way that its significance is 

more or less obscure. Strictly the strength of a sewage is measured 

by the amount of certain elementary constituents which it contains, 

as, for example, the amount of nitrogen present. Only en such a 

basis can any fair comparison of sewages be made. The use in this 

connection of constituents so partial and changeable as the free or 

albuminoid ammonia or the oxygen consumed is misleading. These 

constituents are in a state of constant change in any given sewage, 

and hence can not satisfactorily determine its real strength. This 

point is well illustrated by the analyses in Table LV, taken from the 

reports of the Massachusetts State board of health for 1903 (Clark, 

1904). The first line represents a nine months' average of weekly 

analyses of the Lawrence street sewage taken directly from the 

sewer a fresh sewage. The second line represents analyses of the 

same sewage for the same period after it had been pumped through 

about half a mile of pipe and subjected to sedimentation and septic 

action.

TABLE LV. Comparison of fresh sewage at Lawrence with the same sewage after passing 

through long pipe, April to December, 1903 (Massachusetts, 1904)-

[Parts per million.]

Nitrogen as 

Free ammonia.

18.1 

39

Albuminoid 

ammonia.

5.8 

5.2

Total 

organic.

23.4 

13.3

The increase in the free ammonia and the decrease in the total 

organic nitrogen are characteristic of what occurs in stored sewage. 

Such partial values as are given by determinations of albuminoid 

ammonia and oxygen consumed do not, therefore, stand in any constant relation to the total figures for organic nitrogen and carbon,
108 THE PUEIFICATIOK OF BOSTON SEWAGE.

respectively and hence in different sewages give different proportions of the whole.

Total nitrogen and total carbon values are, then, to be desired in 

the study of sewage purification. The latter are out of the question, 

since there is no available method for this determination sufficiently 

simple for routine use. Total nitrogen values have also been generally ignored until very recently, and these experiments were nearly 

half completed before their paramount importance became evident. 

Throughout the present series of studies, therefore, the old determinations of free and albuminoid ammonia and oxygen consumed have 

been maintained. These must be taken for what they may be worth 

as roughly representative of the total organic matter.

In this connection it is useful to remember that both the free and 

the albuminoid ammonia in sewage increase with age, and that the 

ratio of albuminoid ammonia to organic nitrogen increases at a corresponding rate. In a fresh sewage the albuminoid ammonia is roughly 

one-third the free and the organic nitrogen generally over three times 

the albuminoid. As the albuminoid-free ratio decreases the organicalbuminoid ratio decreases at almost the same rate, and Fuller (1903) 

has found that the former ratio is roughly about one-twelfth the latter; put into algebraic form this becomes 

12 X albuminoid nitrogen _ organic nitrogen

ammoniacal nitrogen albuminoid nitrogen 

whence

organic nitrogen = 12 X (^uminoid nitrogen)*

ammoniacal nitrogen

This formula is only roughly approximate, but is perhaps the best conversion formula yet Revised.

The commonest method of measuring the work of a filter is by the; 

percentage of purification obtained when the amount of some one of 

its constituents is compared in the crude sewage and the effluent. 

Dunbar and Thumm (1902) have attempted to justify this practice 

on theoretical grounds, claiming that percentage of purification, figured on oxygen consumed, runs parallel with keeping properties, irrespective of the original strength of the sewage. It may be assumed 

that some such general relation exists and that for a given process of 

purification on a given sewage it might be found with some degree of 

accuracy, but that the result is of general application to filters of all 

tj7pes and sewages of all kinds seems, in the absence of further evidence, improbable. Even though it may be true that a certain type 

of filter would produce a stable effluent by oxidizing one-half its 

organic matter, it does not necessarily fyjlow that another type, 

working through characteristic and entirely different reactions, would 

produce the same result by the same percentage of oxidation. The
ANALYTICAL METHODS AND RESULTS. 109

amount of available oxygen in an effluent is also of importance in relation to its stability, and of two effluents showing exactly the same percentage of purification, one might be quite stable by virtue of its 

high nitrate and oxygen content and the other putrefactive owing to 

the absence of these substances. Such a difference is observed between 

effluents from a contact and a trickling filter. A contact filter running in a typical manner has already carried out during its cycle those 

secondary reactions by which oxygen and nitrates are used up for the 

oxidation of organic matter. Such an effluent is practically free from 

reserve oxygen and must for stability be purified to a much greater 

degree than would be the case with that from a trickling filter in 

which, by virtue of a reserve of oxygen, the oxidation may proceed 

after discharge.

The character of an effluent, with respect to its stable or putrescible 

character, is the thing of paramount importance. The effluent from 

a good sand filter will show so little organic matter and so high a 

nitrate value that there can scarcely be a moment's question about 

its quality after an inspection of the general analytical results. With 

the newer rapid processes of sewage treatment, however, effluents of 

such high purity are rarely obtained. In practice it is generally the 

aim to produce, not the best effluent possible, but merely one which 

can be discharged, under existing conditions, without creating a nuisance. Such a requirement may be fulfilled by an effluent containing considerable amounts of organic matter if two conditions be 

present: (1) A sufficient amount of reserve oxygen in the effluent to 

unite with all readily oxidizable organic matter and thus prevent 

the development of anaerobic conditions; and (2) a stability of the 

organic matter by virtue of which it does not readily undergo putrefactive decomposition. A measure of this quality of stability is the 

essential in judging of an effluent.

Endeavors have been made to develop a relation between the ordinary analytical data and the keeping qualities of an effluent. It 

must be confessed, however, that the determination of the oxygen 

consumed and of the various forms of nitrogen, while serving to 

identify undoubtedly good or bad effluents, fails to discriminate 

between a partially purified effluent which is perfectly stable and a 

similar one which is not. It is therefore necessary to fall back on a 

practical test of keeping quality as furnished by the incubator test. 

In this test, devised by Scudder (R. S. C., 1902 a) and since modified 

by others, the sample is bottled up and kept in the incubator at a 

warm summer temperature from three to five days. If at the end 

of that time it is still sweet and does not consume much more oxygen 

from permanganate than it did initially, it is pronounced a stable 

effluent.
110 THE PURIFICATION OF BOSTON SEWAGE.

In the tests at this station a modification of Scudder's method has 

been used. The sample, as in Scudder's work, was stored for five 

days at 37° and the oxygen consumed from permanganate was deter-, 

mined in the cold. In the Boston sewage and effluents, however, 

there are considerable amounts of readily oxidizable nonorganic 

materials, chiefly hydrogen sulphide. In order to exclude these 

substances the oxygen-consumed value was determined twice, once 

immediately on the addition of the permanganate and again after 

three minutes. The difference between the two results represents 

the true oxygen-consumed value. This method was suggested by 

Messrs. Johnson and Kimberly, of the Columbus experiment station.

The determination of total and suspended solids, which should 

form an integral part of every sewage analysis, was made for a considerable period. Unfortunately the enormously high chlorides in 

the Boston sewage, due to sea water, entirely masked the suspended 

solids when the determination was made in the ordinary way, and 

the direct determination of suspended solids by the Gooch crucible 

method was begun too late to get a large series of results. In the 

present paper, therefore, it is possible to report only, as an indirect 

measure of suspended solids, turbidity readings made with the Jackson turbidimeter (Jackson and Whipple, 1901), recalibrated for 

coarse material as described by Phelps (1905 a).

The determinations actually carried out on each sample in these 

experiments were as follows: Free and albuminoid ammonia, nitrates 

and nitrites, oxygen consumed and oxygen dissolved, turbidity, 

and odor. The. albuminoid-ammonia and oxygen-consumed determinations were made on both the filtered and unfiltered samples. 

In addition to these regular determinations, an average sample was 

collected during the week, by adding each day to a bottle a definite 

amount of sewage sterilized with chloroform. On this average 

sample weekly determinations were made of chlorides, sulphates, 

iron, and alkalinity.

Analyses were made according to the methods generally employed 

in this part of the country, as described by Richards and Woodman 

(1904). Permanent standards have been used for the ammonia 

readings, as suggested by Jackson (1900). For the nitrite standards 

the Jackson permanent standards were used during a portion of the 

time, but it was soon found that a dilute solution of fuchsine, made 

up to match the desired nitrite reading by eye, gave a perfect standard as far as shade was concerned and was sufficiently permanent 

for all purposes. This is essentially the method since described by 

Weston (1905). Nitrates were determined by the Brucine method 

of Noll (1901), as described by Farnsteiner and his associates (1902).
OHAEAOTER OF OKUDE SEWAGE. HI

For the oxygen-consumed determination the Kubel method was 

used, boiling for two minutes. In future work it is the intention to 

follow throughout the procedure outlined by the committee on 

standard methods of the American Public Health Association.

In tabulating the results of these experiments all ammonia, nitrite, 

and nitrate values are reported in terms of nitrogen, and all chemical 

results are expressed in parts per million. The dissolved oxygen is 

reported in this way rather than in the conventional form of per cent 

of saturation, since, while the latter method of expression may have 

had some significance in the study of surface waters, it has no value 

whatever in connection with sewage or filtration work in general. 

Owing to a change in the temperature of the water during treatment 

the results expressed in per cent of saturation may show an increase 

in the amount of oxygen, while in reality there is a marked decreaser

CHARACTER OF THE CRUDE SEWAGE.

During the two years of the operation of the sanitary research 

laboratory almost daily analyses of the crude sewage have been 

made. The sewage analyzed, as already explained, is a sample of the 

flow from 9 to 12 a. m. which has passed through the screen and grit 

chamber, drawn directly from the supply tank without any further 

chance for sedimentation or straining. The amount and character of 

the material previously removed from the grit chamber and supply 

tank are discussed on pages 115-116. Table LVI (p. 114) gives quarterly averages of the samples, taken, as a rule, on five days of each 

week. Yearly averages are also shown, the year being taken for convenience from June to June. Detailed studies of hourly and seasonal variations in the composition of the sewage have been previously 

reported (Winslow and Phelps, 1905).

The organic constituents of Boston sewage appear to be fairly normal in relation to one another. As stated above, regular determinations of the organic nitrogen were not made, but from the results of 

about fifty such determinations made at various times in the course of 

experimental work it may be stated that the average organic-nitrogen 

figure for the whole period would be about 20 parts per million. In 

this respect the sewage appears to be of about the same strength as the 

average sewage of Massachusetts cities, being slightly weaker than the 

sewages of Lawrence and Gardner (new system) and somewhat 

stronger than those of Framingham, Worcester, and Brockton.

The inorganic analyses of mixed weekly samples covering the calendar year 1904 showed an average of 2,300 parts per million of chlorine, 

15 parts of iron, 125 parts of alkalinity, as calcium carbonate, and 220 

parts of SO3 as sulphates. The high chlorine and sulphate values are
112 THE PURIFICATION OF BOSTON SEWAGE.

due to the large amount of sea water present in the sewage of Boston. 

If the chlorine normal to the sewage itself is assumed to be equal to the 

total nitrogen, as is commonly the case, a simple calculation shows

1903 

SEPT. DEC.

QUARTER-YEAR ENDING

1904 

JUNE SEPT.

1905 

MAR. JUNE

^300

Tt'MPERATURE

OXYGf. N CONSUMED

\

~REE/ MMOfJ/A

ALBUMINOID AMMONIA

FIG. 15. Composition of the crude sewage of Boston.

that the amount of chlorine present represents a volume of sea water 

equal to 11 per cent of the total volume of the sewage. This, however, is only an average value for the period. During each twelve 

hours the chlorine reaches a maximum figure of from 3,000 to 4,000
CHABACTEE OF OEUDE SEWAGE. 113

parts per million, representing 19 per cent of sea water, while between 

these maxima there are minimum points of about 200 parts per million, representing only 1 per cent of sea water. It may be an important question in any project for the purification of Boston's sewage 

whether the extra cost of pumping and of treating this sea water 

might not be greater than the cost of keeping it out of the sewers. 

On the other hand, there is the possibility that this large amount of 

sea water, saturated as it is with oxygen, may be of actual advantage 

in any aerobic process of treatment.

With regard to the-variations in strength at different periods, the 

first point of importance to be noticed is the slight falling off in the 

strength of the sewage during the second year as compared with the 

first. This effect may probably be attributed to the fact previously 

mentioned (p. 98) that on October 14, 1904, the sewage of the upper 

part of the drainage system was diverted to the new high-level sewer. 

Much of this upper drainage area is sewered on the separate system, 

and ground water is in the main excluded. Furthermore, even with 

the combined system, the relative amounts of rain water entering the 

sewer is much greater in the city of Boston, with its great area of 

paved streets, than in smaller places with more open spaces and 

smaller relative amounts of pavement. It might also be possible, 

with the increasing per capita water consumption noticed in all cities 

from year to year and amounting in the metropolitan water district to 

2 or 3 per cent per annum, that there would be a resulting decrease in 

the strength of the sewage. On the other hand, the low rainfall during 1905 must have operated in an opposite direction.

The quarterly variations in the strength of the sewage are considerable, and, as is shown on pages 122-123, markedly influence the effluents of the various purifying processes. The controlling cause in 

these seasonal variations is the rainfall. The first effect of a shower 

is to increase the oxygen consumed by the introduction of street washings. A long period of rain, however, has the opposite result. The 

general rule, as has been, stated elsewhere (Winslow and Phelps, 

1905), is that sewage is weakest in spring and summer. The precipitation was unusually low in the summer of 1904 and the spring of 

1905, and therefore the seasonal relations for the second year are 

somewhat abnormal.

IBE 185 W 8
114 THE PUKIFICATION OF BOSTON SEWAGE.

TABLE LVI. Composition of Boston sewage (quarterly averages'), 1903-1905.

^)ate.

September to November, 1903 . . 

December, 1903, to February, 

1904. 

March to May, 1904. ............

September to November, 1904 . . 

December, 1904, to February, 

1905. 

March to May, 1905. ............

June, 1903, to June, 1904 a ......

June, 1904, to June, 1905 a ......

June, 1903, to June, 1905 a ......

of samples. Number 

?7

42 

10

47 

33

44

35 

102 

153

255

F.). (° Temperature 

67

62 

51

69 

61

47

45 

60 

58 

59

Analyses (parts per million).

k. fj

S 

 P H

.....

330 

300 

300

300

"365' 

305

Nitrogen asAlbuminoid 

ammon'a.

Total.

7.4 

6.2 

6.6

5.4 

6.7 

5.4 

5

5.6 

6.3 

5.7 

5.9

In solution.

3.4 

3.1 

3.6

2.7 

3 

2.6 

3.1

3.1 

3.1 

3 

3

In 

suspension.

4 

3.1 

3

2.7 

3.7 

2.8 

1.9

2.5 

3.2 

2.7 

2.9

<s 'a

O

S

S

OS

Q

1

20.7 

21.3

24

15.3 

21

18.4 

14

17.2 

19.7 

17.6 

18.5

'C 

+j

2

0.11 

.41

.42

.14 

.16 

.22 

.10

.08

!l4 

.19

Of

03 s-i +3 %

0.1 

0 

0

0 

.2 

.4 

.2

0 

.1 

.1 

.1

Oxygen 

consumed.

Total.

46 

48.7 

49.6

38.7 

41.9 

40.2 

38.6

47.4 

45.2 

41.5 

43.1

Soluble.

22.5 

23.7 

22.2 

25.7

27.3 

22.5 

24.6 

23.8

 d 

j> "o

 3

§

S

« 

o

2.4

4.2

2.3 

.3 

.9 

4.2

3.6 

2.8 

2.2 

2

a Yearly and biyearly averages given in this and subsequent tables are obtained by averaging the 

daily results and are therefore not averages of the quarterly figures given.

REMOVAL OF SUSPENDED MATTER.

In any discussion of the solids in sewage it is necessary to distinguish 

clearly between three classes of suspended matter. In the first place, 

there are generally present large floating objects, such as rags, paper, 

sticks, and other gross debris. Before pumping sewage it is customary to pass it through screens for the separation of such material, 

which may therefore be denoted as screenings. Another class of 

matter, present especially in sewage which includes street washings, 

consists of sand and other heavy mineral particles, sharply distinguished from the ordinary sewage sludge by the rapidity with which 

they settle out when the sewage is brought either to complete rest or 

to a low velocity of flow. Chambers or tanks for the removal of such 

material are commonly called grit chambers or detritus tanks, and the 

material may be conveniently spoken of as detritus. After the 

removal of the screenings and the detritus there remains in suspension 

the sewage sludge proper, composed of finely divided matter largely 

organic in nature which settles out only at a low velocity, and then 

but slowly.

As a rule it is found desirable to screen sewage which is to be 

pumped and to settle sewage which has to pass through an inverted 

siphon, as is the case with that of the south metropolitan district. 

Where any purification is to be carried out both these preliminary 

treatments are generally advisable. The amount of solid material 

removed is often considerable. At Manchester, England, during 1904, 

the amount of combined screenings and detritus amounted to about 

4,000 tons from a total of 13 billion gallons of sewage, or about 7,000 

pounds per million gallons (Manchester, 1904). At Boston during
REMOVAL OF SUSPENDED MATTER. 115

1903 about 10,000 cubic yards of detritus were removed from the settling chamber at the Dorchester pumping station from a total volume 

of sewage of 32 billion gallons, an average of about 0.31 cubic yard 

per million gallons. The composition of this detritus is not known, 

but a fair estimate would be 60 per cent of water and a solid content 

of 14 tons per yard, making 900 pounds per million gallons of sewage 

(Boston, 1904). The amount of screenings removed during 1897 was 

recorded and found to be about 1,000 cubic yards, or, roughly, 500 tons, 

an average of 300 pounds per million gallons of sewage (Boston, 1898).

In the experiments at this station, as noted above, screenings and 

detritus were taken out by a grit chamber and to a slight extent by 

supply tank A. During the actual time of pumping the pump discharges on an average about 1,000 gallons per hour, which produces a 

velocity of 1.1 feet per second in the 2J-inch suction pipe. The 

velocity is checked in the grit chamber, being reduced to an average 

of 0.04 foot per second, and the time occupied in passing the grit 

chamber is about forty-five seconds. Since March, 1904, when the 

grit chamber was installed, a careful record of the amount of sedimentremoved has been kept, the whole amount carefully sampled, and an 

aliquot portion preserved for analysis. A small amount of material 

removed from supply tank A has also been weighed and sampled and 

mixed with the grit chamber material in proportionate parts.

