Improvements in the Purification of Sewage and Polluted Waters.
Year: 1896

page_text: Date of Application, 3rd Dec., 1896
Complete Specification Left, 3rd Sept., 1897-Accepted, 3rd Dec., 1896
PROVISIONAL SPECIFICATION.
Improvements in the Purification of Sewage and Polluted Waters.
I FRANK PULLEN CANDY of Ivy Bank Ashley Road Bawdon in the County of
Chester, Sanitary Engineer do hereby declare the nature of this invention to
be as follows:-
The sewage or polluted waters I will hereafter speak of as sewage.
The first part of my invention relates to improvements in screens for removing
the larger solid particles from sewage; I construct a screen of parallel bars semi-
circular or approximately so or curved in shape and I cause the sewage to pass
therethrough from the top and flow away from underneath preferably so that
almost the whole of the screen is submerged, I provide also one or more rakes or
the like attached to radial arms or mounted on the periphery of a circle or other-
wise arranged so that they can be rotated and by such rotation engage between the
bars of the said screen and so carry away the solid matter deposited thereon, I
preferably also provide a rotating brush or other arrangement as hereafter de
scribed by means of which the solid matter is swept off or discharged from the
said rakes into a depositing tray or trough and I may provide this same with a
worm conveyor. The said semicircular or curved bars I preferably make of cast
iron and form thereon projections at right angles to the length thereof by means of
which the said bars are firmly bolted together and a clear passage left for the said
rakes to pass. The teeth of the rakes I may form of a number of small flexible
rods instead of one rigid piece of material and I also preferably form with bevelled
edges that part of the bars between which the teeth of the said rakes first engage.
In order to obtain motive power to continuously actuate the said rakes I may
employ an undershot waterwheel driven by the flow of sewage or where greater
fall is obtainable I may combine a waterwheel' with the arrangement carrying
the aforesaid rakes.
Or I may mount rakes upon the periphery of an undershot water wheel, by,
preference upon the blades or buckets thereof, so arranged (the sewage entering at
one side of the screen) that the head of water obtained by the choking up of the
screen shall cause the said water wheel and rakes to revolve whereby the solid matter
deposited on the screen is carried away by the blades and rakes of the said wheel
and discharged onto a receiver. In order to obtain a good fit between the blades
of the wheel and the bars of the screen I preferably attach a strip of rubber or other
suitable flexible material to the said blades and also preferably arrange for adjust-
ment of the said rubber strip to compensate for wear. I preferably form solid iron
ends to the curve formed by the bars of the screen and thus provide a frame
within which the combined wheel and rakes work and in order to conveniently
make the wheel a good fit with the said iron ends I provide facing pieces of rubber
felt or the like thereon.
In connection with the discharge of the solid matter from the teeth of the rake
into a receiver I sometimes employ a fixed comb the teeth of which are preferably

page_text: formed of rubber stiffened by a skeleton of metal, the teeth of the said rake after
leaving the screen engage with the teeth of the said comb and thus the solid matter
is discharged from the teeth of the ruke, or I may employ a hinged scraper, with
teeth if necessary, by means of which the solid matter shall be discharged from the
teeth of the rake and from the blades of the wheel.
As a modification of the before described apparatus I sometimes mount the
aforesaid rakes upon a chain or the like in which case I may sometimes reverse
the direction of the flow of the sewage.
I sometimes combine a detritus chamber or catch pit provided with means for
removing the solids, with the before described screening apparatus. I place the
said screening apparatus in a tank so that the sewage after passing the screen shall
flow through the said tank and deposit therein the grosser solid matters; in order
to provide for the removal of the said solid matters I construct the tank with sides
sloping to the centre at which part there extends a worm conveyor or other suitable
mechanism by means of which the solid matters are conveyed to a well, preferably
separated from the said tank but connected therewith by apertures in the separat
ing wall; from this said well the solids may be raised by any convenient means for
instance by a chain and buckets. I preferably place the screening apparatus in the
centre of the said tank and cause the sewage to flow in opposite directions from thence
to the two ends of the tank and I may also provide bafflers in the tank to equalise
the flow of sewage therethrough, the bafflers may have apertures therethrough.
