Improvements in the Filtration of Impure Waters and Sewage, and in Apparatus and Arrangements and Materials for use therein, and in Apparatus and Arrangements for use in the Precipitation of Sewage.
Year: 1892

page_text: Date of Application, 12th Oct., 1892
Complete Specification Left, 12th Aug., 1893-Accepted, 7th Oct., 1893
PROVISIONAL SPECIFICATION.
Improvements in the Filtration of Impure Waters and Sewage, and
in Apparatus and Arrangements and Materials for use therein,
and in Apparatus and Arrangements for use in the Precipitation
of Sewage.
I, FRANK PULLEN CANDY of 56 Nightingale Lane Balham in the County of
Surrey Sanitary Engineer do hereby declare the nature of this invention to be as
follows:-
The first part of my invention relates to improvements in the filtration of sewage
and impure waters: I construct the filter beds in such a manner that a current of
air can be passed through them; in carrying this into effect I form the layer or
layers of material in the filter bed through which I desire to pass the current of
air of granules of material of such a size that the air will pass therethrough when
the bed is working, the said layer or layers being connected with the air by
ventilating pipes through which the air is lead or forced; for instance I may have
such a layer as before described one foot in thickness and have inlet ventilating
pipes connected with the bottom of the said layer and exit ventilating pipes
connected with the top of the said layer, or vice versa, I prefer to use the layer of
oxidizing material (when one is employed) in the filter bed in this manner; or
1 may place a layer or layers of material of the size before indicated, of a thickness
of three or four inches I find sufficient, in. the sand or in other close laying parts
of the filter bed, and lead or force a current of air therethrough or I may obtain
the desired result in other ways.
I find that if I use coke of various sizes in place of the gravel or pebbles
generally used in filter beds I obtain better results more especially if the spaces
between the granules of coke be not filled with water that is to say if they contain
air. I obtain still better results if I coat or impregnate the coke with hydrated
ferric oxide or with a mixture of that and hydrated ferrous oxide, I may accomplish
this by soaking the coke in a strong solution of ferrous or ferric sulphate, or in a
mixture of both, letting it drain and then soaking it in an alkaline solution, such
as lime water, hydrated ferrous or ferric oxide or both will be precipitated in and
upon the coke, if I wish to oxidize the hydrated ferrous oxide, I allow the coke to
dry; or I may soak the coke in a slurry of recently precipitated hydrated ferrous
or ferric oxide or of both or I may obtain the safe result in other ways; instead
of coating or impregnating coke in the manner before mentioned I may coat or
impregnate other substances.
sometimes divide the filter bed into two parts, the first containing Band and
gravel for straining the sewage or impure water and the second part containing
the oxidizing agent for oxidizing the sewage or impure water, the said oxidizing
agent being directly exposed to the air or having over it but a very thin coating of
Band. Instead of dividing the whole filtering area into a number of separate beds
I sometinies simply divide the beds at the top, that is to say the divisional walls
only penetrate the filtering material for a few inches.
In order to pass a current of air through the filter beds I connect the ventilating
pipes with ventilating cowls or with a fan or air blower or exhaust or with a chimney
or use other means.
The ventilating cowls before-mentioned consist of the well known large mouthed
pivoted cowls so arranged by means of a vane that the mouth of the cowl shall be
always exposed to the wind whereby the air from a large wind area can be con-
ducted down the ventilating pipes into the filter bed, this I term an injector cowl,

page_text: or instead of conducting the air into the bed by means of an injector cowl, I draw
the air out from the bed by means of exhaust cowls or ventilators, these I term
ejector cowls, I usually blow or conduct air in on one side of the filter bed and
draw or exhaust air out on the other side of the filter bed in order to obtain a
continuous current of fresh air through the bed.
