Improvement in the Method of, and Apparatus for, Purifying Water, Sewage, and other Foul Liquids.
Year: 1897

page_text: Improvement in the Method of, and Apparatus for, Purifying
Water, Sewage, and other Foul Liquids.
I, WALTER MARDON DUCAT, Colonel late Royal Engineers, of 13, Devonshire
Terrace, Hyde Park, London, W., do hereby declare the nature of this Invention
to be as follows:-
My Invention relates to a method of, and means for, purifying water, sewage,
and other foul liquids, by biological action in a filtering medium and it has for its
object to ensure the continuous aeration by natural means of the filtering medium and
consequently of the liquid passing through it and actually undergoing the process, of
purification.
To this end the Invention consists essentially in constructing the sides of the
structure containing the filtering medium of openwork whether in the form of gratings,
honeycombed brickwork, tiles, perforated metal, or other apertured construction
affording access for the ambient air to the filtering medium so as to permit of the
air penetrating the pores or interstices thereof under the exhaustive action due to
the motion of the water between and through the particles of the filtering medium.
To ensure this action, the filtering medium would not be submerged but the liquid
to be purified would be supplied at a rate so commensurate with the rate of flow
through the filtering medium that the latter shall not be overcharged with liquid.
The apertured sides of the structure should be so constructed that the apertures shall
have an upward inclination from the interior to the exterior or should be lined or
protected internally by means such as to prevent the escape either of the filtering
medium or of the liquid whilst permitting the ingress of air.
When sand or other pulverulent material is used, a botton drainage layer of coarse
material would be provided for permitting the escape of the water whilst preventing
the carrying off of the fine particles of filtering material. By the intimate and con-
tinuous aeration thus afforded, the biological action will be rendered more effective
for the purposes of nitrification and consequently the process of purification will be
accelerated and greater purity of the effluent will be obtained.
Dated this Oth day of January 1907
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.

page_text: Improvement in the Method of, and Apparatus for, Purifying
Water, Sewage, and other Foul Liquids.
I, WALTER MARDON DUCAT, Colonel late Royal Engineers, of 13 Devonshire
Terrace, Hyde Park, London, W., do hereby declare the nature of this Invention
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
This Invention relates essentially to the purification of raw, untreated, sewage and
other foul liquids by bacterial action but is applicable to the purification of water
generally and it has for object to ensure the continuous aeration by natural means of
a continuously acting filter-bed throughout its mass whereby bacterial action will be
rendered more effective for the purpose of "nitrification" and consequently the
process of purification will be accelerated and greater purity of the effluent will be
obtained.
Heretofore filter-beds, whether continuous or intermittent in action, have usually
been submerged, that is to say covered with the liquid to be purified, so that whilst
the filter was in operation access of air to the filter was not possible. Such access of
air was only possible during the periods of rest when the system of intermittent
filtration was adopted, and as the surface only of the filter-bed was exposed to the
air long periods of rest were required, during which periods the filter was of course
standing idle. The superficial aeration thus intermittently obtainable is insufficient
to maintain the bacteriological efficiency on which the purifying action depends, it
having been discovered that for the purification of sewage and other foul liquids a
continuously maintained high degree of aeration is necessary to supply the oxygen
required, the filter-bed having for its principal function to act as the nidus for the
microbes by which the organic impurities are destroyed and not as a mechanical
strainer.
According to my Invention the continuous aeration throughout the whole mass of
a continuously acting filter-bed is ensured by natural means and in such a manner
that the aeration is directly brought about by the working of the filter itself so that
being entirely independent of adventitious aid the aeration is rendered continuous
and the purifying action is maintained at so high a degree of efficiency that the
working of the filter may be continued without intermission for an indefinite period,
the whole of the solid matters suspended in the sewage being disposed of by bacterial
action so that no renewal or cleaning of the filter-bed is required.
This result is attained by providing for the continuous permeation of the ambient
air through the midst of the mass of the filter-bed, the penetration of the
air into the interstices being produced by the exhaustive action due partly to the
vacuum produced by the absorption and entry into combination with organic matter,
of the oxygen of the air, and partly to the motion of the liquid through the filter-bed,
this exhaustive action being rendered constant by so regulating the rate of supply of
the liquid relatively to the rate of flow through the filter-bed that the latter shall
never be fully charged with liquid and consequently shall never be submerged.
The invention will be described with reference to the accompanying drawings
forming part of this Specification wherein Figure 1 is a half plan, half horizontal
section, of a filter the section being taken on two different planes. Figure 2 is a
vertical section. Figure 3 is a part elevation of one of the apertured walls. Figure 4
is an enlarged sectional detail view of one of the sewage supply troughs. Figure 5
is a part vertical section shewing a modified means of aerating by lateral admission
of air.
The walls A of the filter are apertured or constructed of open-work, such as honey-