The amount of detritus removed by the grit chamber amounted in 

sixteen months to 4,800 pounds, or 2.4 cubic yards, of wet material 

from a total volume of sewage equal to a little over 3 million gallons 

1,600 pounds, or 0.65 cubic yard per million gallons. All the material 

thus removed was carefully sampled and its moisture determined. A 

portion of each dried sample was preserved and mixed with proportionate parts of later samples, and the mixture was finally analyzed. 

A certain portion of each sample, consisting largely of clean stone, 

was not included in the analysis. The amount of moisture, the proportions of clean stone and of dry detritus, and the analysis of the 

latter are shown in Table LVII, first in total amounts and then in 

parts per million of the total volume of sewage (3 million gallons).

TABLE LVII. Amount and composition of detritus removed from grit chamber from March

26, 1904, to June 1, 1905.

Pounds per million gallons of

Parts per million parts of sewWet detritus.

4,800 

1,600 

190

Water.

1,300 

430 

52

Clean 

stone, 

etc.

570 

190 

23

Fine, dry detritus.

Total.

2,900 

970 

117

Loss on 

ignition.

319 

106 

13

Organic 

nitrogen .

6.6 

2.2 

.26

Organic 

carbon by permanganate.

5.1 

1.7

.2
116 THE PtJRIFICATION OF BOSTON SEWAGE.

As the analysis indicates, this material is not sludge in any sense of 

the word. It is for the most part clean sand mixed with a considerable amount of coal cinders and small bits of wood, cloth, and pebbles. During the whole period it has been spread upon the grounds 

of the station immediately surrounding the laboratory and has given 

no offense.

The figures show only the total and average amounts of detritus 

collected for the whole period. No accurate data are at hand to show 

the effect of the seasons on the amount of detritus deposited It 

may be judged by the frequency with which it was necessary to clean 

out the chamber that the maximum deposits occurred during the 

early spring thaws. The Boston city records, already referred to/ 

show that at Moon Island there is a maximum of deposit in March 

and a second maximum during the summer months. Local conditions of rainfall evidently largely determine the amount of detritus 

sent into the sewer, but monthly variations from the mean yearly 

deposit are not as a rule greater than 25 per cent of that value. In the 

'spring of 1904 a large amount of snow was thawed by the warm rains 

and during ten days 1,600 pounds of detritus were taken from the 

detritus chamber and from storage tank A, into which some excess of 

detritus had been carried over; this was about one-third of the total 

amount removed during the fifteen months of the experiment. The 

amount of sewage pumped during that time was 100,000 gallons, giving an average of 16,000 pounds of detritus per million gallons of sewage. This may be fairly taken as the maximum for a like period of 

time, although for shorter periods the rate of deposit might be greater.

The line of demarcation between the so-called detritus and the 

remaining suspended solids, or sewage sludge proper, is rather sharply 

marked by the rapidity with which the particles settle. One class of 

material will settle out in a very few minutes when the velocity is still 

considerable and the other will settle only when the liquid is practically at rest and in the course of hours rather than minutes. According to figures given by Robinson (1896), a velocity of 0.5 foot per second will not move fine clay and 0.7 foot will just move coarse sand. 

Hence it may be stated that detritus may be removed from sewage at 

any velocity less than the former figure. On the other hand, sedimentation of the true suspended sludge necessitates a slackening of velocity to 0.1 foot per second or less. In the London settling basins velocities of 0.07 foot are maintained; at Manchester, 0.05; at Saltley and 

Sutton, 0.03; and at Frankfurt a. M., 0.01 to 0.02. Steurnagel (1904) 

found that velocities less than 0.07 foot permitted as complete sedimentation as was possible with absolute rest, but that 0.13 foot was 

too great-. Again, the time required for sedimentation is considerably 

different in these two classes of material. Detritus, being largely 

sand, will settle out in a very few minutes; but the remaining solids
REMOVAL OF SUSPENDED MATTfiB. 117

require a much longer time for sedimentation. In some experiments 

on this point in a 40-cm. cylinder the removal.of suspended solids by 

sedimentation was found to be about 25 per cent in five minutes, 50 

per cent in thirty minutes, and 75 per cent in twenty-four hours. 

Steurnagel studied the same phenomenon in a deeper layer (2 meters) 

and found the removal of suspended organic matter to be 42 per cent 

in five minutes, 61 per cent in twenty-five minutes, 75 per cent in six 

hours, and 80 per cent in twenty-four hours.

Whether the suspended organic solids in sewage must be removed 

by some special process depends largely on the general method of purification. With intermittent filters, if there be ample areas of sand 

available, crude sewage may be handled without preliminary treatment, as is the case at most of the Massachusetts areas. When, on the 

other hand, suitable sand is difficult to obtain, it may be advisable to 

remove the suspended solids as far as possible in order to obtain more 

rapid rates. With the contact filter it seems probable that some 

method of sludge removal will be generally necessary in order to maintain the capacity of the beds. With the trickling filter it may often 

be possible to handle crude sewage without preliminary treatment. 

If a clear, as well as a nitrified, effluent is desired, however, sedimentation must follow the oxidizing process. Whether the removal of solids 

should precede or follow filtration in this case must be determined by 

experiment.

If the organic suspended solids are to be removed from, sewage, 

there is a choice of three different methods namely, sedimentation, 

chemical precipitation, and straining. For a comparison of the three 

methods, experiments at Lawrence furnish some useful data. Table 

LVIII has been compiled from the annual reports of the Massachusetts 

State board of health for the years 1893-1903.

TABLE LVIII. Effect of various processes of preliminary sewage treatment at Lawrence, 

Mass. (Massachusetts, 189Jf-190J£).

[Parts per million.]

Process and material.

Alum precipitation:

Effluent ......................

Hard-coal strainer: 

Sewage .......................

Effluent ......................

Coke strainer:

Septic tank A : 

Sewage .......................

Sedimentation : 

Sewage .......................

Date.

\ 1893-1897. ........

1 June, 1894, to Sep- 

| tember, 1898.

Nitrogen as 

Albuminoid ammonia.

Total.

f 6.3

I 2.8

f 5.5 

I 3

f 6.4 

\ 3.3

f 6.4 

1 3.3

1 6.3 

I 4.2

In solution.

2.6 

2

2.9 

2.1

2.5 

2.3

2.9 

2.1

2.6 

2.7

In suspension.

3.7

.8

2.6 

.9

3.9 

1

3.5 

1.2

3.7 

1.5

Free ammonia.

29.7 

30.7

42.1 

43.3

30.8 

31.8

39.1 

36.7

29.7 

33

Oxygen 

consumed in 2 minutes' 

boiling.

40.3 

20.9

38.1 

23.6

38.8 

22.2

47.7 

29.4

40.3 

30.7
118 THE PiraiPICATlON OF BOSTON SEWAGE.

The samples of effluent from, chemical precipitation with alum 

represent the supernatant liquor obtained by treating the sewage 

with sulphate of alumina at a rate of 1,000 pounds per million gallons 

and allowing the mixture to settle for four hours in a barrel. The 

sedimentation experiments were made by settling the sewage for four 

hours without other treatment. The coke strainer was a layer of coke 

breeze 6 to 8 inches deep and was operated at a rate of about 1 million 

gallons per acre per day. The coal strainer was a 12-inch layer of 

"buckwheat" coal and was run at a rate of approximately 1 million 

gallons per acre per day. Some septic-tank results for 1900-1903 have 

been included, the septic tank being considered in this place as a 

variant of sedimentation. The important conclusion from these 

experiments is that the results of the various processes are not very 

dissimilar. The small differences observed are in favor of the chemical-precipitation process, plain sedimentation showing the poorest 

results.

Martin (1905) has compiled, from the testimony given before the 

royal sewage commission, figures from various sources relating to the 

removal of suspended solids by chemical precipitation, septic tanks, 

and coarse filters. While the coarse filter is not strictly a preliminary 

treatment for the removal of suspended solids, since it is also a true 

process of purification, the comparative results obtained by these 

three processes are of interest in this connection. The average suspended solids in effluents from chemical precipitation plants are, at 

Kingston 14 parts per million, at Chorley and Richmond from 40 to 

70, and at London 112. Similar figures from septic-tank installations are, at Salford 29 to 71, Manchester 100 to 286, Leeds 114 to 143, 

Burnley 130, Oldham 143, Sheffield 157, Accrington 178, and Birmingham 244. The average suspended solids in coarse-bed effluents 

are at Sheffield 43 to 57, Sutton 45, Blackburn 60, Aylesbury 111, and 

Leeds 151 to 196.

In general it is clear that chemical precipitation and straining will 

produce effluents which as regards suspended solids only are somewhat 

superior to those from either plain sedimentation or septic treatment. 

In the case of precipitation the cost of the chemical treatment and the 

necessary disposal of an increased volume of sludge must be considered. In straining processes sludge is produced in varying quantity 

according to the conditions under which the strainer is operated. A 

strainer run at so low a rate that anaerobic processes are carried out 

within it is practically a septic tank and can be so operated that there 

is little accumulation of organic matter. Such a strainer is septic 

tank No. 6 at this station, described on page 124, where it is pointed 

out that here the tank operates like a simple septic tank, the stone 

filling playing no important part. Again, with still lower rates and
TREATMENT IN SEPTIC TANK. 119

with resting periods, the strainer becomes practically an oxidizing 

filter and disposes of considerable sludge in much the same way as does 

a contact bed. On the other hand, true strainers, run at rapid rates 

with the object simply to remove suspended solids without destroying 

them, come in a different class. Their surfaces require constant care, 

while not only the accumulated sludge itself but that part of the surface which is necessarily removed at the same time must be disposed 

of. Sedimentation, although it does not give quite such perfect 

removal, is generally preferable to either of these methods, since it 

avoids the expense of chemicals and of renewing or treating the surface of strainer beds; it will probably prove in general the most practical and economical process of preliminary treatment for removing 

fine suspended material.

Under the term sedimentation is included septic treatment, since 

the septic process is really plain sedimentation with the additional 

anaerobic fermentation of the sludge produced. Such a process 

seems to combine the best features of all the preliminary treatments 

thus far proposed, since it effects an adequate removal of suspended 

solids with no expense for chemicals and produces a minimum of 

sludge. Furthermore, the actual removal of suspended solids is 

somewhat greater with the septic tank than with plain sedimentation, 

from the solution of particles too small to settle easily. The only disadvantage in septic treatment is that if it be too prolonged changes 

may be set up which make subsequent treatment difficult. The 

problem is to combine the maximum liquefying action with the 

minimum production of toxic substances. If that can be done, the 

septic tank offers in general the best solution of the problem.

PRELIMINARY TREATMENT IN THE SEPTIC TANK.

It having been assumed that if any preliminary treatment were 

necessary in the purification of Boston sewage the septic tank would 

probably furnish the most available method, the next problem was 

to determine the best conditions under which a septic tank could be 

operated. In particular, it was desired to compare the efficiency of 

different periods of storage, the results obtained from open and 

closed tanks, and the effect of filling a tank with stone in order to 

increase the amount of surface action.

Tanks Nos. 5, 6, 8, and 10, all closed tanks, were started in June, 

1903, and open tanks Nos. 7 and 9 in March, 1904. All were operated continuously until June, 1905. Tank No. 5 was operated for 

the first six months at a forty-eight hour rate and for the remaining 

eighteen months at a twelve-hour rate. Tank No. 7 had a twelvehour period, tanks Nos. 6, 9, and 10 a twenty-four hour period, and
120 THE PUBLICATION OF BOSTON SEWAGE.

tank No. 8 a forty-eight hour period. In each case the linear distance traveled was about 6 feet and the depth 3 feet, making the

/903.

 Szw: ate.

QUARTER-YEAR ENDING

I9O4 

JUNC SEPT. DEC.

\

SUSM VDfO ALBUMINOID AMMONIt

V

CONSUMED

. TANK 5 .TANK 7

__.___TANK 6 +__ +TANK 8 _____-TANK 10 

FIG. 16. Composition of septic effluents.

. SEWAGE

ratio of l:d equal 2:1. The importance of this factor has recently 

been pointed out by Hazen (1904). Tank No. 6 was filled with
TREATMENT Itf SEWiO TANK. 121

1^-inch crushed stone. Septic action began in all the tanks very 

soon after they were started, the effluent being free from gross turbidity and much darkened. The dark color and offensive odor of 

these septic effluents are undoubtedly due in part to the formation 

of sulphides from the large amount of sulphates introduced with the 

sea water. This phenomenon has been noticed by Clark in the 

treatment of hard waters at Lawrence (Barbour, 1904). HoppeSeyler (1886) believed the reaction to be a direct reduction of calcium sulphate by methane. It is of some importance, aside from 

the foul odors produced, since it has been found at Burton-uponTrent that the formation of H2S has a serious effect on subsequent 

purification on land (Smith, 1901). Scum formed at first on the 

open tanks, but later disintegrated and sank and did not re-form. 

In the closed tanks a scum 1 inch thick was found when they were 

finally opened.

The most important constituents of the effluents from the various 

tanks are plotted in fig. 16. It will be noticed in the first place that 

the various effluents are much alike in composition. All show a 

general improvement during the course of the two years, but this 

is accounted for rather by the decreasing strength of the sewage 

than by increased efficiency. The septic-effluent curves follow the 

crude sewage closely all through, rising in the late autumn of 1903, 

in the summer of 1904, and in the spring of 1905, when the sewage 

strengthened with diminishing rainfall. In absolute values, oxygen 

consumed shows a slight decrease in the septic tanks and free ammonia a slight increase. No doubt the reduction in carbonaceous matter is really considerably greater than it appears, since the septic 

decomposition temis to break up the more stable compounds and 

increases that proportion of the total carbonaceous matter which is 

revealed by the oxygen-consumed test. The hydrogen sulphide also 

interferes seriously with the value of this test. The chief difference 

between the sewage and septic effluents, aside from the reduction 

in turbidity, appears in the albuminoid ammonia. The nitrogen in 

this form was diminished to from two-thirds to one-half its sewage

value. The diminution of dissolved albuminoid ammonia was slight * . ' . 

but distinct, while the suspended portion was reduced to a little

over one-third its original amount. The suspended albuminoid 

ammonia is plotted with the total oxygen consumed and free ammonia in fig. 16.
122 THE PURIFICATION OF BOSTON SEWAGE.

TABLE LIX. Quarterly averages of analyses of effluent from septic tanks. 

TANK 5, CLOSED TANK; STORAGE PERIOD, TWELVE HOURS." ,

Date.

1903-4.

1904-5.

December to February. ............

Temperature 

(°P.)-

68 

59

48 

52 

58

67 

57 

44 

46 

56 

57

Analyses (parts per million).

Turbidity.

240 

240

220 

190 

190 

200 

200 

200

Nitrogen as 

Albuminoid ammonia.

Total.

4.2 

3.1

3.9 

6 

4.1

3.8 

3.6 

3.6 

3.2 

3.6 

3.8

In solution.

2 

2.4 

2.9 

2.8 

2.6

2.7 

2.b 

2.8 

2.6 

2.7 

2.6

In suspension.

1.6

.7 

1 

3.2 

1.5

1.1 

1 

.8 

.6 

.9 

1.2

Free 

ammonia.

22.9 

25 

34.2 

19 

24.3

18.7 

19.6 

14.6 

19.7 

18.1 

20.7

Oxygen consumed.

Total.

38 

45.9 

41.3 

36.5 

41.7

30.1 

42.1 

28.9 

33 

33.2 

36.9

T>'ssolved.

26.5 

26.5

23.8 

34.3 

22.9 

28.1 

26.9 

26.9

TANK 6. CLOSED SEPTIC TANK FILLED WITH STONE; STORAGE PERIOD, TWENTYFOUR HOURS.

1903-4.

1904-5.

68

CQ

47

52

58

67

59

44

46

54

57

180

170

190

190

160

180

180

3.7

2.9

3.6

4.1

3.4

3.2

3.3

3.9

3.3

3.4

3.4

2.6

2.2

2.6

2.9

2.5

2.2

2.5

3.2

2.4

2.6

2.5

1.1

.7

1

1.2

.9

1

.8

.7

.9

.8

Q

23.5

26.5

34.2

16

24.3

21.9

19.6

15.7

20.8

19.5

21.5

42.8

50.3

42.7

37

44.9

32.4

34

29.6

33.3

32.2

37.8

26.2

26.2

27.2

29.7

22.8

24.7

26

26

TANK 7, OPEN SEPTIC TANK; STORAGE PERIOD, TWELVE HOURS.

1904-5.

Yearly average, June to June. .

52

69

45

46

56 

55

170

160

170

180

190

170 

170

3.9

2.8

3.1

3.5

3.7

3.2 

3.4

2.5

1.7

2.3

3

3.1

2.5 

2.5

1.4

1.1

.8

.5

.6

.7 

.9

16.5

20.3

20. 1

14.5

16.8

17.9 

17.6

33.1

35.8

34.9

27.7

35.5

33.2 

33.2

26.5

31.4

31.7

21.4

29

28.1 

27.9

TANK 8, CLOSED SEPTIC TANK; STORAGE PERIOD, FORTY-EIGHT HOURS.

1903-4.

1904-5.

58

47

51

57

67

38

45

56

57

230

230

200

210

180

170

190

190

5.6

3.6

5

4.3

4.3

3.7

3.5

3.7

3.5

3.6

3.8

2.5

2.1

3.3

2.3

2.4

2.3

2.5

3.1

2.8

2.7

2.6

3.1 1.5

1.7

2

1.9

1.4

1

.6

.7

.9

1.2

22.4

26.8

35

16.1

25.1

19.5

23.5

15.3

23

20.5

22.1

42.4

52.3

47.7

32.8

46.1

32.9

42.9

31.6

41.6

37.3

40.7

26.5

26.5

26.3

35.6

25.1

33.8

30.3

29.9

a Before Dec. 7, 1903, 48 hours.
TREATMENT IN SEPTIC TANK.

TABLE LIX. Quarterly averages of analyses of effluent from septic tanks Continued. 

TANK 9, OPflN SEPTIC TANK; STORAGE'PERIOD, TWENTY-FOUR HOURS.

Date.

1904-5.

Yearly average, June to June. .

Temperature

(° F.).

52 

68 

55 

45 

46 

56 

55

Analyses (parts per million).

Turbidity.

170 

160 

170 

190 

ICO 

170 

170

Nitrogen as 

Albuminoid ammonia.

Total.

3.6 

2.7 

2.9 

3.6 

3.9 

3.2 

3.2

In solution.

2.4 

1.8 

2.2 

2.9 

3.2 

2.4 

2.4

In suspension.