Or I form a filter by placing in a chamber, tank or other receptacle of a suitable
shape a quantity of a suitable filtering or oxidizing agent, for instance hydrated
ferric oxide; obtained for example by decomposing a ferric salt with an alkali;
the liquid to be filtered which preferably has had all or most of the suspended
matter removed enters the tank at or near the bottom thereof and Hows upward
through the hydrated ferric oxide or other material at such a rate na to keep the
said hydrated ferric oxide or other material suspended in the liquid, and leaves the
tank or receptacle by an overflow at the top; the hydrated ferric oxide or other
material is prevented from escaping, if necessary by a mechanical strainer by
slowing the flow of the liquid at the top of the tank or receptacle or by other
means the entrance of the liquor to the tank may be capable of being closed and
a straining arrangement may be provided at the bottom; the liquid preferably
enters the tank or receptacle in such a way that it is evenly distributed over the
whole area; I may use any suitable filtering or oxidizing agent provided it can be
kept in suspension in the liquid, for instance hydrated oxide of manganese, finely
divided carbonised iron ore or any hydrated ferric oxide, and I sometimes blow or
force air through the liquid while being filtered.
The second part of my invention relates to improvements in the precipitation of
sewage or impure waters. I have found that better results are obtained if the
liquid to be precipitated enters the precipitation tank at or near the bottom thereof
insterd of at the top, more especially if the said liquid enters gently and without
any splash; I therefore allow the sewage to enter at the bottom of the precipitation
'tank. I sometimes employ deep tanks say twenty or thirty feet deep and allow
the sewage to enter at the bottom thereof or some few feet up from the bottom,
these tanks I do not construct of the same diameter or superficial area throughout
but bave the part for a short distance just above the inlet of the sewage.
smaller superficial area and may either have the remainder all of the same super-
ficial area or may enlarge it again preferably within a short distance of the top, or
1 may obtain similar results by making the tank, cone or pyramid shaped, the apex
being at the bottom; the part of the tank below the inlet of the sewage forms a
receptacle for the sludge whence it is drawn or pumped away.
of a
Or I lead the sewage or other liquid, after the addition of the precipitant when
one is used, from its level at the top of the precipitating tank down a pipe or
chamber, preferably vertical connected with the tauk at or near the bottom thereof,
and at the exit mouth of the said vertical pipe or chamber but inside the said pipe
or chamber, I fix a valve or its equivalent, this valve is opened and closed by a
rod to which is attached a float, the float being at or about the top of the vertical
pipe or chamber and being capable of adjustment on the rod attached to the valve,
so that it can be set in such a position that the vertical pipe or chamber is always
'full of the liquid when the tank is filling, no matter at what level the liquid may
be in the precipitation tank; the float automatically regulates the valve to
variations in the flow of the liquid; or I may let the liquid be conveyed to the
bottom of the tank down, a sloping pipe or carrier without a self regulating valve
attached thereto or I may obtain similar results in other ways.
Dated this Eleventh day of October 1892.

page_text: COMPLETE SPECIFICATION.
Improvements in the Filtration of Impure Waters and Sewage, and
in Apparatus and Arrangements and Materials for use therein,
and in Apparatus and Arrangements for use in the Precipitation
of Sewage.
I FRANK PULLEN CANDY of No. 56 Nightingale Lane Balham in the County
of Surrey 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:-
My invention consists first of the improvements hereinafter desoribed in the
purification of water and sewage by filtration and in apparatus and arrangements
therefor.
According to one of my said improvements I provide for the passage of air under
natural pressure through a portion or portions of a filter bed while the said bed is
in use by arranging in the said portion or portions ventilating. pipes open to the
atmosphere. In order that the air entering the said pipes may pass freely into the
portions of the filter bed in which they are situated it is necessary that the said
portions be composed of layers of the required material in. the form of pieces of
such size and shape that they will not lie compactly but in such a mannor that the
interstitial area of the said layers (which are hereinafter termed the aërating
layers) may be considerable. A suitable size for the pieces of filtering material in
the nerating layers is from a quarter of an inch to two inches in diameter but the
aërating layers should in all cases be composed of larger pieces of material than
those in any of the layers above them and the layer or layers of filtering inaterial
below the aërating layers should not be of smaller material than that in the finest
layers above them the object being to prevent the interstices between the pieces of
material in the aërating layers from being blocked or filled up by the water passing
through the filter bed. When the filtering materials in the several layers are of
the relative size hereinbefore indicated the water passing through the filters
merely trickles over the surfaces of the pieces of material of which the aërating
layers are composed and is thus thoroughly exposed to the action of the air
passing through the interstices of the said layers.