I sometimes provide a separate detritus chamber or catch pit furnished with similar
apparatus and arrangements for removing the sludge to that. before described in
which case I preferably provide a diaphragm to the said detritus chamber behind
which the sewage flows down and then rises through the other division and flows
away at the top. I may use the beforedescribed apparatus and arrangements to
larger settling tanks. When sufficient power can be obtained I prefer to drive the
said worm conveyor and also the said chain and buckets or the like from the water-
wheel that works the screening apparatus. I may use other means for removing
the solid matters from the aforesaid tank.
The second part of my invention relates to improvements in precipitation tanks.
Instead of taking off the effluent from a continuous flow precipitation tank in a
thin layer over a sill as is usually the case I provide at the end of the said
tank a wall with a number of suitable passages therethrough or I provide a number
of exits from the said tank which passages or exits are so regulated or arranged
that as nearly as possible an equal flow of liquid shall be discharged from the
tank through each said passage or exit; by this means a much more even or
diversified flow of sewage is obtained throughout the tank. The said perforated
wall or number of exits from the tank preferably extends the whole width of the
tank and down to within two feet or so of the bottom of the said tank. When
I provide a number of exits as before mentioned from the precipitation tank I
preferably bring them up so that they discharge into a common channel and provide
each exit with a convenient means whereby the discharge from the same can be
regulated.
I sometimes also provide a similar arrangement to this before mentioned for
inlet of the sewage into the tank.
The third part of my invention relates to improvements in filters.
I place a layer or layers of gravel and coke or other suitable filtering material or
material of a suitable size or sizes in a tank or the like and pass the liquid to be
filtered through the filtering material in a lateral direction, the said filtering
material does not entirely fill the tank at each end thereof but I so place it that
there is an open space at each end by means of which the liquid can have free access
to and exit from the said layer of filtering material, for example I place a grid
across the said tank a short distance from each end thereof which grid both
the said open spaces and also serves to keep the filtering material within its proper
procures
limits; instead of an open space I may use large pebbles stones or the like.
I provide one or more exits from the bottom of the filter, (separate from the

page_text: filtered effluent exit) by means of which the filtering material may be flushed and
emptied of water, I preferably place the said exit or exits for flushing at the inlet
end of the filter and preferably slope the floor of the filter upwards from the inlet
end and preferably arrange that the sewage does not pass through the bottom part
or stratum of the filter when the same is working so that a quiescent part is provided
into which any solids that settle may remain until flushed out.
After the liquid has passed through the filtering material it flows away over or
through an exit or exits provided therefor and situated at a suitable height. I
sometimes leave open spaces in the filtering material sometimes so arranged that
solid matters may settle therein and be discharged therefrom. I sometimes form
one or more depressions or gutters in the floor of the filter and provide each such
with a discharge or discharges for the purpose of obtaining a more effectual
flushing of the filtering material, I may also provide dwarf walls from or at the
top of the said depressions or gutters.
In order to aerate or flush the filter I preferably provide automatic arrangements.
When I wish to aerate at fixed intervals of time I preferably provide a well or the
like into which a portion of the filtered sewage runs and the overflow from which or
a portion thereof when the said well is full discharges into a vessel connected with
the inlet and outlet valves by means of the fall of which vessel the said valves are
caused to open or close as may be desired, the said vessel empties itself after a
certain lapse of time, whereupon the valves resume their previous positions;
when I wish to flush or aerate the filter after the same has become choked up to a
predetermined extent I prefer to arrange that the extra head required to then pass
the sewage through the filtering material shall cause liquid to flow into a similar
or the same vessel as before mentioned.
I also prefer to arrange so that I may throw out of work a part or parts of the
filter bed and keep the remainder at work, I may arrange to do this automatically.
By using a very shallow layer of filtering material and thus exposing a large area
to the light and air I obtain conditions very favourable to the growth of alga
or other beneficent micro organisms and obtain results which can hardly be
obtained by other means.
