IMPROVEMENTS IN TREATING SEWAGE IN ORDER TO OBTAIN VALUABLE PRODUCTS THEREFROM
Year: 1868

page_text: LETTERS PATENT to Gavin Chapman, of Glasgow, in the County of
Lanark, North Britain, Manufacturing Chemist, for the Invention
of "IMPROVEMENTS IN TREATING SEWAGE IN ORDER TO OBTAIN VALUABLE
PRODUCTS THEREFROM."
Scaled the 9th April 1869, and dated the 20th October 1868.
•
PROVISIONAL SPECIFICATION left by the said Gavin Chapman at the
Office of the Commissioners of Patents, with his Petition, on the
20th October 1868.
L, GAVIN CHAPMAN, of Glasgow, in the County of Lanark, North
Britain; Manufacturing Chemist, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN TREATING SEWAGE IN ORDER TO OBTAIN
VALUABLE PRODUCTS THEREFROM," to be as follows:-
This Invention has for its object to obtain valuable products-from
sewage whilst obviating the pollution of rivers by it, and it consists,
firstly, in treating the sewage with caustic lime or other suitable alkalino
Cagent in order to precipitate solid matters to be used as manure, and to

page_text: set free ammonia; secondly, in heating the separated liquid with the
ammonia in solution in order to distil off and thereby recover the
ammonia. In using the lime care is taken to avoid excess of it, which
may be most easily managed by passing fresh quantities of sewage over
the precipitates until the lime in them appears to be well exhausted.
After the precipitate has subsided the supernatant liquid containing
ammonia in solution is put into a large shallow still wherein it is heated,
and in connection with which there is any known suitable condensing
arrangement. Fresh supplies of the liquid are used as the medium
for cooling the condenser so as to utilise the heat. The liquid is kept
boiling for a few minutes to insure the distilling off of most of the
ammonia, after which it is discharged, and it may be made to give up
some of its heat to the succeeding charge by means of well known
apparatus like a surface condenser. The ammonia may be taken from
the apparatus as liquor ammonia, and be re-distilled to concentrate it,
after which it may be mixed with acid to form a salt and be concentrated
and crystallised.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Gavin Chapman in the Great Seal Patent Office
on the 19th April 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GAVIN
CHAPMAN, of Glasgow, in the County of Lanark, North Britain, Manu-
facturing Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twentieth day of October, in the, year
of our Lord One thousand eight hundred and sixty-eight, in the thirty-
second year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Gavin Chapman, Her special licence that I,
the said Gavin Chapman, my executors, administrators, and assigns, or
such others as I, the said Gavin Chapman, my executors, administrators,
and assigns, should at any time agree with, and no others, from time to
time and at all times thercafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend, within the
United Kingdom of Great Britain and Ireland, the Channel Islands, and
Isle of Man, an Invention for "IMPROVEMENTS IN TREATING SEWAGE IN ORDER

page_text: TO OBTAIN VALUABLE PRODUCTS THEREFROM," upon the condition (amongst
others) that I, the said Gavin Chapman, my executors or administrators,
by an instrument in writing under my, or their, or one of their hands
and seals, should particularly describe and ascertain the nature of the
said Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Scal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
.[
NOW KNOW YE, that I, the said Gavin Chapman, do hereby declaró
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement in writing, that is to say:-
My said Invention has for its object to obtain valuable products from
sewage whilst obviating the pollution of rivers by it, and it consists of a
system comprising the precipitation of solid matters by means of lime or.
other alkaline agent, and the subsequent separation of the ammonia by
distillation. I am aware that lime or other alkaline agent has already
been used for precipitating the solid constituents of sewage, and also
that ammonia has been separated from more or less dilute solutions by
distillation, and I make no claim respecting either of these processes.
by itself; but my Invention consists essentially of a novel combination.
of consecutive processes forming an efficient and economical general
system, and I proceed to particularly describe the details of this system,
premising that some of them are susceptible of obvious modifications
without departing from the peculiar characteristics of my Invention.
For the purpose of most advantageously carrying out my Invention
I prefer that the portion of the ordinary sewage comprising the excreta
from waterclosets, urinals, and the like be kept separate from the bulk
of drainage water which enters ordinary sewers either by means of
separate sewers or drain pipes or otherwise. The richer sewage. thus
obtained I collect in large tanks or reservoirs wherein it is retained.
during from three to four days, or until it has become decomposed, the.
decomposition being hastened by always leaving in the tanks a quantity
of previously decomposed sewage and by maintaining the sewage at a
temperature of from 70 to 80 degrees Fahrenheit. When decomposed
the sewage is transferred to precipitating tanks wherein hydrate of lime
or other alkaline agent is added to it, excess of lime being avoided in
order not only to economise the lime, but also to render the resulting