-
Where it is desirable to increase the velocity of the current of air passing
through the filter I provide either the inlet or the exit ends of the ventilating
pipes or both the inlet and exit ends with large mouthed pivotted cowls furnished
with vanes whereby the mouths of the cowls are caused to turn in the required
direction relatively to the wind. Or I connect the exit ends of the said pipes
with a chimney shaft.
Figures 1, 2, and 3 of the accompanying drawings illustrate methods of
constructing the filter beds and suitable arrangements of the ventilating pipes
therein Figure 1 being a vertical transverse section and Figure 2 a vertical
longitudinal section of a filter in which the aërating layer is of considerable.depth
say about one foot or more in dopth or thickness. Figure 3 is a vertical transverse
section of another filter in which the aërating layer is of less depth or thickness.
The same letters of reference indicate the said parts in all the said figures.
Referring to the said Figures 1, 2 and 3 a, a are the ordinary layers of fine sand
at the upper parts of the filters b is the aerating layer and c is the lowermost layer.
dd aro the walls of the filters ee are the inlet ventilating pipes and ff are the
outlet ventilating pipes 9 g are perforations formed in those parts of the anid pipes
which lie within the filter the object of which perforations is to provide for exit and
entrance of air to and from the filter. h is a pivotted cowl on the open end of the
inlet pipe shown in Figure 2 and i is the vaue by means of which the said cowl is
turned in the required direction by the action of the wind. Instead of mounting
pivotted cowls on the outer ends of the exit pipes any of the various forms of

page_text: cowls or appliances commonly used for preventing down draught or producing
updraught in chimneys and the ventilating pipes of buildings are suitable. Such
an appliance of known form is shown in Figure 2 on the end of the exit pipe fand
is marked i¹.
Each end of each ventilating pipe may be carried up above the level of the top of
the filter and be provided with a cowl or a number of ventilating pipes arranged in
the aerating layer may be connected to one main inlet or exit pipe or shaft
provided with a cowl. Or the cowls may be dispensed with the inlet and exit
pipes being merely open at their ends.
The diameter of the ventilating pipes may be about three inches and their
distance apart may be about three feet or more or less. The said pipes may be
arranged otherwise than as illustrated for instance the inlet ventilating pipes.may
be at the lower part and the exit pipes at the upper part of the aërating layer.
Instead of using continuous perforated pipes as illustrated in Figure 2 any
equivalent for such pipes may be used for instance ordinary land drain pipes laid
with open joints are suitable and instead of arranging pipes in the walls of
the filter for conveying air to the aërating layer shafts or passages communicating
with the pipes therein may be formed in the said walls which shafts or passages
may be merely open to the atmosphere at their upper ends or provided at the said
ends with cowls. Or those of the said shafts or passages through which air passes
from the filter may be connected to a chimney.
The material of which the aërating layers are composed may be of the kinds
ordinarily used in the construction of filter beds such for instance as gravel or pebbles
but I prefer to use for the said layers coke or other rough surfaced or porous
substance coated or impregnated with hydrated ferrons or ferric oxide or a
mixture of both by a known process which consists in soaking the coke or other
substance in a strong solution of ferrous or ferric sulphate or chloride or a mixture
of both and then allowing the coke or other substance to drain and afterwards
soaking it in an alkaline solution such as lime water whereby hydrated ferrous or
ferric oxide is precipitated in and upon the coke or other substance which hydrated
ferrous oxide may be oxidized by allowing it to dry.