I sometimes arrange to work one or more filter beds so that the water level
therein shall rise and fall and thus obtain constant or frequent aeration. I
prefer to effect this automatically and to work two beds in connection so that the
same flow shall or may be always passing through the two beds. For example I
provide one or more exits for filtered effluent from the filter bed, such exit or exits
may be either in the shape of a slot or of a round hole (preferably provided with
arrangements to regulate the exact amount of flow therefrom and preferably extend-
ing from the bottom of the filter bed upwards to the top) and are so arranged that
when a certain amount of sewage is turned into a filter bed (empty of water) the
same shall gradually fill up to a certain height, filtered sewage discharging from
the filter during this operation, the sewage is then, immediately or after a period
of time, shut off from the bed for a time so that the bed shall drain and crate,
when this has been sufficiently accomplished the said filter bed is started working
again, and so on. The automatic arrangements I prefer to use in connection with
the working of the said filter bed consist of one or more vessels arranged to fill
from one or more overflows and to empty as required and so open or close one or
more valves which may be weighted. I may arrange each tank to work indepen-
dently instead of in pairs.
I sometimes use more than one filter as before described connected together, and
sometimes as a modification employ divisional walls across the filter bed so that the
sewage takes a serpentine motion therethrough, in order to arrange for flushing or
erating such a bed I arrange discharges or connections where required, I may use
automatic valves such as flap valves in relation to this.
Dated this second day of December 1896.

page_text: Improvements in the Purification of Sewage and Polluted Waters.
I FRANK PULLEN CANDY of Ivy Bank Ashley Road Bawdon in the County of
Cheshire Sanitary Engineer 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; -
The sewage and polluted waters I will hereafter speak of as sewage.
The first part of my invention relates to improvements in screens for removing the
larger solid particles from sewage; I construct a screen of parallel bars curved in
shape and I cause the sewage to pass therethrough from the top and flow away from
underneath I provide also one or more rakes or the like attached to radial arms or
mounted on the periphery of a circle or otherwise arranged so that they can be rotated
and by such rotation engage between the bars of the said screen and so carry away the
solid matter deposited thereon. In connection with the discharge of the solid
matter from the teeth of the rake into a receiver I employ a fixed comb, the teeth
of the said rake after leaving the screen engage with the teeth of the said comb
and thus the solid matter is discharged from the teeth of the rake. The said
curved bars I preferably make of cast iron and form thereon projections by means
of which the said bars are firmly bolted together and a clear passage left for the
said rakes to pass.
Figure 1 of the accompanying drawings illustrates in cross section a ourved
screen with two rakes, 1 is the curved bar of the screen and 2 the projections
thereon by means of which the bars are bolted together and kept at the required
distance apart, 3 are arms carrying rakes 4 which engage between the bars of the
screen; 5 is the shaft to which the arms are fastened, 6 indicates a crank by means
of which the said arms and rakes are worked, 7 is the comb fixed to the support 7 a
which comb engages with the teeth of the rake and discharges the solid matters
into the tray 8 from which it can be conveniently removed, the dotted lines 9
indicate a cast iron end to the screen with a bearing to carry the shaft 5 and 10
represents an overflow passage to operate in case of neglect: the sewage enters
at 11 and flows away at 12 the arrows indicating the direction of the sewage flow.
13 represents the floor of the sewage carrier in which the screen is placed: no
sewage should be able to pass between the front of the screen & the floor of the
sewage carrier, the dotted lines 14 indicate the normal level of the sewage in the
screen, 17 is a bar supporting the end of the screen.
The size of the screen will of course vary with the quantity of sewage to be dealt
with and it may be greater in length than the diameter of the arms; a suitable
size for such a screen to deal with a flow of about 100,000 gallons of sewage per
24 hours would be one having arms about four feet diameter and the screen about
six feet long. I do not limit myself to two arms carrying rakes and when I use
more than one arm I may arrange the rakes so that each shall clean a portion only
of the length of the screen; I do not either limit myself to the position of the comb
as shown in the drawings. As an alternative I may pass the sewage through
the length of the screen instead of through the diameter as shown in which case the
curved bars would both be brought above the sewage level and one end of the
screen be open to receive the sewage while the other end would be closed to retain
the solid matters in the screen. I may arrange to actuate the shaft which causes the
rake or rakes to revolve by any power available.