page_text: combe brickwork, or preferably of superposed rows of earthenware pipes a laid in
cement, the walls thus openly constructed throughout their whole length and height
being erected between supporting pillars of solid work. The pipes a traverse the
thickness of the wall and are preferably laid in a downwardly inclined direction from
the outside to the inside of the wall so as, whilst confining the filter-bed, to afford
the most ample access for the ambient air thereto, the filter-bed being thus practically
exposed to the air over almost the whole area of its four sides as well as over its upper
surface. In order to provide for the rapid permeation of the air through the mass of
the filter-bed, strata of very coarse material are interposed between the adjacent
strata of finer material and in these very coarse strata there may be laid pipes a¹
forming open jointed continuations of certain of the air inlet pipes a and serving to
effect an equable distribution of the air through the mass. At the bottom of the
filter is a drainage layer of large pebbles in which there may be laid open-jointed
pipes B leading to outlets b in the walls A discharging into a gutter b¹ by which the
effluent is carried away.
In order to render continuous the exhaustive action by which the air is caused to
be drawn into the mass of the filter the rate at which liquid to be purified is supplied.
to the filter-bed must be so limited as compared with the rate of flow through the
mass that the surface of the bed shall never be submerged and the mass shall never
be saturated to such an extent as to produce à head of liquid pressure in the chamber
which would tend to cause the liquid to run out at the perforated sides before it
reaches the discharge apertures b at the bottom of the chamber. The distribution of
the sewage to the filter should be as uniformn as possible and may be effected
preferably by allowing it to overflow the sides of troughs D extending over the filter-
bed and supplied through spouts e from a main trough E, the troughs D being
provided with means of adjustment as at d whereby they may be accurately set at
such a slight inclination that the overflow from the troughs D will be as nearly as
possible uniform over their whole length.
The filter-bed itself may be of any suitable arrangement of materials but it is.
preferred that it should be formed of strata progressively graduated of decreasing
coarseness from the uppermost to the lowermost, which arrangement forins the subject
of another application for Letters Patent dated the 4th day of March 1897 No. 5803.
The filter-bed is composed preferably of clean washed gravel for instance or of pebbles,
punice stone, stone chips, or equivalent in sterial not liable to become disintegrated
by the action of the air and water. The uppermost stratum F should be about two
feet thick and of a grade corresponding to about one inch diameter, the intermediate
strata F, F, being each about one foot thick and of grades respectively of about
half an inch and a quarter of an inch diameter; and the bottom stratuin F3 being of
a grade corresponding to about one-eighth of an inch diameter and of a thickness
depending on the impurity of the sewage and the degree of purification required.
Although these dimensions are indicated as suitable for purifying sewage, I would
have it understood that they are in no way obligatory and may be varied according
to circumstances.
Instead of, or in addition to, the walls of the filter chamber being apertured the
lateral aeration of the filter-bed might be provided for by interposing between the
walls and the filter-bed a vertical stratum or lining wall A¹ (Figure 5) of such very
coarse lumps of material that the air will have free passage between them from above,
the liquid being distributed only over the surface of the filter-bed proper and that at
such a limited rate that there is never any head of pressure within the filter-bed.
Air tubes a' may extend from this air inlet wall through coarse intermediate strata
as before.
As however the tubular or apertured construction of the walls before
described is sufficient for the purpose, and as the interposition of the coarse lining
wall A would uselessly extend the superficial dimensions of the structure it would
not be generally adopted and is only indicated here as a possible modification.
I have illustrated in the drawings a means of protecting the filter-bed from cold
and maintaining the temperature of the mass uniform and above, say, 40° Fahrenheit.
The walls of the filter are surrounded by an air chamber G enclosed within solid

page_text: walls g and a roof, large doors g¹ being provided in the walls g for admission of air
in warm weather, which doors are closed when the external temperature falls below
a certain point. Adjoining one of the outer walls g is a chamber H communicating
with the external air and connected with the air chamber G by one or more pipes h
passing horizontally through the mass of the filter-bed so that when the external
temperature is not so low as to necessitate recourse to artificial heat the air will be
supplied to the air chamber only through these pipes and will become warmed by
the heat generated within the mass of the filter-bed by the action of the filter. In
long-continued severe frosts however, a stove in the chamber H must be used to
raise the temperature of the air before its admission to the air chamber so that air
at the proper temperature will be supplied to the filter through its perforated sides.
As above mentioned, the scope of the Invention is not limited to the treatment of
sewage which is only cited by way of example, the Invention being equally applicable
for the purification of river and other water contaminated with organic impurities,
the object of the treatment being to render such water fit for drinking.
Having now particularly described and ascertained the nature of the said Inven-
tion and in what manner the same is to be performed I declare that what I
claim is:-
1. The herein described method of producing the continuous aeration of a
continuously acting, filter for purifying sewage and other foul liquids by bacterial
action, which method consists in providing for the free admission of ambient air
throughout the whole mass of the filter-bed and limiting the supply of liquid to the
filter so that an exhaustive action will be produced by the absorption of oxygen and
by the motion of the liquid passing through the bed whereby the air will be
continuously drawn into the mass as described.
2. The herein. described method of producing the continuous aeration of a
continuously acting filter for purifying sewage and other foul liquids by bacterial
action, which method consists in providing for the free admission of ambient air
through the sides and into the midst of the filter-bed, and limiting the supply of
liquid to the filter so that an exhaustive action will be produced by the absorption
of oxygen and by the motion of the liquid passing through the bed, whereby the
air will be continuously drawn into the mass as described.
3. A continuously acting purifier or filter for purifying sewage and other foul
waters by bacterial action, having walls of tubular, apertured, or open structure or
otherwise adapted to confine the filter-bed whilst giving free continuous lateral
admission of air to the filter-bed substantially as and for the purpose specified.
Dated this 8th day of October 1807
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.