!g

.7 

.7 

.7 

.8 

.8

Free 

ammonia.

18.6 

22.9 

21.2 

15.3 

18.8 

19.6 

19.4

Oxygen consumed.

Total.

36 

36.9 

36.3 

27.3 

36 

33.7 

34.1

Dissolved.

26.6 

29.1 

32.1 

21.9 

29.8 

27.7 

27.5

TANK 10, CLOSED SEPTIC TANK; STORAGE PERIOD, TWENTY-FOUR HOURS.

1903-4.

1904-5.

66 

58 

49 

51 

57

67 

57 

43 

45 

56 

56

270 

270

190 

220 

250 

170 

210 

210

4.5 

3.4 

3.8 

4.2 

3.8

3.5 

3.9 

3.9 

3.7 

3.7 

3.8

2.6 

2.1 

2.9 

2.4 

2.4

1.9 

2.8 

3.2 

2.7 

2.6 

2.5

1.9 

1.3 

.9 

1.8 

1.4

1.6 

1.1 

.7 

1 

1.1 

1.3

21.3 

24.3 

35 

18.2 

23.4

24.6 

24.4 

18.1 

20.8 

21.9 

22.5

34.3 

38.5 

48 

34.6 

37.9

41.3 

34 

36.3 

36.3 

37.3 

37.5

26.4 

26.4

23.2 

23 

23.6 

27.5 

24.1 

24.5

TABT.E LX. General averages of analyses of crude sewage and septic effluents.

Material.

Do.....................

Effluent from tank No. 5 ...

Effluent from tank No. 7 ... 

Effluent from tank No. 8 ... 

Effluent from tank No. 9 ... 

Effluent from tank No. 10. .

Date.

June, 1903, to

June, 1905. 

March, 1904, 

to June, 1905. 

June, 1903, to 

June, 1905. 

.....do........

March, 1904, 

to June, 1905. 

June, 1903, to 

June, 1905. 

March, 1904, 

to June, 1905. 

June, 1903, to 

June, 1905.

Storage 

period 

(hrs.).

048-12

24 

12

48 

24 

24

Temperature

(°F.).

59 

58 

57

57 

55

57 

55 

56

Analyses (parts per million).

Turbidity.

305 

305 

200

175 

170

190 

170 

210

Nitrogen as 

Albuminoid ammonia.

Total.

5.9 

5.7 

3.8

3.4 

3.4

3.8 

3.2 

3.8

In 

solution.

2.6

2.5 

2.5

2.6 

2.4 

2.5

In 

suspension.

2.9 

2. 7 

1.2

.9 

.9

1.2 

.8 

1.3

Free 

ammonia.

18.5 

17.6 

20.7

21.5 

17.6

22.1 

19.4 

22.5

Oxygen 

consumed.

Total.

43.1 

41.5 

36.9

37.8 

33.2

40.7 

34.1 

37.5

Soluble.

24.4 

24.7 

26.9

26 

27.9

29.9 

27.5 

24.5

Changed Dec. 7, 1903, from 48 hours to 12 hours.
124 THE PURIFICATION OF BOSTON SEWAGE.

The average analyses- of the effluent from-each tank for the whole 

period of operation, with the average analyses of the k sewage for the 

fifteen-month and the two-year periods, are indicated in Table LX. 

The figures on the whole show a remarkable uniformity of results for 

open and closed tanks and for twelve, twenty-four, and forty-eight 

hour periods. Even the figures for suspended albuminoid ammonia 

and total oxygen consumed bring out only slight differences. In a 

comparison of tanks Nos. 5 and 10 (closed) with the corresponding 

twelve and twenty-four hour open tanks, the open-tank effluents 

appear to be slightly better. It must be remembered, however, that 

the open tanks were operated during the last fifteen months only, 

when the sewage was weaker. This factor being taken into account, 

the work of the open and closed tanks is practically equal.

With regard to period the figures are no more conclusive. A comparison of tanks Nos. 7 and 9 (open) apparently shows no important 

difference between the effect of twelve and of twenty-four hours' 

storage. Similarly, tanks Nos. 5, 8, and 10 (closed) produce almost 

the same results, although operating with periods varying from 

twelve to forty-eight hours. Tank No. 6, filled with IJ-inch crushed 

stone, produces a somewhat greater reduction in suspended albuminoid ammonia than do the other tanks, but the difference is too slight 

to be of practical importance.

TABLE LXI. Analyses of septic-tank contents, including sludge and scum, at dose of

experiment.

No. of 

tank.

5...... 

6......

7......

8. ._..." 

9...... 

10.....

Date.

June, 1903, to 

June, 1905. 

.....do............

March, 1904, to 

June, 1905. 

June, 1903, to 

June, 1905. 

March, 1904, to 

June, 1905. 

June, 1903, to 

June, 1905.

Storage 

period 

(hrs.).

«48-12 

24

12 

48 

24 

24

Depth 

of 

sludge 

(in.).

8.4

3.3

8.7 

4.4 

5.4

Analyses (parts per million).

Solids.

Total.

17,000

10,600 

14,900 

12,500 

16,900

Loss 

on ignition.

6,580

3,040 

6,068 

3,912 

5,952

Nitrogen asFree 

ammonia.

35

6 

34

50 

40 

50

Albuminoid ammonia.

Total.

145

66 

42

80 

70 

102

Soluble.

10

10 

10

10

7

Total.

425

250 

400 

325 

400

Oxygen 

consumed.

Total.

1,000

640 

680

940 

680 

1,020

Soluble.

130

48 

100

110 

110 

100

Fats.

1,590

3,008 

620

870 

1,090 

900

o Changed Dec. 7, 1903, from 48 hours to-12 hours.

When this series of experiments was closed in June, 1905, the inlet 

and outlet of each tank were closed and the contents, including scum 

and sludge, were thoroughly stirred. Samples of the suspension thus 

produced were then analyzed in order to gain an idea of the material 

which had accumulated during the whole period of operation. The 

results are shown in Table LXI. The analyses refer to the total
TBEATMENT IN" SEPTIC TANK. 125

liquid and solid contents of the tank at the time its operation ceased, 

a suspension containing about 98 per cent of water. The sludge was 

estimated by allowing the mixed tank contents to settle in a cylinder 

for twenty-four hours and observing the relation between the 

thick sediment produced and the clear supernatant liquid. The 

thickness of the sludge (which as measured by this method includes 

the scum also) was 3.3 and 4.4 inches for the tanks which had run for 

fifteen months and 5.4, 8.4, and 8.7 inches for those which had run for 

two years. With regard to total solids the loss on ignition is important and measures fairly the total storage of organic matter by the 

septic tank. This is seen to be from 3,000 to 4,000 parts per million 

after fifteen months and about 6,000 parts after two years. The effect 

of the storage period on the accumulation of sludge is striking. As 

already shown, the tanks in which the flow was more rapid appear to 

exercise quite as much purifying power as the slower ones. Since 

twice as much sewage passed through tank No. 7 as through tank No. 

9 and twice as much through tank No. 10 as through tank No. 8, with 

the production of a comparable effluent, more sludge might be expected 

in tanks Nos. 7 and 10. We actually find less, which suggests that the 

decomposing action of the tank is favored by a shorter storage period. 

In tank No. 7, with a twelve-hour period, there were 3.3 inches of 

sludge, corresponding to 0.6 cubic yard per million gallons of sewage 

passed. In tanks Nos. 5, 9, and 10, with a twenty-four-hour period, 

the depth of sludge was respectively 8.4, 4.4, and 5.4 inches, equivalent to 1.4, 1.7, and 1.5 cubic yards per million gallons. In tank No. 

8, with a forty-eight hour period, there were 8.7 inches of sludge, or 

4.7 cubic yards per million gallons.

It has been pointed out above that a prolonged septic action diminishes the number of bacteria and probably interferes with.sludge 

reduction. Another interesting suggestion, which may help to 

explain the results herein recorded, has recently been made by Stoddart (1905). He finds, in a septic tank of several compartments, a 

considerable deposit of sludge in the first compartment, giving a. 

fairly clear supernatant liquid, which in the last chamber of all undergoes a secondary decomposition, leading to the throwing down of an 

additional precipitate of offensive sludge.

From the data in Tables LX and LXI have been calculated, in 

Table LXII, the actual amounts of certain constituents, which were 

(a) allowed to enter the tanks, (b) discharged in the effluents, (c) 

stored in the tanks as sludge and scum, and (d) removed by septic 

decomposition. About 50 pounds of nitrogen as albuminoid ammonia per million gallons of sewage entered the tanks. Roughly, 30 

pounds were discharged and 20 pounds remained behind, of which 

15 to 17 pounds were decomposed. The last columns in the table 

show the total volatile solids and fats stored in the various tanks,
126 THE PUEIFICATION OF BOSTON SEWAGE.

calculated in relation to the sewage treated. These figures bring 

out very sharply the superior decomposing power of the tanks operated at short periods/ Tank No. 7 (twelve hours) and tank No. 5 

(twelve Lours for the last eighteen months) exhibit the lowest values. 

Tanks Nos. 9 and 10 (twenty-four-hour period) come next, with 90 

and 101 pounds, respectively. Tank No. 8, with its forty-eight-hour 

storage, gave 206 pounds of stored organic matter per million gallons 

of sewage treated. The large proportion of fats shown in the last 

column is notable, amounting to one-fourth or one-eighth of the 

total stored organic matter.

TABLE LXII. Storage and decomposition of organic matter in septic tanks.

No. of 

tank.

a .....

6.....

7 .....

8.....

9.....

10 .....

Flow 

(gallons) .

445,000

135,000

393, 000

133,000

197,000

266,000

Storage 

period 

(hours) .

«48-12

12

48

24

24

Nitrogen as 'albuminoid ammonia .

Entering, 

(a.)

Leaving 

(6.)

Stored, 

(c.)

Decomposed. 

(d=a b c.)

Solids stored.

Total. Loss on 

ignition.

stored.

Pounds per million gallons of sewage passed.

49.2

46.7

49.2

46.7

49.2

31.7

28.3

31.7

26.7

31.7

1.3

610.1

.4

2.6

1.5

1-6

16.9

11.9

18.1

15.9

17.8

17.3

178

115

510

279

282

69

35

206

90

101

16

101

6

29

25

15

« Changed December 7, 1903, from 48 hours to 12 hours.

& Estimated from loss of capacity in tank due to sludging up of the space between the stones and from 

analysis of a sample of the sludge.

Altogether it may be concluded from these experiments that the 

septic tank will effect a considerable removal of solids from Boston 

sewage, amounting to about two-fifths of the nitrogen as measured 

by albuminoid ammonia. Its effluent is free from gross turbidity, 

but dark and offensive from the liberation of hydrogen sulphide. 

Of the organic matter retained in the tank, a very large proportion, 

amounting to well over three-fourths if measured by the albuminoid 

nitrogen, is decomposed, and the accumulation of store.d material in 

the tank is slight after two years of operation. Apparently such 

tanks might operate for several years without being cleaned. The 

covering of tanks is nonessential, since closed and open tanks work 

equally well. Storage periods varying from twelve to forty-eight 

hours give similar effluents, but there is an increasing tendency to 

accumulate sludge as the period is lengthened. The filling of a 

septic tank with stone is of only slight advantage.

It is believed, therefore, that open tanks with a capacity not exceeding the flow for twelve hours would prove the most favorable preliminary treatment for Boston sewage.

PURIFICATION BY INTERMITTENT SAND FILTRATION.

The early Lawrence experiments indicated pretty clearly what 

may be effected by intermittent sand filters operating under the 

most favorable conditions. They showed that a 4 to 5 foot bed
INTEBMLTTENT SAND FILTRATION. 127

of sand of an effective size of 0.04 to 1.4 mm. would take sewage at 

rates varying from 0.02 to 0.06 million gallons per acre per day, 

producing a clear and odorless effluent in which the nitrogenous constituents had been almost entirely converted into the mineral form. 

In the line of a modification of the process in order to secure more 

rapid rates than these the only important step has been the installation of preliminary septic tanks, and septic effluent has been treated 

in the Middle West at rates up to 0.4. Exact data are scarce, however, as to the comparative operation of sand filters with crude 

sewage and with septic effluent. It was therefore planned, in this 

investigation, to determine how far the preliminary septic process 

would be of advantage in the treatment of Boston sewage, and 

with or without its use to what extent the required area of sand 

could be diminished by the use of rates of filtration over 0.1 million 

gallons per acre per day. It was desired also to find out how far the 

depth of sand could be decreased with safety, since this may be an 

important economic consideration when artificial sand areas must be 

constructed.

The first sand filters, Nos. 1 and 2, began operation in June, 1903. 

Both were cypress, tanks, 6 by 4 feet by 3 feet deep, underdrained 

with 6 inches of material ranging from 3-inch stones up to the sand. 

No. 1 contained, over the underdrain material, two feet, and No. 2 one 

foot of drift sand with an effective size of 0.17 mm. and a uniformity 

coefficient of 3.5. Both were started at a rate of 0.1 and so operated 

until December, 1903. At that time the rate on No. 1 was doubled, 

while that of No. 2 remained the same in amount but was divided into 

two daily doses with twelve hours' interval between them. In June, 

1904, both rates were doubled, No. 2 receiving 0.2 million gallons per 

acre per day in two doses and No. 1 receiving 0.4 million gallons per 

day in four doses. Both filters received crude sewage.

This experiment gave conclusive results as to the minimum depth 

for a sand filter. While the 2-foot filter worked satisfactorily, No. 2, 

with half that depth, was a failure. Its effluent was dark and turbid 

and of an offensive odor. Not one of the samples tested passed the 

incubator test. The analytical results in Table LXIII show marked 

variations from time to time, but the free ammonia present was generally from 15 to 20 parts per million nearly as high a value as that 

of the crude sewage. The albuminoid ammonia was usually between 

2 and 3 parts and the oxygen consumed about 20 parts in each case 

about half the sewage value. Nitrates were always low.

The operation of the 2-foot bed, on the other hand, was eminently 

satisfactory. The effluent was clear and bright and entirely free from 

turbidity and odor. Every sample tested successfully passed the incubator test and even bacteriologically the effluent appeared well, having an average of 1,220 bacteria per cubic centimeter. The bacterial 

composition of the various effluents obtained in these experiments
128 THE PURIFICATION OF BOSTON SEWAGE.

has been fully discussed elsewhere (Winslow, 1905 a). The analytical 

characters of the effluent from tank No. 1 are given in Table LXIII. 

The free ammonia once reached 9 parts per million in the summer 

quarter of 1904, just after the increase in rate, but has been generally 

under 4 parts. The albuminoid nitrogen has been under 1 part, and 

the oxygen consumed under 8 parts except in one quarter. The nitrates, on the other hand, have not fallen below 20 parts, indicating 

a very high degree of purification, and dissolved oxygen has constantly been present. The increase in rate from 0.1 to 0.2, and again 

from 0.2 to 0.4, did not appreciably alter the quality of the effluent.

The surface of the filter, even at these high rates, has not required 

excessive care. It was scraped in August, 1903, and November, 1904, 

and raked once and scraped once in March, 1905. The total material 

removed in three scrapings during two years of operation amounted 

to a layer 0.48 inch thick, or 1,600 cubic inches. This is equivalent 

to 0.36 cubic yard per million gallons of sewage filtered.

Tanks Nos. 24 and 25 were put in operation in March, 1904, in order 

to compare the treatment of septic effluent with the purification of 

crude sewage as conducted in tank No. 1. All three were alike in construction. Tanks Nos. 24 and 25 were throughout operated at a rate of 

0.4 million gallons per acre per day, taking four daily doses at six-hour 

intervals. Tank No. 24 received the effluent from tank No. 7, which 

had been septicized for twelve hours; tank No. 25 that from tank No. 

9, which had been septicized for twenty-four hours. The analyses of 

the effluents from tanks Nos. 24 and 25 are shown in Table LXIII. 

In each of the three tanks studied the nitrates increased rapidly during the first months of operation (nine months in the case of tank No. 

25, six months in the other two cases) and then fell to a somewhat 

lower value.

Fig. 17 brings out more clearly the relative quality of the three 

effluents, showing that from tank No. 1, which took crude sewage, to be 

the best. In the figure the blocks for sewage constituents represent 

not the septic effluent applied, but the crude sewage before treatment. 

It will be noticed that the average sewage applied to tank No.l was 

stronger than that treated by septic tanks Nos. 7 and 9 and filters Nos. 

24 and 25. Nevertheless, the free and albuminoid ammonia values 

.are lower and the nitrates higher after sand filtration alone than after 

combined septic and sand.treatment.

In the condition of the surface, the filters receiving septic effluent 

showed a slight but distinct advantage. During fifteen months of 

operation tank No. 25 was raked over twice, in September, 1904, and 

March, 1905, but not scraped. Tank No. 24 was raked on the same 

dates and also scraped once in March, 1905. This scraping was rendered necessary by a rather unusual phenomenon, the deposition of a 

thin layer of finely divided sulphide of iron formed by decomposition.
INTERMITTENT SAND FILTRATION. 129

of sulphates in the septic tank. After one removal this layer did not 

again form. It is probable that experiments extending over a longer 

period might have shown greater advantages in the septic process in 

relation to the permanency of filtering surface.

TABLE LXIII. Quarterly averages of analyses of efficients from slow sand filters. 

TANK NO. 1, 2 FEET DEEP, TAKING CRUDE SEWAGE.

September to November, 

1904.......................

December, 1904, to Febru56 

67

54

41 

43 

52 

54

4

26

47

0 

8 

26 

19

.6

.8

.5

.4 

.8 

.6 

.6

2.9 

9! 3

3.5

3.8 

5.4 

5.4 

4.2

.48 

.27

.27

.34

.38 

.32 

.39

19.6 

26.8

22.3

24.7 

22 

23.9 

22.3

4.3

8.5

7.4

4.3 

7.2 

6.8 

5.6

5.3 

6

5.4

8.1 

5.6 

6.3 

6.1

TANK NO. 2, 1 FOOT DEEP, TAKING CRUDE SEWAGE.

September to November, 

1903.......................

December, 1903, to FebruMarch to May, 1904. ........

Yearly average . ......

September to November, 

1904.......................

December, 1904, to February, 1905 ..................