Or I prepare a material for the aërating layers as follows. I take coke or
other substance having a rough surface and break it in pieces of the required size
and soak them in a thick slurry of freshly precipitated hydrated ferrous or ferric
oxide or a mixture of both and thereby coat the surfaces of the said coke or other
substance with the said hydrated iron oxide.
Two or more aërating layers may be formed in one filter bed.
In filters in which the oxidizing medium known in commerce as
"Polarite" or
other oxidizing medium is used I prefer to place an aërating layer immediately
above the layer of such oxidizing medium.
According to another of my said improvements I arrange for the use of
"Polarite or other oxidizing material in filters as hereinafter described.
"
Heretofore where oxidizing material has been used in filters layers of sand and
gravel have been placed above it for removing the coarser impurities from the
water entering the filter which layers of sand and gravel obstruct the passage of
air to the oxidizing material which is required to be acted on by air as freely as
possible when the filter bed is not in use. In order to obviate this objection I
divide the filter into two parts in one of which parts I form a bed of sand and gravel
and in the other a bed of the oxidizing material which oxidizing material being thus
directly exposed to or in contact with air rapidly absorbs oxygen when the filter
is at rest.
In using the said filters I pass the water first through the one formed of sand and
gravel and afterwards through the one formed oxidizing material.
Another of my said improvements consists in the method hereinafter described of
dividing a filtering area in which several filter beds are required to be formed.
Heretofore it has been customary to form the divisions by means of walls extending
from the bottom to the top of the filter. According to my said improvement I

page_text: form the said divisions at the upper part only of the filter by building dividing
walls or partitions on arches or on beams or girders carried by columns or on other
suitably arranged supports. The said dividing walls or partitions may be formed of
brickwork or wood or iron or other convenient and suitable material or materials.
Another of my said improvemente consists in the construction. of a filter as
hereinafter described and in the purification of water in the said filter as hereinafter
described.
The said filter consists of a tank or chamber of considerably greater sectional
aren at the upper part than at the lower part in which chamber is placed a quantity
of a purifying or oxidizing material in a state of fine division. Provision is made
for admission of the water to be purified at the lower part of the said tank or
chamber and for the exit of the purified water at the upper part thereof. Figure 4
of the accompanying drawings is a vertical transverse section of the filter and its
connections. is the tank or chamber, is a pipe or conduit by which the water to
be filtered is conveyed to the tank which pipe or conduit is furnished with a
valve ; m is a trough which surrounds the top of the tank and receives the
purified water passing from the filter. At the junction of the pipe or conduit k
with the tank is a grid n which is preferably hinged to the said tank. о ів я ріре
provided with a stop cock (not shown in the drawing) by means of which the tank j
may be emptied when necessary. In purifying water by use of the said apparatus
1 prefer to separate from the water by any suitable means any matter held
mechanically in suspension in it and place in the tank j a suitable purifying
material in the form of powder or in a state of fine division and admit the water to
the said tank in which the said water rises and mixes with the purifying material
which is kept in suspension in the entering water by the force of the upward flow
thereof. The rate of flow of the water into and through the tank is regulated by
the valve in such a manner that the motion of the water at and near the top of
the said tank shall not be sufficient to keep the purifying material in suspension
at the said part consequently the water overflows from the said tank and passes
into the trough m without carrying the said purifying material out of the tank.
From the trough in the purified water is conveyed away from the apparatus by
means of pipes or otherwise.
'
j
The tank may be circular or square or oblong or of any convenient form in plan.
Where it is of oblong form or of greater length than breadth I convey the water to it
by means of a conduit of such form that the said water passes from it at all parts
of the length of the said tank. Or I convey the water to the tank by means of a
series of pipes which open into the bottom of the tank at intervals.