In order to obtain motive power to continually actuate the said rakes I may em-
ploy an undershot waterwheel driven by the flow of sewage or where fall is avail-
able I may combine a waterwheel with the arrangement carrying the aforesaid
rakes. In order to obtain a good fit between the blades of the wheel and the

page_text: bars of the screen I preferably attach a strip of rubber or other suitable flexible
material to the said blades and also preferably arrange for adjustment of the
said rubber strip to compensato for wear. I preferably form solid iron ends to the
curve formed by the bars of the screen and thus provide a frame within which the
combined wheel and rakes work and in order to conveniently make the wheel a good
fit with the said iron ends L provide facing pieces of rubber felt or the like thereon.
Figure 2 illustrates in cross section a screen in which a water wheel
is combined with the rakes. The same figures where used illustrate the
same parts as in the preceeding Figure; 3 being not merely arms, but blades of
a waterwheel; 15 is a solid frame of iron curved to the radius of the ends of the
rakes and 16 are strips of rubber or leather hinged or mounted as shown so as to
seal or cover over the spaces between the teeth of the rakes and thereby enable the
blades to which the rakes are attached to better hold the sewage, and also to be
sufficiently flexible to allow the rakes to easily pass through the screen; the head
of sewage on the blades forces them round and the sewage escapes through the
screen 1 and flows away at 12 as indicated by the arrows; the side ends of the
blades 3 require to be a close fit against the sides 9 of the screen and for that
purpose I prefer to provide them with strips of rubber, leather, felt or the like.
The solids retained by the bars of the screen are as the wheel rotates continually
carried away by the rakes from which they are discharged by means of the comb
on to the receiver. I may omit the parts 16 in which case the rakes must choke up
before the wheel will move. I provide air holes to the water wheel as required.
I do not limit myself to the exact details as shown on the drawing which it is
evident may be varied without departing from the scope of my invention.
As a modification of the before described apparatus I sometimes mount the afore-
said rakes upon a chain or the like. Figure 3 illustrates a modification with the
rakes attached to a chain. The same figures (where used) indicate the same parts as in
the previous Figures: 18 is the chain to which the rakos are attached, 19, 20 and 21
are three sprocket wheels around which the chain passes, the wheels 21 are revolved
by means of a crank attached to the shaft carrying them (or otherwise revolved by
power) when it is required to clean the screen. There is one chain at each side of
the screen each chain having its three sprocket wheels, the two wheels 21 being
connected by a shaft, the teeth are carried on a bar attached to the two chains.
This arrangement is convenient when it is required to raise to ni considerable height
the solid matter intercepted by the screen.
The second part of my invention relates to improvements in precipitation tanks.
Instead of taking off the effluent from an ordinary reetangular continuous flow
precipitation tank in a thin layer aver a sill as is usually the case I provide at the
end of the said tank a wall with a number of passages therethrough on I provide a
number of exits from the said tank which passages or exits are so regulated or
arranged that as nearly as possible an equal flow of liquid ahall be discharged
from the tank through each said passage or exit: by this means a much more even
or diversified flow of sewage is olsained throughout the tank. The said perfona-
tions in the wall or number of exits from the tank preferably extends the whole
width of the tank and down to within two feet or thereabouts of the bottom of the
said tank. When I provide a number of exits as before mentioned from the pre-
cipitation tank I preferably bring them up so that they discharge into a common
channel and I provide each exit with a convenient means whereby the discharge
from the same can be regulated.
Figure 4 illustrates in longitudinal section the end of a tank provided with a
wall having a number of passages therothrough through which the sewage shall
flow, it will be understood that these passages extend for the whole length of the
wall at distances of about two or three feet apart. 22 is the tank and 23 the end
wall thereof over the top of which the treated sewage flows into the conduit 24,
25 is the water level of the tank 26 is the wall having passages 27 therethrough,
these passages may be formed by building lengths of stoneware pipes in the wall
or may be left out as pigeon holes in which case they should be finished off

page_text: smooth, 28 is the space between the passaged wall and the end of the tank, the
lower part of this space may be filled up below the dotted line.