64 

54

40 

,54 

54 

67

56

42 

44 

54 

54

210 

350 

255 

110

165

165

45 

135 

170

0.2 

1.9

1.8 

2 

1.9 

2.5

3.5

3.5 

2.8 

3.2 

« 2.5

20 

19.4

25.3 

20.1 

17.6 

17.6

18.3

12.6 

16.5 

16.1 

16.9

0.18 

.31

0 

.01 

.20 

.55

.33

.23 

.57 

.36

.28

8.5 

3.1

0 

0 

4.6 

1.2

4.5

2.9 

2.3 

2.9 

3.5

11.6 

25.8

35.7 

17.7 

21.2 

17.9

25.6

28.3 

19 

23.7 

22.4

0 

0

0 

.2 

0 

0

3.5

. 1.9 

0 

1.8 

.9

TANK NO. 24, TAKING 12-HOUR SEPTIC EFFLUENT.

March to May, 1904. ........

June to August, 1904. .......

September to November, 

1904.......................

December, 1904, to FebruMarch to May, 1905.........

Yearly average, June 

1904, to June, 1905...

53 

68

52

42 

45

53 

53

18 

20

6

18 

8

15 

15

0 

5

0 

0

0 

0

1.6 

.5

.8

.7 

.6

.6

.8

10.4 

2.7

4.7

3.9

5

4 

5

0.25 

.60

.17

.14 

.29

.32 

.31

0.1 

19.2

28.5

17.9 

20

21.3 

19.9

6.8 

7.1

5.4

6.2 

7.1

6.5 

6.5

8.5 

6.6

8.5

8.8 

4.8

7.4 

7.5

TANK NO. 25, TAKING 24-HOUR SEPTIC EFFLUENT.

March to May, 1904.........

June to August, 1904. .......

September to November, 

1904.......................

December, 1904, to February, 1905 ..................

Yearly average, June 

1904, to June, 1905...

53 

68

53

42 

45

54 

54

18 

17

20

53

21

44 

43

0

5

0 

0

0 

0

1.6

.5

.9

.8 

.7

.7 

.9

10.5 

4.1

5.6

3.2 

7.3

4.9 

5.6

0.28 

.24

.10

.12 

.25

.18 

.19

1.5 

15.7

14.6

26.4 

18.4

18.8 

16

7.1 

6.2

7

4.3 

8.5

6.4 

6.5

4.7 

5

10.8

9.3 

3.4

7.5 

7.2

IEK 185 06 £
130 THE PURIFICATION OF BOSTON SEWAGE.

In general, the results obtained indicate that in reducing the depth 

of a sand filter it is not safe to go below 2 feet. One foot of sand is 

insufficient to effect purification, while a 2-foot bed may yield admirable results. With regard to the value of preliminary septic treatment of Boston sewage before sand filtration, it appears that effluents 

from the combined process are slightly inferior to those obtained by 

the sand process alone, while the care of the surface is more difficult 

when crude sewage is treated. These experiments, it is believed, suggest that it may be possible to treat crude sewage by sand filtration

Q

<!

u <\> ". > <!

EFF

u

PA

LUENT

1

FILTER

\

FI'LTER

\

FILTER

SEWA

NO. 1

N0.34

* 

N0.85

 > o J 

RTS PFR MIL 1

3E

J

J

y

OKI

w

FREE AMMONIA

ALBUMINOID AMMONIA 

NITRITES 

NITRATES

FREE AMMONIA

ALBUMINOID AMMONIA 

NITRITES

NITRATES

FREE AMMONIA

ALBUMINO D AMMONIA 

NITRITES 

NITRATES

8 8

FIG. 17. Comparison of various forms of nitrogen in crude sewage and sand-filter effluents.

at higher rates than have heretofore been recommended. The operation of filter beds under practical conditions is of course more difficult 

than in small-scale experiments. In the first place the distribution 

on large beds is often incomplete, while it is easy in small tanks to 

obtain perfect distribution. Again, the effect of winter weather was 

minimized in these experiments. It will be noticed in the tables that 

the quarterly temperature averages for the sand-filter effluents did 

not fall below 39° F. In order to estimate the actual importance of 

this point in outdoor filters, the ratios which the values of free and
INTERMITTENT SAND FILTRATION. 131

albuminoid ammonia, oxygen consumed, and nitrates for each month 

bear to the yearly average at Lawrence and Brockton have been calculated and are given in Table LXIV.

TABLE LXIV. Monthly variations in sand-filter effluents at Brockton and Lawrence, Mass.

[Yearly average= 100.] 

FREE AMMONIA.

Jan.

100

213

Feb.

163

269

Mar.

192

204

Apr.

171

168

May

134

84

June.

92

48

July.

79

16

Aug.

63

6

Sept.

50

8

Oct.

50

14

Nov.

50

32

Dee.

83

120

ALBUMINOID AMMONIA.

87

175

130

171

130 174

132

87

99

87

76

87

67

87

58

87

62

87

49

87

62

8" n r

NITRATES.

Brockton. 

Lawrence.

85 81

100

90

139

112

140

118

120

115

116

133

128

129

125

110

109

OXYGEN CONSUMED.

84

170

132

167

152

149

178

122

100

84

84

70

72

69

68

61

68

62

84

64

92

61

108

124

The Lawrence figures are the averages of the ratios for tanks Nos. 1, 

2, 3, 4, 6, and 10, from 1895 to 1900, calculated from dark's analyses 

(1896-1901). For Brockton the figures used cover the period 1897 

to 1904 (Brockton, 1898-1905). A regular seasonal variation is indicated, the organic constitutents reaching their maximum in February 

with the small Lawrence tanks and in March with the large Brockton 

filter. The nitrates show a reciprocal curve, being lowest in February. 

The maximum monthly deviation amounts to about 100 per cent, 

the worst monthly averages being twice as high as the average in 

organic matter. This probably furnishes a fair measure of the 

amount of damage to effluents by winter weather.

The interference with the surface of the beds by winter weather is 

much more serious, and the treatment of crude sewage by intermittent sand filtration at a rate of 0.4 million gallons per acre per day 

can not be recommended. It is believed, however, that experiments 

out of doors and on a larger scale are well worth making in order to 

see if the common rates of 0.06 to 0.1 cannot be somewhat increased. 

No doubt beds operated at higher rates will require more attention 

paid to their surfaces, but it is a question if the raking and scraping 

incident to the filtration of a given volume of sewage will be increased 

by filtering it through a smaller area. It seems probable that the
132 THE PURIFICATION OF BOSTON SEWAGE.

stable material deposited on the surface of a sand filter bears a fixed 

ratio to the amount of sewage filtered; the same thing is very likely 

true of the fatty material which, as Clark has pointed out, penetrates 

below the surface and gradually decreases the efficiency of an old 

sand bed. These inevitable deposits will not be increased by higher 

rates, but will be simply concentrated on a smaller area, while the 

oxidizable organic material can apparently be nitrified under proper 

conditions at considerably higher rates than 0.1. The difficulty of 

scraping during severe winter weather will probably furnish the most 

serious obstacle to increased rates of filtration.

As a rule, sand filters have been constructed without special care 

and operated at haphazard. As this process comes into competition 

with the more elaborate modern methods, it is evidently worth while 

to see what can be done by applying to it the same expert care which 

is understood to be required by a contact or a trickling filter. For 

example, the difficulty of distribution may largely be overcome on a 

practical scale by careful grading and the use of proper distributors, 

if it is clear that this is worth doing. The division of the entire daily 

dose into three or four portions, applied at equal intervals during 

the twenty-four hours, is an expedient which would certainly largely 

increase the capacity of any of the Massachusetts beds now operated 

on the principle of daily or even less frequent dosing. This could be 

accomplished by the use of automatic devices, as at Wauwatosa and 

other plants in the Middle West. It has been tacitly assumed that 

the good results obtained at these filtration areas were wholly due to 

the preliminary treatment of the sewage in the septic tank. It is possible that they may be in part the result of careful operation and the 

application of several doses during the twenty-four hours.

PURIFICATION IN CONTACT BEDS OF COARSE MATERIAL.

The experiments at this station on the contact bed were planned to 

bring out the influence on the results of the treatment of each of the 

following points: Size and kind of filling material; depth of material; 

double and single contact process; treatment of crude and septic 

sewage; and rate of operation. The filters themselves have already 

been described in full detail (pp. 103-105). For convenience of reference, however, the main facts concerning the filter and its operation 

will be restated in each case.

Of the seven primary contact beds all are 4 feet square in area. 

Tanks Nos. 11, 12, 13, 14, and 16 are each 6 feet deep, and Nos. 18 

and 20 are each 4 feet deep.

In all cases the method of operation was as follows: The bed was 

filled during the course of an hour, allowed a two hours' contact, 

emptied in about half or three-quarters of an hour, and allowed to 

stand empty until the next filling. The filling was in all cases con-
PURIFICATION IN CONTACT BEDS. 133

tinuous, and after the first six months two or more fillings of the 

tank per day were evenly distributed over the twenty-four hours.

Tanks Nos. 11, 12, 13, and 14 were run alike throughout the experiments. During July aind August, 1903, they received one filling per 

day. The rate was doubled August 31, 1903, increased to four fillings January 1, 1904, and reduced to three fillings June 24, 1904. 

During the whole period after August, 1903, tank No. 16, the counterpart of No. 13, was run at three fillings. Owing to the superior 

results obtained from tank No. 16 at three fillings over tank No. 13 

at two the rate of the first four filters was increased to four fillings. 

This, after a fair trial, was found to be excessive, and the rate of three 

fillings per day was adopted as the most favorable.

Tank No. 11 was filled with coke about 2 inches in diameter. During the period from June, 1903, to June, 1905, it was run at an average rate of 1.8. No material was removed from the surface during 

the experiment and no serious clogging occurred. The effluent as a 

rule was turbid and putrescible and not satisfactorily purified.

Tank No. 12 was filled with crushed stone 1 inch to 1J-inches in 

diameter. During the two-year period it was run at an average rate 

of 1.4. No material was removed from the surface, although toward 

the end of the period a considerable deposit had accumulated, which 

would have required removal in a short time. The quality of the 

effluent improved steadily during the second year and was at its best 

at the conclusion of the experiment. During the spring of 1905 the 

effluent generally passed the incubator test. The purification 

effected by this filter was largely due to the straining action of the 

sludge layer on its surface.

Tank No. 13 was filled with crushed stone one-fourth to one-half 

inch in diameter. It was run throughout the two-year period at an 

average rate of 1.2. April 6, 1904, ten months after starting this 

filter, it was necessary to remove a 2-inch layer of deposit from the 

surface. This material was earthy in appearance and odor, and was 

easily removed without appreciably disturbing the stones. The 

clogging material extended to a depth of a few inches within the bed, 

but below the surface of the stones was not disturbed. The total 

weight of the substance removed was 26 pounds; its composition on 

analysis was as follows: Moisture, 41 per cent; loss on ignition, 6.9 

per cent; organic nitrogen, 0.1 per cent. March 21, 1905, 2 inches 

of mixed deposit and filter material were removed. The material of 

the filter was clogged badly to a depth of 6 inches, below which the 

.stones were clean. This material was similar to that first removed 

and was not analyzed, except that the stones were 'separated from the 

deposit in a sample of the mixture. The total weight removed was 

141 pounds, of which 56 per cent, or 79 pounds, was deposit. The 

effluent from this filter has been uniformly good and those incubator
134 THE PURIFICATION OF BOSTON SEWAGE.

tests which were made on it showed it to be always nonputrescible. 

Here still more than with tank No. 12 the straining effect of the surface deposit played-an important part.

Filter No. 14 was filled originally with crushed stone one-half to 

1 inch in diameter. During the year of its operation, from July, 

1903, to June, 1904, it received sewage at an average rate of 1.4. No 

material was removed from its surface, although at the end of the 

year there was a considerable accumulation of deposit. The effluent 

was at all times intermediate between those of No. 12 (IJ-inch stone) 

and No. 13 (one-half inch stone). At the end of the first year the 

filter was discontinued to make room for an experiment with a brick 

filter, No. 14A, on the plan of Dibdin's multiple-surface bed, the construction of which has already been described (p. 105). This filter 

was run throughout the second year at an average rate of 2. No 

material has accumulated on the surface, owing to the very open construction. The effluent, of the filter has been uniformly turbid and 

putrefactive.

Filter No. 16 is exactly like No. 13, and was planned originally to 

run parallel with it except as to rate, in order to study the effect of 

two different rates under otherwise like conditions. As already 

stated, it was concluded from the work of this filter that three fillings 

per day were better than two and later that three were better than 

four. This point having been established the filter was used for 

experiments of a special character, the results of which have already 

been published (Phelps and Farrell, 1905). During the second year 

it was run like No. 13 in all respects. Tank No. 16, however, .was not 

cleaned at the beginning of the second year, and therefore effected a 

somewhat higher purification from its greater straining action. Its 

average rate was 1.6.

Tanks Nos. 19 and 20 are each 4 feet deep and filled with crushed 

stone 1 inch to 1J inches in diameter. They were run from June,

1903. to January 1, 1904, with two fillings per day. From January i,

1904.'to the conclusion of the experiments they were given three 

fillings per day. In all respects they were run as nearly alike as possible, No. 19 receiving septic sewage from septic tank No. 10 (thirty 

hours old) and No. 20 receiving crude sewage. The effluents from 

these filters were treated on secondary tanks Nos. 17 and 18, respectively. The purification by No. 19, which took septic sewage, has 

never been satisfactory, the effluent being at all times foul and dark 

colored and generally putrescible. The effluent of No. 20 has been 

much more satisfactory from the start. It is also a striking fact that 

the effluent from No. 20 has been fully as good as that from the finestone filters Nos. 13 and 16, and always superior to that from No. 12, 

from which it differs only in depth and in its consequent lower rate.
PURIFICATION IJST CONTACT BEDS. 135

\

Capacity measurements were made on each bed once a week by 

discharging the effluent into a measuring tank as described above 

(p. 106). The average results by quarters are brought together in 

Table LXV. The results are all expressed in percentages of the total 

cubic capacity of the empty tank. The initial liquid capacity varied 

from 39 to 48 per cent, the highest values of course being found in the 

brick and coke beds. The single-contact beds taking crude sewage 

all decreased in capacity rather steadily, reaching a final value after 

two years of 26 to 33 per cent. The figures do not furnish evidence 

that the falling off had reached its limit, as was shown at Manchester. 

The Dibdin brick filter still showed 40 per cent of open space after 

one year of operation. The capacity of tank No. 19, which received 

septic effluent, was maintained at 38 per cent, and the secondary beds, 

Nos. 17 and 18, retained a capacity of over 35 per cent. -The capacity 

of tank No. 20, which had fallen from 41 to 26 per cent in two years, 

was measured in August, 1905, after three months of rest, and had 

risen to 32 per cent.

TABLE LXV. Capacity of contact filter, by quarters. 

[Percentage of cubic capacity of empty tank.]

No. of filter.

11.................-.-.-.-.-----.-.--.......

13..........................................

14A ........................................

16................---------------.-.........

17..........................................

18..........................................

19........:.-.-.-----.------....---.........

20..........................................

Initial.

46 

40 

44 

48 

42 

39 

42 

41 

41

1903-4.

""37" 

37

& 

36

""46" 

39

44

""37"

37

41 

35 

36

30

34 

36

39 

33 

36

37 

38 

39 

33

1904-5.

38 

33 

35 

48

37 

38 

39 

32

38 

32 

34 

47

37 

37 

38 

31

35 

31

""47 

31

32 

30 

33 

40 

30 

35 

37

26

It is necessary to distinguish clearly between the surface clogging, 

due to the accumulation of material 011 the surface of the bed, and the 

true loss of capacity which affects the lower part of the filter. Since 

in these capacity measurements the tank was always filled just to the 

original surface of the stones, the former phenomenon in no way 

affects the results. The surface clogging depends directly on the size 

of material used, being greatest with the fine beds. In the present 

experiments it was necessary to clean the one-half-inch stone beds once 

a year, while the IJ-inch beds were just clogging so seriously as to 

render cleaning necessary at the end of the second year. The surface 

layer does not extend more than a few inches into the bed, and its 

removal is a simple matter which could be managed as easily as the 

scraping of a sand filter. It must, however, be reckoned with, in the 

cost of operation.

The true loss of capacity, on the other hand, affected tanks Nos. 

11, 12, 13, and 16 about equally, amounting in each case to a reduction 

of about one-fourth, of the original open space. The ratio of the final
136 THE PURIFICATION OF BOSTON SEWAGE.

to the initial capacity was 70 per cent for No. 11, 75 per cent for No. 

12, 75 per cent for No. 13, and 71 per cent for No. 16. Tank No. 20 

showed a greater reduction, to 63 per cent of its original capacity, 

probably because the material carried into the interstices is proportionately greater with a shallow bed. On the other hand, the secondary beds lost only about one-tenth of their open space, the ratio of 

final to initial capacity being 90 per cent for No. 17 and 88 per cent 

each for Nos. 18 and 19. The primary bed taking septic effluent lost 

only 7 per cent of its original capacity in twenty months of operation.

TABLE LXVI. Quarterly averages of analyses of contact-filter effluents. 

TANK NO. 11, PRIMARY-CONTACT BED OF 2-INCH COKE.

Date.

September to November, 1903.. . . 

December, 1903, to February, 1904 

March to May, 1904. ............

September to November, 1904.. . . 

December, 1904, to February, 1905 

March to May, 1905. .............

Temperature 

(°F.).

67

60 

45 

52 

57 

69 

59 

44 

43 

57 

57

Analyses (parts per million).

Turbidity.

150 

150 

160 

120 

90 

140 

130 

130

Nitrogen as 

Albuminoid ammonia.

io

e

4.2 

3.1 

4.4 

3.6 

3.7 

2.7 

3.1 

2.4 

2.8 

2.8 

3.2

Isa'**

M

2.7 

2.3 

3.3 

2.1 

2.5 

1.8 

2.1 

1.7 

2. 1 

1.9 

2.2

m 0

3.0

fl| H ft

1.5 

.8 

1.1 

1.5 

1.2 

.9 

1 

.7 

.7 

.9 

1

i 

g

1.3 ofl

30.8 

23.6 

30.3 

13.8 

23.1 

19.3 

14.5 14 ' 

13.8 

15.4 

18.9

<D

 c

+i

%

0.07 

.44 

.40 

.06 

.24 

.25 

1.60 

.30 

.35 

.61 

.45

1+^>

£

0 

0 

0 

0 

0 

0 

5 

1.3 

1.2 

1.9 

J.I

Oxygen 

consumed.