page_text: precipitate more suitable for manure. The lime causes the organic
matters held in suspension to be deposited and at the same time sets
free the ammonia. After settling the clear liquor is run off into a large
shallow boiler or still which forms one of a series of eight or other
convenient number. These boilers are arranged in a circle or otherwise
in convenient proximity, and are connected with each other by pipes,
each pipe leading from the top of one to a perforated coil disposed below
the liquid level in the next. Each boiler is also fitted with pipe cons
ncotions for filling and emptying, and there are also a set of pipe
connections for admitting steam from a common steam boiler to the
porforated coil of each, and another set leading from the top of cach to
a vessel containing sulphuric acid. The filling and emptying pipes are
connected to a heat transferring apparatus made like any convenient
known kind of refrigerator in use in breweries, and in which the fresh
liquor passing in one direction takes up the heat of exhausted liquor
passing in the opposite direction, the transfer of heat taking place
through thin metallic partitions which separate the two currents. The
various pipe connections are provided with stop-cocks or valves, and the
cycle of operations is as follows, the boilers or stills being supposed to be
numbered in order from 1 to 8:-The fresh steam from the steam boiler
is passed into the coil of No. 1, and the steam rising therein with the
ammonia it carries with it, passes into the coil of No. 2, and so on to
No. 6. The steam from No. 6 being highly charged with ammonia
passes into the sulphuric acid and causes the formation of sulphate of
ammonia. Whilst this is taking place No. 7 is being filled with fresh
liquor, and No. 8 is being emptied. When it is considered that the
ammonia in No. 1 has been driven off as completely as practicable the
stop-cocks of Nos. 1, 2, 6, 7, and 8 are so altered that the actions in
Nos. 2, 7, 8, and 1 become the same respectively as those previously
going on in Nos. 1, 6, 7, and 8; in other words, No. 2 taking the office
of No. 1, and the others correspondingly changing; then when the
liquor in No. 2 is freed from 'ammonia No. 3 is made to take the office
originally of No. 1, and the others take it afterwards in regular suc-
cession. In this way the steam always passes through six boilers, and
as the liquor in each boiler becomes poorer in ammonia it is acted upon
by steam containing less, and therefore the better able to extract it from
the more dilute solution. With these arrangements the fuel will be
economised to the utmost, whilst with the same view loss of heat by
radiation may be reduced to a minimum by encasing the boilers or stills

page_text: with non-conducting materials, steam will be given off from the vessel
containing sulphuric acid, and may be utilised in any convenient way,
as for example, for heating the fresh sewage for the purpose of hastening
its decomposition, or the fresh sewage may be heated for that purpose by
passing it along a tunnel through which the fire gases from the steam
boiler furnaces may be made to proceed on their way to the chimney
stalk. I prefer to work with a low pressure of steam in the steam boiler,
having the pressure raised only so high as is in practice found to be
necessary for causing steam to blow through the entire series of boilers
or stills in operation. It will be desirable to test the liquor in the boilers
or stills before finally running it off to ascertain not only whether or not
all the free ammonia has been driven off, but also whether the decom.
position has been complete; this testing is to be done by adding a little
milk of lime to a small quantity of the liquor, and if this shows that the
decomposition has not been complete a suitable quantity of milk of lime
must be added to the liquor in the boiler, which will effect the complete
decomposition on the boiling being continued. The milk of lime may be
introduced into the boilers or stills either by a pump or by a filling pipe
of a height to contain a column of liquid equivalent to the pressure in
the boilers or stills.
In witness whereof, I, the said Gavin Chapman, have hereunto
set my hand and scal, this Seventeenth day of April, in the year
of our Lord One thousand eight hundred and sixty-nine.
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
GAVIN CHAPMAN. (L.s.)