Figure 5, illustrates in longitudinal section a tank provided with a number
of exits therefrom, 22 is the tank, 25 the water level in the same, 23 the end wall
thereof and 27 the exits for treated sewage from the tank, 24 is the conduit into
which the exits deliver; the tops of the exits may be furnished with an adjustable
cover by means of which the quantity of effluent discharged from each can be
regulated; the exits can be conveniently formed of stoneware pipes and they
extend along the end wall of the tank at distance of about two or three feet apart.
I sometimes provide a similar arrangement to that illustrated in figures 4 and 5
for inlet of the sewage into the tank, the flow through the "passages" or "exits"
being the reverse to that indicated in the said figures.
The third part of my invention relates to improvements in filters. I place a
layer or layers of gravel and coke or other suitable filtering material or materials
of a size varying from about one and a half or one inch diameter to about
the one sixteenth of an inch diameter in a tank or receptacle and
pass the liquid to be filtered through the filtering material in a lateral
direction; the said filtering material does not entirely fill the tank at each
end thereof but I do so place it that there is an open space at each end by means
of which the liquid can have free access to and exit from the said layer of filtering
material, I find a space of about. six inches or nine inches wide is suitable; for
example I place a grid across the said tank at a distance of about six inches from
each end thereof which grids both procure the said open spaces and also serve to
keep the filtering material within ita proper limits, the grid may be either an iron
grid or formed by a pigeonholed wall or otherwise conveniently arranged in well
known manner instead of an open space I may use large pebbles stones or the like
for instance pebbles or stones of about the size of ones fist, that is about three inches
diameter, forming a laver about nine inches or twelve inches wide at each end
of the tank, I do not however consider this arrangement which is illustrated in
Figure 7 as effective as the other. I provide one or more exits from the bottom
of the filter, separate from the filtered effluent exit by means of which the filtering
material may be emptied of water or flushed, I preferably place the said exit or
exits when used for flushing at the inlet end of the filter and preferably slope the
floor of the filter upwards from the inlet end. After the liquid has passed through
filtering material through which it passes and flows ovenly through the grid 28 a at
therefor and situated at a level slightly below the top of the filtering material,
for example two or three inches below.
Figure 6 illustrates in longitudinal section a lateral filter provided with grids
or their equivalents 28 and 28 a at inlet and outlet ends and a high level exit 29
over which the filtered sewage flows, 30 is the conduit feeding sewage into the
space 31; the sewage flows evenly through the spaces in the grid 28 into the
filtering material through which it passes and flows evenly through the grid 28 a at
the exit end into the space 31a and over the wall 29 and so away; 32 is
a valve through which the filter is emptied of sewage for neration or cleaning.
The filter may be of any convenient size; I find that from 500 to 1,000 gallons of
sewage per 24 hours per square foot of cross sectional filtering area may be passed
through the filter when dealing with liquid such as an ordinary precipitated tank
effluent, I should construct the bed of about twenty feet in length or more; if
a fauler liquid such as crude sewage were to be filtered the rate of filtration should
be slower and the filter longer and similarly if a considerable amount of purification
were required. The size of the filtering material will vary according to the nature
of the sewage; for crude sewage the material at the inlet end of the filter
should be about one and a half or one inch diameter reduced down
gradually until at the outlet end the material is about one sixteenth
of an inch diameter: if the sewage has been settled or precipitated
the largest material need not be more than about half an inch diameter reduced
down at the outlet end as before mentioned. The material at the inlet end of the

page_text: filter should be higher than at the outlet end, owing to a head of water being re-
quired to cause the sewage to pass at a comparatively quick speed through the
material, a head of about one inch to two inches per ten feet I find sufficient for
ordinary speeds.