1

e

23.8 

28.8 

30.7 

20.5 

25.7 

23.7 

20.6 

15.6 

16.7 

19.1 

22.1

o>

3

D"3 

OQ

18.2 

18.2 

20.1 

15.9 

11.4 

13.2 

15.2 

15.5

 d

01!> "o

a

'O

§ 

bC1

0 

0 

0 

0 

0 

0 

.4 

2 

.5 

.7 

.5

TANK NO. 12, PRIMARY-CONTACT BED OF 1 TO 1J INCH STONE.

September to November, 1903.. . . 

December, 1903, to February, 1904 

March to May, 1904. .............

September to November, 1904.. . . 

December, 1904, to February, 1905 

March to Mav, 1905 ..............

60 

46 

52 

57 

69 

59 

45 

44 

56 

57

120 

120 

210 

140 

110 

. 80 

130 

130

4.6 

3.3 

3.6 

3.2 

3.7 

3 

3.3 

3 

2.1 

2.8 

3.2

2.9 

2.4 

2.5 

1.9 

2.5 

1.9 

2.1 

2 

1.6 

1.9 

2.1

1.7 

.9 

1.1 

1.3 

1.2 

1.1 

1.2 

1 

.5 

.9 

1.1

20.4 

25.5 

24.3 

9.9 

20.6 

20.7 

15.9 

15.4 

11 

15.4 

17.6

0.01 

.66 

1.25 

.02 

.41 

.02 

1.43 

.30 

.68 

.61 

.52

0 

0 

0 

0 

0 

0 

2.3 

1.5 

3.7 

1.9 1-3

30.9 

40.6 

32 

22 

32.7 

28.7 

21.4 

18.1 

14.4 

20.1 

25.3

19.2 

19.2 

22.8 

14.9 

15.2 

12 

15.9 

16.3

0 

0

0 

0 

0 

0

0 

.7 

1.8 

.6 

.4

TANK NO. 13, PRIMARY-CONTACT BED OF ONE-FOURTH TO ONE-HALF INCH STONE

September to November, 1903.. . . 

December, 1903, to February, 1904 

March to May, 1904. ......".......

September to November, 1904.. . . 

December, 1904, to February, 1905 

March to May, 1905 .......'... ...

68

60 

45 

52

68

59 

44 

41

56

56

70

70

90

70 

30 

40

60

60

4.5

1.8 

1.7 

1.9

2.5

1.6

1.6 

1.7 

1.2

1.5

2

2.8

1.3 

1.3 

1.3

1.7

1.2

1.2 

1.6 

1.1

1.3

1.5

1.7

.5 

.4 

.6

.8

.4

.4 

.1 

.1

.2

.5

19.1

12.7 

16.8 

7.3

13.6

12.9

11.2 

5.7 

6

8.9

11

1.03

1.33 

.47 

.36

.98

.18

.73 

.51 

.48

.46

.69

0

3.5 

1.3 

5

2.2

1.9

15 

12.3 

8.1

9.5

7.2

20.7

21 

14 

12.3

18.2

16.6

11.9 

7.4 

9.4

11.3

14.3

11.2

11.2

13.7

9.5 

6.4

8.7

9.6

9.8

0

.4 

0 

.1

.3

0

2.1 

3.5

.7

1.5

1.4
PURIFICATION IN CONTACT BEDS. 137

TABLE LXVI. Quarterly averages of analyses of contact-filter effluents Continued. 

TANK NO. 14, PRIMARY-CONTACT BED OF ONE-HALF TO 1 INCH STONE.

Date.

September to November, 1903.. . . 

December, 1903, to February, 1904

Temperature 

(°F.).

60 

45 

51 

57

Analyses (parts per million).

Turbidity.

"ieo"

160

Nitrogen* as 

Albuminoid ammonia.

"3 

 8

4.9 

2.9 

3.4 

3.3 

3.6

In solution.

3 

2.2 

2.3 

2.1 

2.4

In sus- pension.

1.9 

.7 

1.1

L2

Free ammonia.

19.9 

24 

22.5 

11.4 

20

Nitrites.

0.03

.89 

.87 

.13 

.49

Nitrates.

0 

0 

0

.8 

0

Oxygen 

consumed.

"3 

|

32 

31.8 

31 

16.3 

28.3

Soluble.

"14"" 

14

dissolved. Oxygen 

0 

0 

2.5 

.4

TANK NO. 14A, PRIMARY-CONTACT BED OF BRICK.

September to November, 1904.. . . 

December, 1904, to February, 1905

68

59 

45 

43

250

190 

170 

180

200

4.1

4.7 

3.3 

3.5

3.9

2.5

2.5 

2.5 

2.1

2.4

1.6

2.2 

.8 

1.4

1.5

18.1

1(1.2 

14.8 

16 4

\ 

0.09

.27 

.25 

.23

.23

0.1

.6 

.7 

.2

31

25.1

25.8 

27.7

27.5

21.8

18.6 

21 

19.9

20.4

0.1

1,6 

3.7 

.2

1.4

TANK NO. 16, PRIMARY-CONTACT BED OF ONE-FOURTH TO ONE-HALF INCH STONE.

December, 1903, to February, 1904

March to May, 1904. .............

September to November, 1904.. . . 

December. 1904, to February, 1905 

March to May, 1905. .............

61

51

54

 60

69

58 

45

57

58

70

70

90

90 

50 

20

70

70

3.7

1.9

9

1.8

2.2

1.6

1.6 

1.3 

1

1.4

1.7

2.7

1.4

1.2

1.2

1.6

1.3

1.3 

1.1 

.9

1.2

1.3

.8

.6

.6

.3

.3 

.2 

.1

.4

16 4

11.8

23.5

5.9

12.4

6.6

5.6 

3.9 

4.7

5.2

8.1

1 08

.85

1.50

.60

.90

1.34

.63 

.46 

.38

.78

.83

0

0

0

1

.1

5.2

27.4 

11.1

8

13.1 9.8

20

16.8

15

14.3

16.5

13.4

11.7

7.8 

7.5

13.1

12.2

12.2

11.3

10.3

7

9.1

9.6

0

.7

0

.3

.6

1.2

1.7 

2.3 

0

1.6

1.3

TANK NO. 17, SECONDARY-CONTACT BED OF ONE-FOURTH TO ONE-HALF INCH STONE.

June to August, 1903. ............

September to November, 1903.. . . 

December, 1903, to February, 1904 

March to May, 1904. ......'.......

September to November, 1904. . . . 

December, 1904, to February, 1905 

March to May. 1905. ....... '. .....

66

56 

49 

51

55

67

66 

43

55

55

70

70

90

50 

100 

90

80

80

3.1

2.5 

2.3 

3.1

2.7

2

1.3 

2.3 

2

1.9

2.3

2.1

1.9 

1.9 

2.1

1.9

1.5

1.1 

1.9 

1.6

1.5

1.7

1

.6 

.4 

.9

.8

.2 

.4

.5

20.3

21.3 

28.8 

13.6

19.7

14.3

13.5 

12.1 

9.2

12.4

1.37

3.38 

0 

.07

.42

.16

.75 

.28 

.02

.31

.35

0

0 

0 

0

.0

2

8.9 

5 

1.6

6

5.2-

22.3

24.5 

18.5 

16.8

21.6

13.9

11.3 

14.8 

12.8

13.3

16.9

13.8

13.8

11.5

10.4 

12.9 

9.5

11.2

11.7

0

0 

0 

0

0

.3

.9 

1 

1

.8

.6

TANK NO. 18, SECONDARY-CONTACT BED OF ONE-FOURTH TO ONE-HALF INCH STONE.

June to August, 1903. ............ 

September to November, 1903.. . . 

December, 1903, to February, 1904 

March to May, 1904..............

June to August, 1904. ............

September to November, 1904.. . . 

December, 1904, to February, 1905 

March to May, 1905. .............

67 

62 

49

58

61

66

57 

45

54

57

80

80

110

90 

70 

60

80

80

3.5 

2.1 

2.6

2.8

2.5

1.9 

1.2 

1.3

1.7

2.1

2.4 

1.3

1.8 

1.7

1.7

1.6

1.4 

1.1 

.9

1.3

1.1

.8 

.8

.9

.9

.5 

.1 

.4

.4

18.4 

15.2 

17.5

19 Q

15.8

12.9

9 

4.6 

6.5

8.1

11.5

0.30 

.43 

.63 

08

34

.33

2.23 

.13 

1.26

.89

0 

0 

0

.1

1.9

12.1 

15.0 

10

12.1

8.6

20.4

22.8 

14

17 9

19 8

16.6

15.9 

10.6 

10

13.4

14

14

13.3

14.9 

10.1 

9.3

10.7

12.4

0 

0 

0

.8

1.7 

2.3 

2.4

1.7

1.3
138 THE PURIFICATION OF BOSTON SEWAGE.

TABLE LXVI. Quarterly averages of analyses of contact-filter effluents Continued.

TANK NO. 19, PRIMAKY-CONTACT BED OF 1 TO 1J INCH STONE TAKING SEPTIC

EFFLUENT.

Date.

September to November, 1903 . . . 

December, 1903, to February, 1904 

March to May, 1904. .............

September to November, 1904.. . . 

December, 1904, to February, 1905 

March to May, 1905. . ............

Temperature 

(°F.).

57 

47 

52 

56 

67 

57 

43

56 

56

Analyses (parts per million).

Turbidity.

130 

130 

110 

170 

150 

190 

160 

160

Nitrogen as 

Albuminoid ammonia.

"3 

S

EH

3.5 

3.1 

3.3 

2.9 

3.2 

3.1 

3.4 

3.8 

3.5 

3.5 

3.3

3 . "21 

^

2.6 

2.4 

1.6 

2.1 

2.3 

1.8 

1.7 

2.5 

2.8 

2.2 

2.3

» a

3 0 m 'm

a§

M ft

0.9 

.7 

1.7 

.8 

.9 

1.3 

1.7 

1.3 

.7 

1.3 

1

6 

S

oi »'303

aj

!-,

PH

20.8 

24.6 

42.5 

11.2 

22 

25.5 

17.5 

16.9 

19.8 

20.1 

20.9

to

 e

1

0.08 

.38 

0 

0 

.21 

.17 

.62 

.09 

0 

.22 

.21

to

D

1 +^>

fc

0 

0 

0 

0 

0 

.8 

2.3 

1.4 

0 

1.2 

.9

Oxygen 

consumed.

"3 

«

H

32 

31 

36.5 

25.8 

30.4 

29.1 

23.6 

23.4 

30 

26.3 

28

3

3

'o 

M

20.2 

20.2 

21.6 

16.3 

18.5 

17.4 

18.7 

19

T31O

-S

§bfi 

&

O

0 

0 

0 

0 

0 

0 

0 

1.3 

0 

.6 

.4

TANK NO. 20, PRIMARY-CONTACT BED OF 1 TO 1J INCH STONE.

March to May, 1904. .............

September to November, 1904.. . . 

December 1904, to February, 1905 

March to May, 1905..............

67

60

51

68

57 

46

55

57

10fl

130

150

140 

100 

110

120

5.7

3.9

4.7

3.7

4.3

3.8

3.5 

2.4 

2.7

3

3.6

4.4

2.7

3.1

3

2.3

2.3 

1.8 

2

2.1

2.5

1.3

1.2

1.6

1.7

1 ^

1.5

1.2 

.6

.7

.9

20.4

17

OO

16.9

18.4

16.9

16.1 

7.5 

12.6

12.7

0.12

.40

.05

.08

.23

.07

2.05 

.33 

.30

.74

50

0

0

0

0

0

.7

7.6 

9.3 

2.3

6.1

4

29.7

25.2

32

24

26.7

23.4

20.3 

15.3 

15.8

18.6

22.4

17.6

17.6

17.1

15.4 

13.5 

12.8

15

1.5.4

0

0

0

.6

.2

,8 

2.2 

2.9

1.3

.8
TABLE LXVII. General averages of analyses of contact-f

No. of 

tank.

11.....

12.....

13.....

14.....

14A . . . 

16..... 

17o....

IS"....

196....

20.....

Date.

June, 1903, to June, 1905 ....

.....do......................

June, 1903, to June, 1904 .... 

June, 1904, to June, 1905. . . .

June, 1903, to June, 1905. . . . 

.....do......................

.....do......................

.....do......................

.....do......................

Material.

Coke......

.....do....

.....do.... 

Brick.....

Stone..... 

.....do....

.....do....

.....do....

.....do....

Size of 

material 

(inches) .

2V'i

H

E!

I'-IJ 

l -i|

Avernffa

«*gc

rate 

(million 

gallons 

per 

acre 

per 

day).

1.8 

1.4 

1.2 

1.4 

2 

1.2 

1.2 

1.1 

1.2 

1.1

Temperature 

(° F.).

57 

57 

56 

57 

57 

58 

55 

57 

56 

57

Analyses 

Turbidity.

130 

130 

60 

160 

200 

70 

80 

80 

160 

120

Nitrogen 

Albuminoid ammonia.

Total.

3.2 

3.2 

2 

3.6 

3.9 

1.7 

2.3

Ot HO

3.6

In solution.

2.2 

2.1 

1.5 

2.4 

2.4 

1.3 

1.7 

1.5 

2.3 

2.5

In suspension.

1 

1.1 

.5 

1.2 

1.5 

.4 

.6 

.6 

1 

1.1

F

a

mo

Secondary-contact bed. b S
140 THE PUBLICATION OF BOSTON SEWAGE.

The quarterly analyses of the effluents from the several contact beds 

are given in Table LXVI, and the average analyses for each bed for the 

whole period of operation are brought together in Table LXVII. An 

inspection of the latter table and of figs. 18 to 22 will bring out the 

comparative results attained with filling of different material and different size, with different depths of beds, with different rates of operation, with single and double contact beds, and with the treatment of 

crude and septic sewage.

First, as to the kind of filling material, it was desired to see it the 

particularly favorable results reported with the use of coke at London 

would be obtained with Boston sewage. Tank No. 11, filled with 

2-inch coke, is fairly comparable with tank No. 12, filled with IJ-inch 

broken stone. The initial capacity of No. 11 was considerably higher 

than that of No. 12 (46 per cent against 40 per cent), and it decreased 

much more slowly, so that the rate on No. 11 was higher than on No. 

12 with the same number of fillings. As clogging occurred in tank 

No. 12 during the last year of operation, its effluent improved and at 

the end was much better than that of No. 11. A comparison of the 

average analyses for the whole period, however, shows that the effluent 

of No. 11 was slightly better than that of No. 12, in spite of the larger 

size of material and the higher rate. Thus it appears that coke is 

somewhat superior to stone.

On the more important question of the size of material, a comparison of tanks Nos. 12 (IJ-inch stone), 13 (one-half-inch stone), and 14 

(1-inch stone) is instructive. The average analyses given in Table 

LXVII are not comparable, because tanbNo. 14 was operated under 

the conditions mentioned for one year only, and during that year the^ 

applied sewage was strongest. In fig. 18, however, the quarterly 

values may fairly be compared.

As might be expected, both efficiency and clogging increase as the 

size of the material used diminishes. Tank No. 13 gave a better effluent than tank No. 14; No. 14 a better effluent than No. 12. The 

effluents from the 1-inch and IJ-inch stone were never of satisfactory 

quality, except, in the latter case, at the very end of the experiment, 

while that from the one-half-inch stone was almost always clear and 

nonputrescible. The efficiency with half-inch material was reached, 

however, only at the expense of a serious clogging which necessitated 

the removal of 4 inches of sludge from the surface during two years of 

operation, leaving the body of the filter for some distance below the 

surface still badly clogged. These results correspond with those obtained by Dunbar and other German investigators (Dunbar and 

Thumm, 1902). They show that with beds of fine material a good 

effluent may be obtained by a single contact, but at the cost of such 

clogging as to necessitate somewhat frequent removal of the upper
PUKIFICATION IN CONTACT BEDS. 141

portion of the bed. Even t 

after two years, and with such 

of course, produce a stable effluent

le 1^-inch stone showed some clogging 

coarse filling a single contact will not,

QUARTER-YEAR ENDING

300 

ZOO

too

40 

35 

30 

25 

20

> /5

5

J 

J 10

\

' 25

0 2O

\

10 

5 

10 

5 

0 

5 

0

1903 

EPT. DEC. MAR.

/

/

^£"

\

^\

^*

^=^^^~^_

^

\

\

V

xx

\

 - __

'^'

FREE. AM

^ ^._

 : 

x

-^vH\ x

>

ox

\

 \

N \

Xs

UONIA ^

'"^^ tV/

_ 

ALBUMiNi

1 'A" STONE

1904- f$O5 

<UNE SEPT. DEC. MAR. JUNE

^^

 - ""

/

\,s

Y1EN CONSUM

/

\/ /

^

TfATES ~~~

 -

 -

1iD AMMONI*

^^

TURBIDIT

X

X

\

ED

X^ "X,

- -- .-,

/

/

/__,

 ~~

 

"- - 

^^^^

^

"x

"x

^^

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~~ __

 

/e'STONE /"STONE

 ».

\^

^^

"x^

\

^

^ ^

mr^zm

* 14

PIG 18. Comparison of effluents from primary-contact beds of various-sized stone.

Tank No. 14A, construct 

contact (Dibdin, 1904), 

secure permanence by i

rep:?

d on Dibdin's plan of multiple-surface 

esents a logical outcome of-the desire to 

increasing the size of the material. It was filled,
142 THE PURIFICATION OF BOSTON SEWAGE.

as described above, with, bricks laid in regular tiers with, the largest 

obtainable open space, doing away as far as possible with all straining action. Its original capacity of 48 per cent fell in a year only to 

40 per cent, and with three fillings a*day gave a rate of 2 to 50 per cent 

higher than was obtained with any other filters similarly operated, 

with the exception of the coke bed. Its effluent compares favorably 

with that from tanks Nos. 11, 12, and 14, with the exception of its 

higher turbidity. It will be noticed that a general improvement in 

the character of all the effluents took place during the whole period 

and that it was considerably greater than can be accounted for by the 

weaker sewage of the second year. This improvement was manifest 

in all the contact beds to a greater or less degree, and is no doubt in 

part, but only in part, accounted for by the straining action which 

accompanies progressive clogging.

The percentages of albuminoid ammonia and of oxygen consumed 

removed by each filter during each year have been calculated, end the 

increase in the figures in the second year as compared with the first 

is shown in Table LXVIII, expressed as per cent of the first-year 

value. The anomalous results obtained with tanks Nos. 17 and 19 

are due to the very low efficiency of No. 17 during the first year and 

to a deterioration of No. 19, probably due to the overseptic effluent 

with which it was dosed.

