Improvements in Supplying Air to Filters for the Purification of Sewage and other Waters.
Year: 1899

page_text: Date of Application, 2nd Feb., 1899
Complete Specification Left, 2nd Nov., 1899-Accepted, 27th Jan., 1900
PROVISIONAL SPECIFICATION,
Improvements in Supplying Air to Filters for the Purification of
Sewage and other Waters.
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 the purification of crude sewage and other foul waters
by bacterial action and has for its object to provide in cold weather for the
supply of warmed air to the sewage passing through the mass of filtering material
in the purification chamber in order to prevent the vitality of the micro-organisms
'on whose action the purification depends being checked or arrested.
The invention is particularly applicable to the filter forming the subject of
previous Letters Patent dated the 9th day of January 1897 No. 654, and the 4th
day of March 1897 No. 5803, and it may either be used alone or if necessary in
conjunction with the method of supplying warmed air to the filter as described in
an application for Letters Patent dated the 6th day of May 1898 No. 10427.
It is necessary to supply large quantities of air to an aerobic bacterial filter
bed such as that therein referred to, but in cold weather this air must be supplied
at a temperature above 37° Fahrenheit at or about which temperature bacterial
action becomes suspended.
The present invention consists in utilizing the superabundant internal heat of
the filter for the purpose of warming the air supplied to the filter so as to prevent
satisfactory bacterial action and nitrification being checked by access of air at
too low a temperature. This is accomplished by causing the fresh air to be
supplied to the filter to first pass through thin metal pipes traversing the mass
of the filter bed, or laid in the effluent channel, or in the enclosed area surrounding
the apertured walls of the filter, or through all or any of these localities, so as
to cause the air to become warmed before admission to the filter by the heat gene-
rated by bacterial action within the mass of the filter bed, the superabundant heat
being taken either directly from the filter bed or from the effluent coming there-
from or merely borrowed from the atmosphere of the enclosed area by which the
apertured walls of the filter are protected from cold winds. The fresh air so
warmed may be supplied directly into the air flues within the body of the filter
or to the enclosing air space.
Dated this 2nd day of February 1899.
Improvements in Supplying Air to Filters for the Purification of
Sewage and other Waters.
I, WALTER MARDON DUCAT, Colonel late Royal Engineers, of 18, Devonshire
Terrace, Hyde Park, London, W. do hereby declare the nature of this
DC17

page_text: invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:-
---
My invention relates to the purification of crude sewage and other foul waters
by bacterial action, and has for its object to provide for the supply in cold weather
of warmed air to the sewage passing through the mass of filtering material
in the purification chamber in order to prevent the vitality of the micro-organisms
(on whose action the purification depends) being checked or arrested.
The invention is particularly applicable to the filter forming the subject of
previous Letters Patent dated the 9th day of January 1897 No. 654, and the 4th
lay of March 1897 No. 5803, and it may either be used alone or if necessary in
conjunction with the method of supplying warmed air to the filter as described in
the Specification of previous Letters Patent dated the 6th day of May 1898
No. 10,427.
It is necessary to supply large quantities of air to an aerobic bacterial filter
such as referred to, but the air must be supplied at a temperature above that at
which bacterial action becomes suspended, and it is therefore necessary in cold
weather to provide means for warming the incoming air supply, the temperature
of which should under no circumstances be less than 37° Fahrenheit.
The present invention consists essentially in utilizing the heat of the effluent
for the purpose of warming the air supplied to the filter so as to prevent access
of air at such a low temperature as would check satisfactory bacterial action and
nitrification. This may be accomplished by causing the fresh air which is
to be supplied to the filter to first pass through thin metal pipes traversing the
filter bed, or laid in the effluent channel, or in the enclosed area surrounding
the apertured walls of the filter, or through all or any of these localities, so as to
cause the air to become warmed (before coming in contact with the filtering
material) by the heat generated by bacterial action, the heat being taken either
directly from the filter bed or from the effluent coming therefrom or merely bor-
rowed from the atmosphere of the enclosed area by which the apertured walls of
the filter are protected from cold winds. The fresh air so warmed may be supplied
directly to the air ducts or flues within the body of the filter or to the enclosing
air space, this depending on the particular construction of filter to which my
invention is applied.