I sometimes leave open spaces in the filtering material sometimes arranged that
solid matters may settle therein and be discharged therefrom. Figure 8 illus-
trates the open space 33 between the filtering material 34, a gutter 35 is provided
furnished with a discharge pipe 36 through which any deposit that settles may be
removed, or the material flushed, 37 are ledges, preferably spaced, to prevent the
material from tending to fall into the gutter; the function of this said open space
is to prevent the bed from requiring washing or cleaning as often as would other-
wise be required.
I sometimes form one or more depressions or gutters in the floor of the filter
and provide each such with a discharge or discharges for the purpose of obtaining
a more effectual flushing of the filtering material, such gutters or depressions being
formed in the first part of the filter as there the bulk of the solids will be deposited,
if the sewage to be filtered is comparatively clear, such for instance as ordinary
tank effluent these gutters would not be required.
Figure 9 illustrates in longitudinal section the inlet part of the filter having
the floor sloped upwards at 38 and also with a depression at 40 and provided with col-
lecting channels 39 and 39 a having outlet or outlets thereto (not shown) by means of
which the filtering material can be flushed. I do not limit myself to the particular
details for flushing as illustrated for instance I may provide openings at the bottom
of the grid 28 and flush the material above 38 by draining the space 31 or I may
use one only of the arrangements shown.
I also prefer to arrange so that I may throw out of work a part or parts of the
filter bed and keep the remainder at work.
Figure 10 illustrates in plan and Figure 11 in longitudinal section method of
throwing part of the filter out of work without affecting the working of the
remainder; 31 is the feed space serving the part of the filter 43, 28 and 286 are
the grids, 316 the collecting space, 41 is a divisional wall provided with apertures
therethrough closable by valves at will as shown; 31 c is the feed space serving
the part of the filter 44, 28 c and 28 d are the grids, 31 d the collecting space, 41 a a
divisional wall similar to 41, 31e is the feed space serving the remainder of the
filter 45 through the grid 28 e, 46 are conduits having valves thereon and connecting
the part of the bed 43 with the part 45, 42 is the sewage conduit arranged with
sluices so that the sewage may be turned either into 31 or 31 c; when it is wished
not to work the part 44 but to work 43 and 45, the sewage is turned into 31, the
valves of the apertures through the wall 41 are closed and the valves on 46 opened;
when it is desired not to work the part 43 but to work the parts 44 and 45 the
sewage is shut off from passing into 31 and turned into 31 c and the valves on 46
closed; the apertures in the wall 41 enable 43, 44 and 45 to be worked together,
if this were not required they could be omitted; draining outlets not shown are
provided from 43 and 44. In a similar manner I may arrange to cut the bed up
into as many divisions as required any of which may be thrown out of work without
affecting the others. I do not limit myself to the exact details shown in Figs 10
and eleven as they may obviously be modified without departing from the principle
of my invention."
When the filtering material cr part thereof has become dirty beyond the practical
cleansing powers of the flushing and aerating I remove the same and wash and re-
place it or employ fresh material.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is.
1 The construction and arrangement of screening apparatus substantially as
described and illustrated with reference to Figure 3.

page_text: 2 The construction and arrangement of screening apparatus substantially as
described and illustrated with reference to Figure 2.
3 The construction and arrangement of screening apparatus substantially as
described and illustrated with reference to Figure 3.
4 The construction of and arrangement for the exit of liquid from a settling
tank substantially as described and illustrated with reference to Figures 4 and 5.
5 The construction of and arrangement for the inlet of liquid into a settling
tank substantially as described.
6. A Lateral filter provided, with means for evenly delivering the liquid to be
treated to the filtering material at the inlet end of the filter, and for evenly
collecting the filtered liquid at the outlet end of the filter, and with a high level
exit for the filtered liquid, and with a low level exit for draining the filter when
required.
7 The construction and arrangement of a filter bed substantially as described
and illustrated with reference to Figures 6 and 7.
8 In a filter bed the construction and arrangement substantially as described and
illustrated with reference to Figure 8.
9 In a filter bed as described means for flushing material therein substantially
as described and illustrated with reference to Figure 9.
10. In a filter bed as described the construction and arrangement whereby a
part or parts may be thrown out of use substantially as described and illustrated
with reference to Figures 10 and 11.
Dated this second day of September 1897.