TABLE KXVIII. Improvement in percentage efficiency of contact filters in second year of

operation.

[Per cent of first-year value.]

No. of 

tank.

11

12

13

16

17

18

19

20

Albuminoid 

ammonia.

20

25

24

18

20.8

18

19

45

Oxygen 

consumed.

40

83

23

17

71

13

9

32

Data bearing on the effect of contact beds of different depths may 

be obtained by co'mparison of tanks Nos. 12 and 20. Both were 

filled with IJ-inch stone and dosed with three fillings of crude sewage 

per day. The depth was 6 feet for tank No. 12 and 4 feet for No. 20. 

The analyses of the representative effluents are shown in fig. 19. It 

is apparent that the results of treatment in the 4-foot bed are consistently better than in the 6-foot bed. In particular, it will be 

noticed in Table LXVI that the nitrification is more complete in the 

shallow filter, but the difference is scarcely great enough to compensate for the diminished rate.

With regard to the r^te of operation it has been found, as stated 

above, that three daily fillings give the most satisfactory results,
PURIFICATION IN CONTACT BEDS. 143

Between August, 1903, and 

otherwise similar in all respe

January, 1904, tanks Nos. 13 and 16, 

3ts, were operated with two and three

J903

100

25

30

daily fillings, respectively. Tank No. 16, with three fillings, gave the 

best effluent, as indicated in fig. 20. In January, 1904, the rate on 

tank No. 13 was doubled to four fillings. During the next few 

months, while the effluent from tank No. 16 was steadily improving,

QUARTER-YEAR ENDING 1904- 

JUNE SEPT

1905 

MAR. JUNE

\-

\

FREE A,

ALBUMINOiD

6 FT. DEE 

FIG. 19. Comparison of effluents

that from tank No. 13 deteriorated 

insufficient to maintain the 

organisms in the bed, while four 

on their powers. After June 

three fillings and gave appro:?

CONSUMED

FIL TER 12 FILTER 20 

4 FT. DEEP

from primary-contact beds of different depths.

Apparently two fillings are 

maximum efficiency of the purifying 

fillings put a somewhat undue strain 

1904, both beds were operated with 

imately the same results. Those from
144 THE PURIFICATION OP BOSTON SEWAGE.

tank No. 16 were a little better, probably because its surface was not 

cleaned and a considerable straining effect was exerted.

A comparison of the operation of tanks Nos. 19 and 20 furnishes 

interesting results with respect to the value of preliminary septic 

treatment. Both were 4-foot beds of IJ-inch stone, receiving, first, two

zoo 

too

1303 

SEPT. DEC.

QUARTER-YEAR ENDING

IS04- 

JUNE SEPT.

1905 

MAR._____ JUNE

OXYGEN CONSUMED

NITfATES

ALBUMINOID AMMCN/A.

TURBID IT)

 FILTER 13 FILTER. 16

FIG. 20. Comparison of effluents from primary-contact beds at different rates.

fillings, later, three fillings a day. Tank No. 19 received septic effluent 

from tank No. 10, which had been subjected to twenty-four hours of 

septic action and six hours' additional storage in a small dosing tank, 

into which the effluent from No. 10 flowed continuously. The analyses of the effluents from Nos. 19 and 20, as well as from their secondary
PURIFICATION IN CONTACT BEDS. 145

beds, Nos. 17 and 18, are shown in fig. 21. It will be noticed that the 

effluent of tank No. 20 was markedly superior to that of No. 19 in 

every respect, except, for part of the time, in its albuminoid-ammonia 

content. The effluent from No. 20 was often nonputrescible, while 

that from No. 19 was always foul and offensive. As pointed out 

above, the septic treatment was efficient in preventing clogging, the 

final capacities of tanks Nos. 19 and 20 being 38 and 26 per cent, 

respectively. This advantage is, however, dearly bought, since the 

septic effluents from Boston sewage evidently contain substances 

inimical to bacterial action, which seriously interfere with subsequent 

purification. The possibilities of preliminary septic treatment before 

contact filtration can not be considered as exhausted, since only this 

long period (twenty-four hours' storage in the septic tank and six 

hours in the dosing tank) has been tried; a shorter period might 

remove solids without interfering so seriously with the contact bed. 

Furthermore, the harmful effect of the septic treatment might be 

largely minimized by special aeration before final treatment. All 

that the experiments have so far shown is that thirty hours of septic 

treatment yields unsatisfactory results, while crude sewage may be 

treated with the production of a good effluent at the risk of clogging, 

which would necessitate the renewal of the beds at intervals of some 

years. It is probable that a shorter septic period approaching more 

nearly the condition of plain sedimentation would maintain the 

capacity of the beds without corresponding harmful effects. The 

analyses of the effluents from the secondary filters, tanks Nos. 17 and 

18, are also plotted in fig. 21. In nitrogenous constituents and in 

available oxygen the effluent of tank No. 18 was much better than 

that of No. 17. The former was clear and stable, the latter generally 

dark-colored and smelling of hydrogen sulphide and often failing to 

pass the incubator test.

The general results of these experiments on contact treatment, as 

measured by oxygen consumed, are plotted in fig. 22. Like fig. 7 

(p. 68), for experiments at otier places, it shows that a single contact 

will remove from one-third to on&-half of the organic constituents of 

sewage, with the production of an improved but still putrescible 

effluent. Tanks Nos. 13 and 16, of one-half inch stone, form an exception, since their effluents were fairly stable toward the end of 

the experiments. This efficiency, as has been explained (pp. 133-134), 

was obtained at the expense of serious surface clogging. The doublecontact treatment effected a removal of one-third to one-half of the 

remaining organic matter, producing a satisfactory effluent in the case 

of the treatment of crude sewage.

To summarize the conclusions arrived at in regard to the construction of contact beds, it appears that a 4-foot depth gives somewhat

IRK 185 06 10
146 THE PURIFICATION OF BOSTON SEWAGE.

better results than a 6-foot depth,- but with greater capacity loss and 

lower rates. Either coke, brick, or broken stone, or probably any 

other hard material, may be used for filling, with a slight advantage

QUARTER-YEAR ENDING

1904 

JUNE. SEPT.

t9Q5 

MAR. JUNE

100

30

30 -

/

FREE AMMQ

NITRATES

ALBUMINOID AMMONIA

'YGEN CO/VSt

7\

FILTER 17 

FJLTEFt 19

 FILTER 18

 FIL TER ^0

FIG. 21. Comparison of effluents from double-contact systems taking crude and septic sewage.

for coke.. The size of the material is more important than the kind. 

Half-inch stone gives much better results than coarser material, 

yielding a nonputres,cible effluent even with a single contact. The
CONCLUSIONS. 147

surface of such beds must be cleaned once a year or oftener. With 

IJ-inch stone the surface deposits need not be removed so frequently, 

and with still coarser material, such as 2-inch coke, the surface needs 

practically no attention; but all effluents from beds of material over 

one-half inch in diameter require treatment in secondary beds. In 

every case the beds treating crude sewage will lose capacity so rapidly 

as to necessitate renewal.

The contact beds have been operated most satisfactorily with three 

fillings a day, giving a single-contact rate for 6-foot beds of 1.2 with 

fine-stone filling, 1.4 with coarse stone, 1.8 with 2-inch coke, and 

2 with brick. The brick bed might be built, according to Dibdin's 

original plan (Dibdin, 1904), of slate, so as to gain a still larger 

capacity. With any material other tha~i the one-half inch stone a 

second contact would be necessary, reducing the rate on the double 

system, as a whole, to between 0.6 and 1.

\SE

RAW 

EWA6E

FIG. 22. Comparison of sewages a id effluents from single and double contact bedw. 

CONCLUSIONS BEARING ON THE TREATMENT OF BOSTON SEWAGE.

said

this 

have 

and

Nothing has so far been 

trickling over beds of coarse 

recent English experiments 

of all. Three of the tanks 

15 for the whole two years 

were operated at high rates 

per day and produced 

mentation were nonputrefact 

face clogging. It does not se 

the results obtained. The 

tion of the trickling filter are 

weather conditions. While 

be tested in experiments like 

ent that trickling filters of only 

buckets and operated under

W/.

14

] PRIMARY 

I EFFLUENT

17-19 Id-20

SECONDARY 

EFFLUENT

about the process of purification by 

material. According to the results of 

should be the most promising method 

been operated on this principle No. 

Nos. 22 and 23 during 1904-5. They 

from 1.5 to 2.5 million gallons per acre 

somewhat turbid effluents which after sedii ve. They were entirely free from surem justifiable however to lay stress on 

two most important points in the operalie distribution system and the effect of 

sand filters and contact beds may fairly 

jhose recorded in this paper, it is appar16 square feet area, dosed with tipping 

cover, do not furnish a criterion of actual
148 THE PURIFICATION OP BOSTON SEWAGE.

conditions. It has therefore been decided to conduct during 1906 a 

series of experiments on a larger scale, out of doors, and to postpone 

any discussion of trickling-filter results until those experiments are 

completed. The conclusions in this paper will, therefore, be limited 

to the discussion of the septic, sand, and contact processes.

It will be necessary in any treatment to screen out large floating 

bodies and to settle out mineral detritus. This process should be 

limited to a sedimentation of a few minutes. Under such conditions 

the settled material amounts to about 1,600 pounds per million gallons of sewage and is of such a character that it may be spread out on 

land without fear of nuisance.

A further removal of the suspended organic matter may be effected 

if desired by treatment in the septic tank. An open tank operates as 

well as a closed tank, and there is no marked advantage in filling the 

tank with stone. Varying the storage period from twelve to fortyeight hours produces no difference in the effluents which is measurable 

by analytical results. All the tanks removed nearly two-thirds of the 

suspended matter and yielded an effluent which was clear but much 

darkened by hydrogen sulphide. The tanks on an average received 

50 pounds of nitrogen as albuminoid ammonia (dissolved and suspended), of whichrSO pounds were discharged in the effluent, 15 to 17 

pounds decomposed and 3 to 5 pounds stored as sludge. In the 

decomposition of sludge the length of the septic period is of great 

importance. The amount of organic solids stored, undecomposed, 

per million gallons of sewage passed, is twice as great with a fortyeight-hour period as with a twenty-four-hour period and four times as 

great as with a twelve-hour period.

Under the conditions of these experiments crude Boston sewage has 

been successfully filtered through a 2-foot bed of sand with an effective 

size of 0.14 millimeter, at a rate of 0.4 million gallons per acre per day, 

divided into four doses in the 24 hours. Such high rates should not be 

expected in actual practice, but it is believed that with care in construction and operation the sand filter may be efficient at higher rates 

than have been generally advocated. The effluents obtained from 

the sand beds were clear, bright, and well purified. The depth of the 

beds can not safely be reduced below 2 feet. Preliminary septic treatment for twelve or twenty-four hours does not improve the effluents 

obtained with sand filtration, although it makes the care of the surface of the beds somewhat easier.

Crude Boston sewage may be treated in single-contact beds of 

fine stone (one-half inch in diameter) at a rate of about 1.2 million 

gallons per acre per day. The effluent is only partially purified, but 

is generally so stable as to be discharged into a considerable volume 

of water without any tendency to create a nuisance. The beds clog 

rapidly and the surface needs much attention. The double-contact
ACKNOWLEDGMENTS BIBLIOGBAPHY. 149

system of treatment, in primary beds of 2-inch material and secondary beds of one-half-inch material, yields a fairly well purified 

and stable effluent at a rate on the combined double system of about 

0.7 million gallons per acre per day with beds 6 feet deep. Such a 

system clogs much less seriously, but nevertheless loses sufficient 

capacity to require renewal every few years. Preliminary septic 

treatment obviates this capacity loss to a considerable extent. In 

these experiments a thirty-hour septic period produced an effluent 

which without aeration was so difficult to purify as to interfere seriously with the efficiency of the contact beds. There is little doubt 

that this difficulty could be overcome by aeration or by shortening 

the septic period. The most practical of the methods which have 

been studied would appear to be the treatment of sewage, either 

sedimented or subjected to a very short period of septic action, in 

double-contact beds. The process of trickling filtration remains to 

be considered in a further report, but incomplete results obtained 

at the present time indicate that this method will probably prove 

superior to any so far tested.

ACKNOWLEDGMENTS.

The writers desire to express their acknowledgments to Mr. E. S. 

Dorr, of the Boston sewer department, for many courtesies; to 

Messrs. W. S. Johnson and Leonard Metcalf for advice in regard to 

certain points in the conduct of the experiments; to Prof. L. P. 

Kinnicutt and Mr. G. W. Fuller for suggestions concerning the presentation of results; and to Messrs. G. R. Spaldmg, W. H. Beers, 

and W. T. Carpenter for assistance in analytical work and in the 

preparation of tables and diagrams.

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152 THE PUEIFICATION OF BOSTON SEWAGE.

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154 THE PURIFICATION OF BOSTON SEWAGE.

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INDEX.

A.

Accrington, England, septic treatment at... 49,

50,51,118 

trickling filtration at............. 80,83,84,88

Acheres, France, sewage farm at. See Paris. 

Acid-iron waste, effect of, on sewage..... 12,41,50

Acton, England, septic treatment at....... 51

Adeney process of sewage treatment, use of,

in Ireland....................... 35

Aeration, forced, experiments on........... 75-76

Aerobic oxidation. See Contact beds; Filtration; Sewage fanning. 

Albumen, oxidation of..................... 16

Albuminoid ammonia, method of expressing values for................... 17

Aldershot, England, sewage farm at....... 27

Algae, influence of, in oxidation............. 17

Alliance, Ohio, chemical precipitation at... 96 

Altrincham, England, sewage farm at...... 27

Alvord, J. W., on septic process............ 46,48

Ammonia, method of expressing values for. 17 

Anaerobic putrefaction. See Septic tank 

Analyses,- description of, at sewage expe: 

ment station................. 107-111 

i,80,117 

3,61,66, 

146,147 

. 27,90 

. 117 

, 58,129 

90,117 

of septic effluents.......... 40,45,47,4 3,57,58,

of chemical effluents....... 31,33,41,5

of contact effluents........... 56,57,5

 68,70,71,86,88,136-139,143,144 

of effluents from sewage farms.. 

of effluents from strainers......

of sand-filter effluents........ 39,40,4

of sedimentation-tank effluents....

68,70,71,77,82,83,88,90,117 

of septic-tank contents..............

of sewage.*......'.............. 27,31,

41,45, 47,48,57,58,61,68, 

80,81,82,83,88,90,114,117 

of trickling-filter effluents.........

122-123 

. 124 

3,39,40, 

3,71,77, 

123,147 

. 77,

78,80,81,82,83,84, & i-86,88 

of water from Illinois and Michigan Canal.

Analytical methods. See Methods, analytical.

Andover, Mass., intermittent filtration at 

septic treatment at.............

Ashtead, England, experiment with sewajje 

tank at.................

trickling filtration at............

Aylesbury, England, contact treatment 

at.......................

treatment in coarse filters at.....

B.

Bacteria, disposal of, in sewage puriflcatio: 

presence of, in sewage.................

r61e of, in sewage purification.........

17,35,37,38,44,

58, <

17

40

52

43,45

78

),70 

118

. 12,37 

. 11,37 

. 13, 

)4,72,73

Page.

Bailey-Denton, J., experiments by, on sewage filtration.................... 36

Baker, M. N., on anaerobic filters........... 45

on chemical precipitation............... 31

on contact process..................... 61,89

on English purification processes....... 91

on septic process..................... 46,50,51

on sewage farming...................... 28

on trickling filtration................... 80,88

See also Rafter, G. W., and Baker, M. N.

Barbour, F. A., on septic process..... 50,51,53,121 

on septic treatment of sludge........... 48

Barking, England, chemical precipitation

at.............................. 30-31

contact treatment at. 54,55,56,57,63,66,67,73 

dissolved oxygen in Thames River at... 19

Barrhead, England, contact treatment at.. 73 

septic treatment at..................... 51

Barwise, S., on contact process............. 59,67

on septic process........................ 49

on sewage farming...................... 26

on sewage nitrification.................. 38

on trickling filtration....... 79,80,82,83,84,86

Battersea, England, dissolved oxygen in

Thames River at................ 19

Beaumont-Leys sewage farm. See Leicester, England.

Beddington, England, sewage farm at...... 27

Beers, W. H., acknowledgments to......... 149

work of.................................. 9

Belfast, Ireland, trickling filtration at...... 87

Bell, , on trickling filtration........... 80-81

Berlin, contact treatment at............. 59,65,74

first sewerage in........................ 11

royal testing station at, investigations

of, on purification processes.... 93-94

sewage farms at........................ 25

trickling filtration at................... 94

See also Grosslichterfelde.

Birmingham, England, chemical precipitation at.......................... 31,90

contact treatment at............. 58,66,67,74

septic treatment at..... 46,48,49,50,52,90,118

sewage farming at...................... 26,&0

trickling filtration at............. 79-80,83,91

Blackburn, England, contact treatment

at......................... 67,68,69,70

treatment in coarse filters at........... 118

Blackstone River, pollution of, by sewage

of Worcester, Mass............. 32-33

Blackwall, England, dissolved oxygen in

Thames River at............... 19

Bokorny, , on oxidation.............. 17

Boullanger, E., and Massol, L., on work of

bacteria in sewage purification . 38

Bredtschneider, A., on contact process..... 72

155
156 INDEX.

Bredtschneider, A., and Thumm, K., investigations by, on purification 

processes....................... 94

on contact process...................... 58,71

on sewage fanning...................... 26

on trickling filtration............. 78,80,81,83

Bridgeport, 111., analysis of water of Illinois

and Michigan Canal at......... 17

Brockton, Mass., intermittent filtration

at........................... 40,41,131

septic treatment at..................... 48

sewage of, strength of.................. Ill

sludge from filtration process at....... 42

Bruch, W., on purification processes.. 65,66,74,93 

Brunswick, Germany, sewage farming at... 26 

Bunker, G. C., work of..................... 9

Bunzlau, Prussia, sewage farming at....... 24

' Burnley, England, contact treatment at. 63,67,73 

septic treatment at................. 49,51,118

Burton, England, trickling filtration at.... 84

Buxton, England, trickling filtration at.... 82,84

C.