The accompanying drawings forming part of this specification illustrate the
preferred mode of carrying the invention into practice, Figure 1 being a half
horizontal section of an aerobic bacterial filter provided with my improved means
of heating the air supply, the section being taken at different levels on planes
passing through the effluent collecting and air intake channel, whilst Figure 2 is
a similar section of a filter provided with means of heating the air supply adapted
more particularly for use in exceptionally cold situations. Figures 3 and 4 are
respectively vertical part sections (drawn to an enlarged scale) on lines 3-3
and 44 Figure 1. and Figures 5, 6 and 7 are respectively similar sections on
lines 5-5, 6-6 and 7-7 Figure 2. Similar letters of reference denote like parts
in all the figures.
Referring to Figures 1, 3 and 4, the filter is constructed of an apertured wall A
surrounding and containing the stratified mass of filtering material arranged sub-
stantially as described in the specifications of the two first Letters Patent above.
referred to. the apertured wall being surrounded externally at a distance of say
about two feet by a solid wall B which may be made double or cellular so as to
better prevent loss of heat by outward radiation. The space C between the walls A
and B is roofed over and provided with double doors d, and the upper surface of
the filter bed is also roofed over as indicated in the drawings attached to the speci-
fication of Letters Patent No. 10,427 of 1898 aforesaid.
In the construction now illustrated, the effluent is collected, previous to its
delivery outside the boundary of the filter bed, in a channel or channels e forming
the bottom of air flues E built upon the floor on which the filtering material is
laid, the floor being for this purpose sloped downwards towards the channel or

page_text: channels e from the apertured wall A whose lower portion is made solid for a few
inches in height so as to prevent the escape of effluent around the circuit of the
filter bed. In a filter of small capacity, a single passage may suffice, but usually
there would be provided two or more air flues E each extending completely across
the filter bed and having its bottom channel e inclined towards both ends from the
centre so as to discharge the effluent at both ends of the filter bed.
The construction of the air flues E is clearly shown by the cross sectional view
Figure 4, the bottom channel e sloping from either side towards the centre and
being protected from the superincumbent mass of filtering material G by side
walls and a concrete, flagged, or arched roof i. The effluent runs into the
channel through apertures h¹ formed in the lowest part of the walls h, whilst the
upper portions of these walls may be constructed of perforated bricks as indicated,
through which the air in the space above the channel e is afforded access to the
interior of the mass of filtering material G which is laid upon a bottom course of
large pebbles or other suitable material g forming a collecting stratum for the
effluent as described in the Specification of the previous Letters Patent No. 654
of 1897.
Air is admitted from outside the filter through pipes J traversing the outer
The
wall B, one such pipe being placed opposite each end of each air flue E.
pipe is provided with a "hit and miss" valve or damper whereby to regulate
the air supply. and from the inner end of the pipe J a metal pipe leads across
the space C to a delivery pipe K preferably formed of sheet metal (such as zinc)
which extends half way along the air flue E terminating midway of the flue in a
stopped end, the pipe K tapering from its junction with pipe j¹ to a diameter
such as to equalize the supply of air emitted by the pipe throughout the course of
its length as hereafter described. The bottom of pipe K is laid substantially
parallel to the bottom of the effluent channel e at a height above the latter clear
of the liquid flowing in the channel, the bottom of the pipe being perforated or
slitted at throughout its whole length. This bottom slit or opening
preferably formed by outwardly bending the edges of the metal sheet of which the
pipe is composed, the longitudinal flanges (Figure 4) thus formed serving both
to stiffen the pipe and to direct the current of air downwards upon the stream or
film of liquid flowing along the effluent channel. The pipe K may be supported
at suitable intervals by splayed legs formed of metal bars bolted at their upper
ends to the outer sides of the flanges 2, a distance washer being interposed between
the flanges so as to maintain the required width (about one quarter of an inch more
or less) of the slit kl.