Calmette, A., on purification processes..... 94

Cambridge, England, sewage farm at....... 27

Cameron, Donald, development of anaerobic

process by...................... 43-44

Campbell, J. L., experiments by, on purification processes.................. 91

Candy, , on trickling filtration....... 82

Candy-Whittaker trickling filter, construction of.......................... 80

Canton, Ohio, chemical precipitation at.... 96

Carlisle, England, contact treatment at.... 67

Carpenter, W. T., acknowledgments to..... 149

work of................................. 9

Caterham, England, septic treatment at... 52 

trickling filtration at................... 78

Cellulose, oxidation of...................... 16

Chadwick, , and Murchison, , 

theory of, concerning origin of 

infectious disease............... 10

Champaign, 111., sewage tank at............ 43

Chapel-Izod, Ireland, chemical precipitation at.......................... 35

Charlottenburg, Germany, contact treatment at......................... 58,94

Cheltenham, England, sewage farming at.. 26 

Chemical precipitation, cost of............. 31,34

defects of............................... 32

disposal of sludge from................. 32

effluents of, analyses of. See Analyses. 

English patents for..................... 29,31

. ratesof.............................. 30,32,34

treatment of sewage by................ 29-35,

41,89,90,91,92,93,94,96,117,118 

Chesbrough, E. S., sewerage system designed by, for Chicago.......... 10-11

Cheshire, England, sewage farm at......... 27

Chesterfield, England, trickling nitration at. 80,84 

Cheyenne, Wyo., sewage farm at........... 28,96

Chicago, first sewerage in................... 10-11

Chondrin, oxidation of..................... 16

Chorley, England, chemical precipitation at. 118

Page. 

Clark, H. W., on contact process........... 72,73

on intermittent filtration............. 131,132

on septic process.......^............. 44,50,52

on trickling filtration................... 85

on variations in strength of sewage..... 107

Clark, H. W., and Gage, S. D., on bacteria

in septic treatment............. 48

Climate, effect of, on purification processes 22, 

28-29,41-42,86,96,130-132

Clinton, Mass., intermittent filtration at... ^,42 

Cloaca Maxima, function of................ 9

Clowes, F., and Houston, A. C., experiments

by, on contact process.......... 56

on contact process.... 55,56,57,59,63,65,66,67

on purification processes at London.... 89

Columbus, Ohio, experiments at, on purification processes................ 95-96

trickling filtration at................... 86

Concord, Mass., intermittent filtration at.. 40,42 

Connecticut, intermittent filtration in...... 95

Connecticut sewage commission, on dissolved gases in Thames River, 

England........................ 19

Contact bed, multiple-surface. See Multiple-surface bed.

Contact beds, capacity of. 59,65,92,135-136,140,142 

effluents from, analyses of. See Analyses, 

rates of treatment in.... 55,56,57,58,67,68-69,

70,71,73,133,134,139,142,147,148,149 

treatment of sewage in............. 53-75,88,

89,91,92,93,94,95,96,132-147,148-149 

Copeland, W. E., experiments by, on purification processes................ 95-96

Corbett, , experiments by, on trickling

niters........................... 77,78

on trickling filtration................... 82

Craigentinny, Scotland, sewage farm at.

See Edinburgh. 

Creer, A., investigations by, on purification

processes........................ 91

Crops, growing of, on filter beds............ 41

healthfulness of, grown on sewage farms. 28 

See also Sewage farming. 

Crossness, England, chemical precipitation

at............................... 30-31

contact treatment at................ 56,57,66

dissolved oxygen in Thames River at... 19 

septic treatment at..................... 49

Croydon, England, contact treatment at... 67 

sewage farm at......................... 27

D.

Danzig, Prussia, sewage farm at........ 24-25,26

Deer Island Light, Boston Harbor, sewage

discharged near, amount of..... 20

Degener process of sewage treatment, use

of, in Germany................. 34-35

Derbyshire, England, trickling filtf ation in. 80 

Detritus, removal of......................' 114-116

See also Screening: Sedimentation. 

Dibdin, W. J., experiments by, on contact

process..............J........ 54-56,66

investigations by, on chemical precipitation..........r ..i.:............. 29-30
INDEX. 157

Page.

Dibdin, W. J., on anaerobic putrefaction... 52 

on chemical precipitation............... 31

on contact process................... 57,59,72

on multiple-surface bed............ 59,141,147

 on necessity of anaerobic putrefaction.. 53 

on oxidation............................ 16,76

on role of bacteria in sewage purifies tion. 54 

on self-purification of Thames River,

England.... v .................. 18

on sceptic process........................ 50,74

on trickling filtration................ 77,81.90

Dilution, disposal of sewage by............ 16-23,

26,90,92,93,94,96 

Disinfection processes of sewage treatment,

defects of....................... 35

Dorr, E. S., acknowledgments to........... 149

Double-contact process. See Contact beds. 

Drift, Glacial, use of, in construction of

filters........................... 41

Dronfield, England, trickling filtration at.. 84 

Drown, T. M., work of, on sewage-purification investigations.............. 37

Ducat, , experiments by, on trickling

filters........................... 77,80

on trickling filtration................ 81,82,83

Ducat trickling filter, construction of...... 79

Du Mar&s, .T. B., on sewage farming........ 24

Dunbar, , experiments by, on contact

process.......................... 93

on contact process...................... 72

Dunbar, , and Thumm, K., on contact

process.........^................' 61,

62,65,66,68,72,73,74, 75,93,140 

on work of niters....................... 108

Dundrum, Ireland, chemical precipitation

at............................... 35

Dupre', , on rdle of bacteria in sewage

purification..................... 54

E.

East Cleveland, Ohio, septic treatment at.. 46,76 

Eastry. England, contact treatment at.... 71

Eddy, H. P. See Kinnicutt, L. P., and

Eddy, H. P.

Edinburgh, Scotland, sewage farming at... 24,26 

Effluents, analyses of. See Analyses.

septic composi tion of, figure showing... 120 

England, chemical precipitation in........ 29-32,

89,90,91,92,93 

contact treatment in.... 54-57,58,59,61-64,65,

66,67-68,69,70,71,73-74,88,89,91,92 

intermittent filtration in............... 36

septic treatment in............... 43-44,45, 46,

47, 48, 49,50,51,52,53,88,89,90,91,92 

sewage in, amount of................... 11

composition of...................... 15-16

sewage-disposal practice in, recent tendencies in........................ 88-93

sewage farming in . 24,25,26-27,28,90,91,92,93

trickling filtration in.. 75,77-84,87,89-9C,91,92

See also Great Britain; London; namei

of towns. i

Page. 

Erith, England, dissolved gases in Thames

River at..................... A. 19

Exeter, England, contact treatment at..... 63,

65-66,67 

septic treatment at......... 43,48,49,50,88-89

F.

Falkenberg, Germany, sewage farm at. See

Berlin.

Fanning, sewage. See Sewage farming. 

Farrell, F. W., work of..................... 9

See also Phelps, E. B., and Farrell, F.W. 

Fat, oxidation of........................... 16

Filter, contact. See Contact beds.

intermittent. See Filtration, intermittent.

intermittent continuous. See Filtration, trickling.

ladder. See " Ladder filters." 

percolating. See Filtration, trickling, 

sand. See Filtration, intermittent, 

sprinkling. See Filtration, trickling, 

trickling. See Filtration, trickling. 

Filtration, rates of, in anaerobic filters..... 45

rates of, in contact beds. 55,56,58,67,70,71,73,

87, 133, 134, 139, 140,142, 143, 148, 149

in sewage farming............... 25,26,27

Filtration, intermittent, cost of, at Massachusetts plants................. 42

effect on, of winter weather .... 41-42,130-132

/' effluents from, analyses of. See Analyimpracticability of, in England......... 88

limitations of........................... 53-54

rates of.......................... 36,37,38,39,

40, 42, 52, 54,127,128,130,131,132* 148 

treatment of sewage by............. 7,

« 12,35-42,52,94-95,96,126-132,148 

Filtration, trickling, effluents from, analyses of. See Analyses.

rates of.. 75,77,78,82-83,84,87,88,90,92,96,147 

treatment of sewage by................. 8,

75-88,89-90,91,92,94,95,96,147-148 

See also Contact beds. 

Fond du Lac, Wis., septic treatment at.... 95

Fowler, , on gas production in septic

tank............................ 44

Framingbam, Mass., intermittent filtration

at............................ 39,40,94

sewage of, strength of.................. Ill

France, experiments in, on purification

processes....................... 94

Frankfurt am Main, Germany, sedimentation at.......................... 116

Frankland, Edward, experiments by, on

sewage filtration................ 35-36

Frankland, Percy, experiments by, on purification processes............... 89

Free ammonia, method of expressing value

for.............................. 17

Frost, W. D., on typhoid bacilli in water.... 11

Fuchsine, use of, in analyses............... 110
158 INDEX.

Fuller, G. W., acknowledgments to........ 149

on chemical precipitation............... 34

on contact process...................... 58,70

on organic nitrogen in sewage.......... 108

on sewage in Massachusetts cities...... 11

on sewerage systems and purification

plants in United States......... 23,96

Fuller, , experiments in charge of, at

Columbus, Ohio................ 95-96

G. 

Gage, S. D. See Clark, H. W., and Gage,

S. D.

Gardner, Mass., intermittent filtration at.. 39,

40,42,94 

sewage of, strength of.................. Ill

Garfield, , on trickling filtration...... 82

Gelatin, oxidation of....................... 16

Gennevilliers, France, sewage farm at. See

Paris.

Germany, chemical precipitation in... 32,34,93,94 

contact treatment in................... 58,

59,60-61,65,66,68,72,73,74,75,93,94 

early sewerage systems in.............. 11

septic treatment in..................... 93,94

sewage-disposal practice in, recent tendencies in........................ 93,94

sewage farming in.......... 24,25,26,28,93,94

trickling filtration in................... 94

Glasgow, Scotland, chemical precipitation

at............................... 32

septic treatment at..................... 50

Gooch crucible, use of, in analyses.......... 110

Goodnough, X. H., on capacity of sewagedisposal plants................. 42

on self-purification of streams ......... 21-22

Gravesend, England, dissolved oxygen in

Thames River at............... 19

Great Britain, health of towns commission,

investigations of......... n...... 10

local government board, influence of, on

sewage-disposal projects..... 91-92,93

metropolitan sewage commission, investigations of................. 10

on sewage disposal................. 92

on sewage farming.................. 24

rivers pollution commission, investigations of......................... 10

on chemical precipitation........... 29

on self-purification of streams...... 17

on sewage disposal.............. 35-36,92

royal commissions of, investigating

sewage disposal, etc.,-list of.... 10

royal sewage commission, investigations of...................... 10,92-93

on chemical precipitation........... 91

on contact process.................. 57,

59,63,64,66,70,74,91 

on effect of sewage on shellfish..... 21,92

on London sewage.................. 11

on necessity of anaerobic putrefaction ............................. 52-53

on sedimentation................... 91

on septic process................... 49-50

on sewage farming............... 29-27,28

on sewage nitrification............. 38

on trickling filtration. 76,77,80,81,83,85,87

Paga 

Great Britain, sewage of towns commission,

investigations of ............... 10

sewage of towns commission, on sewage

disposal........................ 92

on sewage farming.................. '/4

Greeley, Colo., sewage farm at............. 96

Greenhithe, England, dissolved oxygen in

Thames River at............... 19

Greenwich, England, dissolved gases in

Thames River at............... 19

Griggs, J., on purification processes at Columbus, Ohio................... 96

Grossbeeren, Germany, sewage farm at.

See Berlin. 

Grosslichterfelde, Germany, experiments at,

on purification processes....... 93

Griinbaum, A. S., on sewage disposal in

Germany....................... 34-35

H.

Hamburg, Germany, contact treatment at.. 58,

59,60-61,65,66,68,72,73,74,75,93

first sewerage in........................ 11

Hygienic Institute of, experiments at,

on purification processes....... 93,94

Hammersmith, England, dissolved gases in

Thames River at............... 19

Hampton, England, contact treatment at.. 64 

septic treatment at..................... 50

Hanley, England, trickling filtration at..... 82

Hansen, P. See Woodman, A. G., Winslow,

C.-E. A., and Hansen, P. 

Harding, T. W., investigations by, on purification processes............... 89

Harding, , on trickling filtration.. ... 82,87

Harrison, W. H., investigations by, on purification processes............... 89

on septic process........................ 45

Hastings, Nebr., sewage farm at............ 96

Hazen, Alien, construction of trickling filter

by.............................. 75

experiments by, on chemical precipitation............................. 29

experiments on sewage purification in

charge of....................... 37,38

on septic tanks......................... 120

Health, board of, Massachusetts, investigations by, on sewage purification. 6,7, 

23,29,36-37,38-40,107,117 

on disposal of sewage in the sea......... 20-21

on intermittent filtration............... 39

on seasonal conditions of Merrimac 

River at Lawrence, Mass., 1899- 

1900............................. 23

See also Lawrence, Mass., experiment

station at. 

Health of towns commission, Great Britain.

See Great Britain.

Hendon, England, trickling filtration at. 77,79,83 

Hering, R., on self-purification of streams... 21,22 

Hering, , experiments in charge of, at

Columbus, Ohio................ 95-96

Hermite process of sewage treatment,

description of................... 35

Hewson, T., investigations by, on purification processes................... 89
INDEX. 159

Hopedale, Mass., intermittent nitration at. 40 

Hoppe-Seyler, , on character of septic

effluent......................... 121

Horfield, England, trickling filtration at.... 77,79

Houston, A. C. See Clowes, F., and Houston, A. C.

Huddersfield, England, purification processes at...................... 49-50,91

Hyde, England, trickling filtration at....... 83,84

I.

Iddesleigh, Earl of, investigations in charge

of............................... 92-93

Illinois, septic treatment in................. 95

Illinois and Michigan Canal, self-purification

in. ........................>..... 17

Incubator test, description of.............. 109-110

Institute of Technology, Massachusetts. 

See Technology, Massachusetts 

Institute of.

Intermittent filtration. See Filtration, intermittent. 

Ireland, chemical precipitation in........... 35

Irrigation, broad. See Sewage farming. 

Irwell district, England. See Mersey and 

Irwell district.

J.

Jackson permanent standards, use of, in

analyses........................ 110

Jackson turbiditneter, use of, in analyses.... 110

Johnson, G. A., experiments toy, on purification processes................... 95-96

on self-purification of streams.......... 22

Johnson, W. S., acknowledgments to....... 149

Jordan, E. O., Russell, H. L., and Zeit, F. R.,

on typhoid bacilli in water...... 11

K. .

Kew, England, dissolved oxygen in Thames

Riverat........................ . 19

Kewanee, 111., septic treatment at.......... 95

Kimberley, A. E., experiments by, on purification processes................ 95-96

Kingston, England, chemical precipitation

at............................... 118

dissolved gases in Thames River at..... 19

Kinnicutt, L. P., acknowledgments to...... 149

on German sewage-disposal practice.... 93

on septic process........................ 50

on trickling filters....................... 79

Kinnicutt, L. P., and Eddy, H. P., on septic

process......................... 44

Knostrop sewage works (Leeds, England),

contact treatment at........... 63

L.

"Ladder filters," experiments with, at

Leeds, England................. 45

Lake Forest, 111., septic treatment at.. 46,51,53,95 

Langwith, England, trickling filtration at.. 84 

Latham, Baldwin", experiments by, on puriLawrence, Mass., chemical precipitation at. 117 

contact treatment at..... 53,57-58,68,69,70,75 

experiment station at, establishment of. 23,37

°age.

Lawrence, Mass., experiment station at, investigations at, on sewage purification.............. 6,7,23,37,38-39,

44,45, 46,47, 48,49,50, 51,53,57-58,

68,69,70,75,107,117,121,126-127,131

intermittent filtration at. 37, 38-39,126-127,131

sedimentation at....................... 117

septic treatment at..................... 44,

45,46,47,48,49,50,51,107,117,121 

sewage of, strength of................... Ill

straining at............................. 117

See also Merrimac River.

Leamington, England, sewage farming at.. 25

Leeds, England, chemical precipitation at.. 89

contact treatment at................... 62,

63,66,67,68,69,70,71,74,89,118 

experiments with " ladder filters" at... 45 

septic treatment at.. 45,46,47,48,49,50,53,118 

trickling filtration at................... 79,

80,81,83,84,85,86,87,88,89-90 

Leicester, England, contact treatment at... 63,

68,69,70,73 

septic treatment at..................... 49

sewage farm at......................... 27,91

Leicester, Mass., intermittent filtration at.. 40,42 

Letts, , experiments by, on trickling

filtration....................... 87

Liernur sewerage system, use of, in Holland

and Belgium.................... 34

Lille, France, experiments at, on purification processes.................. 94

Local government board, Great Britain.

See Great Britain. 

Lockport, 111., analysis of water in Illinois

and Michigan Canal at.......... 17

London, chemical precipitation at. 29-31,89,92,118 

contact treatment at.... 54-56,57,67,73,74,88

regulations in, concerning discharge of

waste........................... 9,10

sedimentation at....................... 116

septic treatment at..................... 49,50

'sewage of, amount of................... 11

See also Barking; Battersea; Blackwall; Crossness; Greenwich; 

Hammersmith; Woolwich. 

London Bridge, England, dissolved oxygen

in Thames River at............. 19

Long, , investigations by, of self-purification in Illinois and Michigan 

Canal........................... 17

Long Eaton, England, trickling filtration at 84 

Los Angeles, Gal., sewage farm at.......... 28,96

Lowcoek, S. R., construction of trickling

filter by......................... 75

Lynn, Mass., effect of sewage disposal in

shallow water at............... 21

M.

McManus, J.H.,and Walker, A. W., investigations by, on effects of sewage disposal in Boston Harbor.. 20

Madison, Wis., septic treatment at......... 95

trickling filtration at................... 95

Maidstone, England, contact treatment at. 64

Malchow, Germany, sewage farm at. See 

Berlin,
160 INDEX.

Page.

Malvern, England, trickling filtration at... 75 

Manchester, England, chemical precipitation at.......................... 31,89

contact treatment at................... 58,

61,63,66,67-68,69,70,71,73,74,89 

loss in capacity of contact beds at, diagram showing.................. 64

screening at............................ 114

sedimentation at..................... 114,116

septic treatment at................. 50,53,118

trickling filtration at................... 87

Manchester, England, rivers department, on

capacity of contact beds........ 60

Mansfield, Ohio, septic treatment at....... 95

Mansfield, , septic treatment at...... 51

Marion, , septic treatment at......... 51

Marlboro, Mass., intermittent filtration at. 39,

40,42,94 

Martin, A. J., on anaerobic putrefaction.... 51,52

on British commissions................ 10

on contact process................ 59,60,65,67

on removal of suspended solids......... 118

on septic process....................... 49

on trickling filtration................... 83,87

Massachusetts, intermittent filtration in... 94-95 

metropolitan sewerage district of, map

showing........................ 97

purification plants in................... 23,94

Massachusetts board of health. See Health,

board of, Massachusetts. 

Massachusetts Institute of Technology. 

See Technology, Massachusetts 

Institute of.

Massol, L. See Boullanger, E., and Massol, L.

Mawbey, E. G., investigations by, on purification processes............... 91

Meriden, Conn., intermittent filtration at.. 39 

Merrimac River, experiment station on, at 

Lawrence, Mass. See Lawrence, 

Mass, 

seasonal conditions of, at Lawrence,

Mass., 1899-1900................. 22,23

Mersey and Irwell district, England, contact

treatment in.................... 74

Merthyr Tydvil, Wales, experiments on sewage filtration at................ 36

Metcalf, Leonard, acknowledgments to.... 99,149

on receptacles for excreta in Paris...... 43

Methods, analytical, discussion of....... 107-111

Metropolitan sewage commission, Great

Britain. See Great Britain. 

Milan, Italy, sewage farming at............ 24

Millbury, Mass., nuisance created at, by

Worcester sewage.............. 32,33

Mills, H. F., investigations on sewage purification in charge of............ 37,53

on composition of sewage.............. 13

on intermittent filtration............... 37

Moon Island, Boston Harbor, detritus at... 116 

sewage discharged at, amount of....... 20

Mouras, , invention of sewage tank by. 43 

Mucking, The, England, dissolved oxygen in

Thames River at................ 19

Mueller, Alexander, on sewage purification

by micro-organisms,............ 35

Page. 

Multiple-surface bed, treatment of sewage

in ...... 59,134,135,137,139,141-142,147

Muntz, A. See Schloesing, T., and Muntz, A. 

Murchison, . See Chadwick^ ,

and Murchison, .

N. 

Naburn disposal works (York, England),

contact treatment at............ 63

trickling filtration at.................... 88

Natick, Mass., intermittent filtration at.... 40,42

New York, disposal of sewage in tide water

at............................... 20

Newbury, England, contact treatment at... 64 

Newlands, J. A., work of.................... 9 ,

Newport, R. I., experiments at, on forced

aeration......................... 75-76

Nichols, W. R., reports by, on sewage disposal. ........................... 23

Nitrification. See Bacteria.

Nore, The, England, dissolved oxygen in

Thames River at......-.-....... 19

Nottingham, England, sewage farm at...... 27

Nut Island, Boston Harbor, sewage discharged near, amount of........ 20

O. 

Ohio, chemical precipitation in.............. 96

purification plants in.................... 95

septic treatment in...................... 51

Oldham, England, contact treatment at. 63,73,91 

sedimentation at........................ 91

septic treatment at................. 51,52,118

Osdorf, Germany, sewage farm at. See

Berlin.

Oxygen, amount required for complete oxidation .......................... 16

P.

Paris, regulation in, concerning discharge

of waste......................... 9

sewage farms at......................... 25

Parry, Kaye, chemical method used by, in

Ireland...........-.-.-.-.-..-.. 35

Pawtucket, R. I., sludge from filtration process at........................... 42

Perkins, W. H., experiments by, on purification processes................... 89

Phelps, E. B., work of....................... 7

See also Winslow, C.-E. A., and Phelps, 

E. B.

Phelps, E. B., and Farrell, F. W., on contact

process......................... 72,73

Philbrick, E. S., on sewage tank............. 43

Pittsfield, Mass., intermittent filtration at.. 40,42

Plainfield, -, septic treatment at....... 51

Pratt, R. W., jr., on forced aeration......... 76

on Ohio purification plants.............. 51,95

Precipitation. See Chemical precipitation.

Prescott, S. C., work of...................... 9

Providence, R. I., chemical precipitation at. 34,96

R.

Rafter, G. W., and Baker, M. N., on analyses of water from Illinois and 

Michigan Canal................. 17

on manurial value of sewage'............ 28
INDEX. 161

Reid, G., experiments by, on trickling filtration............................. 82

See also "Wilcox, J. E., and Reid, G. 

Ribble district, England, contact treatment

in............................... 74

Richmond, England, chemical precipitation

at............................... 118

Rideal, S., on bacterial action............... 73

on con tact process.......-_. ....... _..... 56

on Hermite process of sewage treatment 35 

on necessity of anaerobic putrefaction.. 52 

on self-purification of streams........... 20

on septic process..................... 43-44,52

on sewage farming...................... 25

on sewage nitrification.................. 38

on trickling filtration................... 78,83

Rivers, self-purification of............ 17-20,21-23

Rivers pollution commission, Great Britain.

See Great Britain. 

Robinson, H., on chemical precipitation.... 32

on sedimentation....................... 116

Rochdale, England, trickling filtration at..; 83 

Roecbling, H. A., on sewage farming........ 25

Rogers, Anne F., work of.............

Royal sewage commission. Great Britain.

See Great Britain. 

Rugby, England, sewage farm at............ 27

Russell, H. L. See Jordan, E. O., Russell, 

H. L., and Zeit, F. R.

S.

Salford, England, chemical precipitation at. 

experiments with anaerobic filters at. 

septic treatment at...............

32 

45 

118 

trickling filtration at........ 77,78,79-80,81,83

Salt Lake City, Utah, sewage farm at.

Saltley, England, sedimentation at...

Sand filtration. See Filtration, intermittent.

Sanitary research laboratory. See Sewage 

experiment station.

Saratoga, N. Y., septic treatment at.....

Saxonville, Mass., pollution of Sudbury 

River at..................

Schjoesing, T., and Muntz, A., on sewage

purification by bacteria... 

Schultz-Schultzenstein, , on sewage

Schury,

purification by bacteria......

 , experiments by, on purifi

tion processes. 

on contact process.

Schweder, -, experiments by, on pur

96

116

50,53,95

fication processes..........

Scott-MoncriefE, W. D., construction of cultivation tank by..........

on trickling nitration.............

Scott-MoncriefE trickling filter, construction 

of.........................

Screening, treatment of sewage by...

Scudder,

by40,56,87,114,115,148 

incubator test devised

109-110

Sea water, effect of, on sewage. 38,110,11:2-113,121 

IRR 185 06 11

18

35

38

94

74

93

43,45

78,83

Page. 

Sedgwick, W. T., introduction by.......... 5-9

investigations in charge of............. 6,7

work of, on sewage-purification investigations ......................... 37

Sedimentation, treatment of sewage by.... 27,

29-35, 40, 56, 74, 87, 89,90,91,92,95,

96,114,115,116-117,118,119,148,149

Self-purification of streams........... 17-20,21-23

effect on, of summer conditions......... 22

Septic process, comparison of, with chemical

precipitation................... 52

Septic tank, action in, diagram showing.... 46

advantages of........................... 52-53

closed and open, comparison of results

from................ 44-45,119-126,148

development of, at Exeter, England.... 43

effluents from, analyses of. See Analyses. 

gas production in, diagram showing.... 44

rates of treatment In................... 47,53

removal of solids by.................... 52

treatment of sewage in.................. 40,

42-53, 56, 58, 74, 88, 89, 90, 91, 92, 

93, 94, 95, 96, 117, 118, 119-126, 

127, 128,129,130,132,145,148,149 

Sewage, amount of, flowing past experiment

station......................... 98

composition of...................... 13-16,112

See also Analyses, 

disposal of, by broad irrigation. See

Sewage farming, 

by dilution. See Dilution, 

nitrogen in, and in sand-filter effluents,

diagram showing............... 130

nuisance created by, in American

rivers........................ 21,22-23

in Thames River, England......... 21,30

purification of, by contact process. See

Contact beds, 

by sand filtration. See Filtration,

intermittent, 

by trickling process. See Filtration,

trickling, 

strength of, definition of............... 107

total nitrogen in, determination of..... 108

treatment of, by anaerobic putrefaction.

See Septic tank, 

by chemical precipitation. See

Chemical precipitation, 

by septic process. See Septic tank. 

Sewage-disposal problem, history of........ 9-96"

nature of................................ 9-13

Sewage experiment station, description of. 97-105 

experiments at, plan of............... 105-107

filter house, description of............. 99-105

plans of, figures showing..... 101,102,104

foundation of........................... 6-7

grit chamber, description of............ 99

detail of, figure showing............ 100

operation of...................... 115,116

location of.............................. 97-98

papers published by.................... 7-8

plans of, figures showing .. 98, JOO, 101,102,104
162 INDEX.

Paga

Sewage farming, economic advantages of... 28-29 

practice of......... 24-29,74,90,91,92,93,94,96

rates of treatment in................ 25,26,27

Sewage of towns commission, Grpat Britain.

See Great Britain.

Sewerage systems, number of persons connected with..................... 23

Sheffield, England, contact treatment at... 67 

septic treatment at.................... 50,118

treatment in coarse filters at........... 118

Shellfish, effect on, of sewage disposal in tide

water........................... 21

Sludge, character and treatment of, from

intermittent-filtration process.. 42 

character and treatment of, from precipitation process............... 32

from septic tanks.......... 44,47,48,50-51

Smith, E. G., work of....................... 9

Smith, J., on character of septic effluent ... 121 

Solids, suspended, removal of, in septic

tank............................ 49-51

Somerset House, England, dissolved gases

in Thames River at............. 19

Sorby, H. C., on role of bacteria in sewage

purification..................... 54

South Norwood, England, sewage farm at.. 27 

Southbridge, Mass., intermittent nitration

at............................... 40,42

Spalding, G. R., acknowledgments to...... 149

work of................................. 9

Spencer, Mass., intermittent filtration at... 40,42 

Starch, oxidation of........................ 16

Stearic acid. See Fat.

Stearns, F. P., on self-purification of streams 21

Steurnagel, , on sedimentation..... 116,117

on septic process....................... 46

Stockbridge, Mass., intermittent filtration

at............................... 40,42

Stoddart, F. W., on septic process......... 125

on trickling filtration................... 82

trickling filters constructed by......... 77

Stoddart trickling filter, construction of.... 77,79

Straining, treatment of sewage by.... 117,118-119

Streams. See Rivers.

Stuttgart, Germany, contact treatment at. 74 

experiments at, on purification processes. ........................... 94

Sudbury River, Mass., self-purification of... 17,18 

Sulphite-pulp mills, waste from, effect of, on

sewage purification............. 12

Suspended solids. See Solids, suspended. 

Sutton, England, contact treatment at..... 56-57,

63,67,68,70,88,118 

sedimentation at....................... 116

septic treatment at.................. 51,88-89

T.

Talbot, C. N., construction of sewage tanks

by.............------........... 43

Tank, septic. See Septic tank. 

Technology, Massachusetts Institute of, gift 

to, for experiments on sewage 

purification, etc................ 6,8

investigations at, on effects of sewage

disposal in Boston Harbor..... 20

See also Sewage experiment station.

Page. 

Teddington, England, dissolved oxygen in

Thames River, at............... 19

Tempelhof, Germany, contact treatment at. 94 

Thames River, England, nuisance in, caused

by overload of sewage.......... 21

self-purification of...................... 18,19

See also Barking; Crossness; London. 

Thudichum, G., oncontact process......... 57

Thumm, K., experiments by, on contact

process......................... 58

on contact process...................... 59,66 .

on German sewage-disposal practice.... 94

See also Bredtschneider, A., and 

Thumm, K.; Dunbar, ,and 

Thumm, K. 

Tipton, England, trickling filtration at..... 82

T owchester, England, sewage t ank at....... 43

Trickling process. See Filtration, trickling. 

Trinidad, Colo., sewage farm at............ 96

Triple-contract treatment, results of....... 71,91

Typhoid bacilli, life of, in water............ 11

U. 

Urbana, 111., septic treatment at........... 43,95

W.

Walker, A. W. See McManus, J. H., and

Walker, A. W. 

Waring, G. E., jr., experiments by, on forced

aeration........................ 75-76

Warington, , on sewage nitrification. 38 

Wastes, industrial, pollution by............ 12,

18,27,31,33,41,50,89,93,94

Water supply, contamination of, by sewage 21 

Watson, J. D., on bacterial treatment of

sewage.......................... 36

on chemical precipitation...........^... 31,90

on contact process...................... 67

on sedimentation....................... 90

on septic process........................ 52,90

on sewage farming................... 25-26,90

on trickling filtration................... 79,83

Wauwatosa, Wis., intermittent filtration at 132 

septic treatment at............... 46,51,53,95

Webster process of sewage treatment,

description of................... 35

Wellington, England, contact treatment at. 64 

West Bromwich, England, contact treatment at......:.................. 63-64

Westboro, Mass., intermittent filtration at. 40,42 

Westend, Germany. See Charlottenburg. 

Whittaker, , on trickling filtration... 81,82 

Whittaker-Bryant trickling filter, construction of.......................... 79

Wilcox, J. E., and Reid, G., on trickling

filtration....................... 82

Wilkinson, J. B., experiments by, on purification processes................ 91

Willcomb, G. E., work of................... 9

Winslow, C.-E. A., on purification plants of

Middle West.................... 95

on septic process....................... 46,51

on trickling filtration................... 86

work of................................. 7

See also Woodman, A. G., Winslow, C-. 

E. A., and Hansen, P.
INDEX. 163

Jfage 

Winslow, C.-E. A., and Phelps, E. B., on

European sewages.............. 15-16

Wisconsin, septic treatment in............. 95

Wolverhampton, England, trickling filtration at.......................... 83,84

Woodman, A. G., Winslow, C.-E. A., and 

Hansen, P., on self-purification 

of Sudbury River, Mass ........ 18

Woody fiber. See Cellulose.

Woolwich, England, dissolved gases in

Thames River at............... 19 ' Worcester, Mass., chemical precipitation

at............................ 32-33,34

intermittent nitration at............ 140,41,42 i

septic treatment at..................... 50

sewage of ,eflect of acid-iron waste on. 12,41,50

Page.

Worcester, Mass., sewage of, strength of .. Ill 

Wrexham, England, sewage farming at.... 25-26

Y.

Yeovil, England, contact treatment at...... 73

septic treatment at..................... 51

York, England, chemical precipitation at... 91 

contact treatment at................... 63

septic treatment at..................... 91

trickling filtration at.......... 81,83,84,88,91

Z.

Zahn, C., experiments by, on contact

process ......................... 58,94

Zeit, F. R. See Jordan, E. O., Russell,H. L., 

and Zeit, F. R.
CLASSIFICATION OF THE PUBLICATIONS OF THE UNITED STATES GEOLOGICAL

SUEYEY.

[Water-Supply Paper No. 185.]

The serial publications of the United States Geological Survey consist of (1) 

Annual Reports, (2) Monographs, (3) Professional Papers, (4) Bulletins, (5) Mineral 

Resources, (6) Water-Supply and Irrigation Papers, (7) Topographic Atlas of United 

States folios and separate sheets thereof, (8) Geologic Atlas of the United States 

folios thereof. The classes numbered 2, 7, and 8 are sold at cost of publication; the 

others are distributed free. A circular giving complete lists can be had on application.

Most of the above publications can be obtained or consulted in the following ways:

1. A limited number are delivered to the Director of the Survey, from whom they 

can be obtained, free of charge (except classes 2, 7, and 8), on application.

2. A certain number are delivered to Senators and Representatives in Congress, 

for distribution.

3. Other copies are deposited with the Superintendent of Documents, Washington, 

D. C., from whom they can be had at practically cost.

4. Copies of all Government publications are furnished to the principal public 

libraries in the large cities thruout the United States, where they can be consulted 

by those interested.

The Professional Papers, Bulletins, and Water-Supply Papers treat of a variety of 

subjects, and the total number issued is large. They have therefore been classified 

into the following series: A, Economic geology; B, Descriptive geology; C, Systematic geology and paleontology; D, Petrography and mineralogy; E, Chemistry and 

physics; F, Geography; G, Miscellaneous; H, Forestry; I, Irrigation; J, Water storage; K, Pumping water; L, Quality of water; M, General hydrographic investigations; N, Water power; O, Underground waters; P, Hydrographic progress reports. 

This paper is the fifteenth in Series L, the complete list of which follows (WS= 

Water-Supply Paper):

SERIES L, QUALITY OF WATER.

WS 3. Sewage irrigation, by G. W. Rafter. 1897. 100 pp., 4 pis. (Out of stock.)

WS 22. Sewage irrigation, Pt. II, by G. W. Rafter. 1899. 100pp., 7 pis. (Out of stock.)

WS 72. Sewage pollution near New York City, by M. O. Leighton. 1902. 75 pp., 8 pis.

WS 76. Flow of rivers near New York City, by H. A. Pressey. 1903. 108 pp., 13 pis.

WS 79. Normal and polluted waters in northeastern United States, by M. O. Leighton. 1903. 192 pp.

15 pis. 

WS 103. Review of the laws forbidding pollution of inland waters in the United States, by E. B

Goodell. 1904. 120 pp. 

WS 108. Quality of water in the Susquehanna River drainage basin, by M. O. Leighton, with an

introductory chapter on physiographic features, by G. B. Hollister. 1904. 76pp., 4 pis. 

WS 113. Strawboard and oil wastes, by R. L. Sackett and Isaiah Bowman. 1905. 52 pp., 4 pis. 

WS 121. Preliminary report on the pollution of Lake Champlain, by M. O. Leighton. 1905. 119 pp.,

13 pis. 

WS 144. The normal distribution of chlorine in the natural waters of New York and New England,

by D. D. Jackson. 1905. 31pp., 5 pis.

WS 151. Field assay of water, by M. O. Leighton. 1905. 77 pp., 4 pis. 

WS 152. A review of the laws forbidding pollution of inland waters in the United States, second

edition, by E. B. Goodell. 1905. 149 pp. 

WS 161. Quality of water in upper Ohio River basin and at Erie, Pa., by S. J. Lewis. 1906. 114 pp.,

6 pis. 

WS 179. Prevention of stream pollution by distillery refuse, based on investigations at Lynchburg,

Ohio, by Herman Stabler. 1906. 34 pp., 1 pi. 

WS 185. Investigation on the purification of Boston sewage, by C.-E. A. Winslow and E. B. Phelps.

1900. 163 pp.

Correspondence should be addrest to

THE DIRECTOR,

UNITED STATES GEOLOGICAL SURVEY,

WASHINGTON, D. C. 

NOVEMBER, 1906.

O