is
The only fresh air supplied to the filter is that admitted through the valves j
and pipes K, and it will be apparent from the foregoing description that such air
necessarily takes up a considerable quantity of heat from the stream of effluent
flowing in each channel e since the incoming air issuing from the slit impinges
directly upon the stream of effluent at the bottom of the channel and being
deflected towards either side thereof is brought into intimate contact with the film
of effluent which trickles down the sloping sides of the channel e. Moreover the
air passing along the pipe K takes up heat by conduction through the walls of the
pipe. It will be obvious that, with a view to obtaining the best results, the
number of the air flues E and the capacity of the pipes J and K should be duly
proportioned to the quantity of fresh air required; and that the channels e should
be laid at such an inclination, and the discharge of effluent outside the filter so
regulated relatively to the quantity of crude sewage dealt with, as to ensure
that the whole of the effluent shall remain in contact with the inflowing current
of air so long as may be required to effect the desired transference of heat from
the effluent to the air.
In situations where, owing to the low temperature of the outer atmosphere or
other reason, the apparatus just described is insufficient to effect the requisite
warming of the air supplied to the filter, the modified arrangement illustrated in
Figures 2, 5, 6 and 7 may be emploved,

page_text: In this arrangement the general reconstruction of the filter bed and its outer
wall B, the disposition of the passages E, and the construction of the walls,
lateral apertures h', and roof of each such passage are the same as already
described. The channel é is however deepened as shewn clearly in the cross
sectional view Figure 6, and the stream of effluent therein is maintained at a
constant level as indicated at 1 by means of a float controlled valve m
(Figure 7) or equivalent device. About midway in the depth of the channel e is
placed on suitable supports an air chamber or trunk N of shallow flat section
so as to be completely submerged in the liquid, the width of the trunk being
slightly less than that of the channel so as to permit circulation of the effluent in
the channel in the vertical direction.
The air entering the pipe J through the valve j is led across the space C between
the walls A and B and delivered to the outer end of the trunk N by means of a
sheet metal pipe, and after traversing the length of the trunk, is delivered from
the inner end thereof by a rising pipe " into the corresponding
end of the tapering slitted pipe K which is supported clear of the liquid in
the channel e SO as to discharge the air directly on to the sur-
face of the stream of effluent in the channel e, the taper of
the pipe K being towards its stopper outer end k. The inflowing current of fresh
air is thus caused to travel in contact with the heating surfaces through a course
approximately twice as long as that provided for it in the previously described
arrangement, and has its temperature raised to a considerably greater extent.
In every case the effluent should be discharged, outside the wall B. through a
syphon pipe as indicated at p in Figures 3 and 5, so as to prevent the colder ex-
ternal air from blowing back into the enclosed space within the walls.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is:
3:1
1. Constructing filters for the purification of sewage and other waters by bacterial
action in such manner that the temperature of the inflowing air supply is raised
by transference of heat thereto from the effluent for the purpose specified.
2. In filters for the purification of sewage and other waters by bacterial action,
the herein described means of raising the temperature of the inflowing air supply,
consisting in the combination with effluent collecting channels traversing the floor
of the filter bed and constructed so as to spread out the effluent in a film or
shallow stream, of air inlet pipes slitted or apertured so as to discharge the inflow-
ing air in a thin stream on to the surface of the stream of effluent in the channels.
substantially as specified.
3. In filters for the purification of sewage and other waters by bacterial action,
the herein described means of raising the temperature of the inflowing air supply,
consisting in the combination with effluent collecting channels traversing the floor
of the filter bed, of air inlet pipes or trunks submerged in the effluent in said
channels and connecting the external air inlet openings with ducts through which
the air is delivered, for the purpose specified.
Dated this 2nd day of Navamhan 1000
A. M. & WM. CLARK,
Chartered Patent Agents.
53, Chancery Lane, London.