In some cases I' arrange a trough or troughs within the upper part of the tank j
for receiving and conveying away the purified water which trough or troughs may
be supplementary to or in substitution for the trough m. I also in some cases
arrange a grid at or in the upper part of the tank j through which grid the purified.
water rises.
A suitable purifying agent for use in the said apparatus is hydrated ferrio oxide
which may be produced by decomposing a ferric salt with an alkali. Hydrated
manganic oxide and finely ground manganese dioxide and finely ground Polarite.are
also suitable purifying agents.
Where the purifying material used is hydrated forric oxide or the like and where
the action of the water entering the tank is not alone sufficient to separate the
particles of purifying material I prefer to arrange perforated pipes in or near the
bottom of the said tank and blow or force air through them among the particles of
purifying material either while the water is passing through the tank or after
temporarily shutting off the supply of water thereto. Or I agitate the purifying
material by other means such as by revolving blades or arms suitably mounted
within the tank.
My invention consists further of the improvements hereinafter described in
apparatus and arrangements for the purification of sewage by precipitation.
According to this part of my invention I form precipitation tanks and provide
•}

page_text: J
for inlet thereto of the sewage to be purified and for the exit of the effluent and
the exit or withdrawal of the precipitate or sludgo as hereinafter described with
reference to Figures 5, 6, 7 and 8 of the accompanying drawings.
P
Figure 5 represents in vertical section a precipitation tank and means for
supplying thereto the sewage to be treated and for withdrawing the sludge from
the said tank and for conducting the effluent therefrom. p is the tank g is a pipe
or conduit by which the sewage to be treated is conveyed to the tank and r is a
pipe or conduit through which the precipitate or sludge passes or is drawn from the
tank which pipes or conduits q r are furnished at any convenient part with valves
(not shown in the drawings) by means of which valves the passage of matters
through the said pipes or conduits may be controlled as required. s is a perforated
or unperforated plate or shield supported over the lower end of the pipe or.
conduit g the object of which plate or shield is to spread the stream of sewage
issuing from the said pipe or conduit. is a trough surrounding the upper edge of
the tank p into which trough the effluent passes. The said apparatus is used and
acts as follows;-The sewage to be treated admitted to the tank piby opening
the valve in the pipe or conduit g. The sludge or matter deposited or precipitated
from the sewage collects in the lower part of the said tank as the liquid rises
therein the rate of flow of the sewage through the pipe or conduit g being so
regulated by means of the valve therein that when the liquid in the tank has.
risen to the top thereof it is in a sufficiently pure state to be allowed to pass
therefrom by overflowing into the trough t. While the liquid is thus flowing into
the tank and the effluent is passing therefrom the sludge deposited in the tank is
allowed to pass from it through the pipe or conduit by opening the valve therein
to such an extent as will admit of exit of the said sludge at about the same rate as
it is deposited. When the addition of precipitants is required for the purification
of the sewage I prefer to add them to it before it passes the valve in the pipe or
conduit q. Instead of permitting the sludge deposited or precipitated in the tank
to pass continuously therefrom it may be removed intermittently. In all cases I
prefer to allow a considerable quantity of sludge to accumulate in the bottom of
the tank before opening the valve in the pipe or conduit r. Where it is not
convenient to allow the sludge to pass from the tank by gravity it may be removed
by pumping. The pipes or conduits y and r or either one or other of them may be
arranged inside the tank instead of outside. The modified arrangements of
troughs hereinbefore described with reference to Figure 4 for carrying off the
effluent from the filter illustrated in the said figure are applicable to the precipitation
tanks herein described.
Figure 6. of the accompanying drawings represents in vertical section a
precipitation tank and means for supplying thereto the matters to be trented therein
and for withdrawing therefrom the deposited or precipitated sludge. The action and
method of using the said tank and its appurtenances are the same as described with
reference to Figure 5 the only differences being in respect of the form of the tank
and the arrangement of the pipes or conduits by which the sewage to be treated is
admitted and the sludge discharged. The parts being marked with the same
letters of reference as those marked on the said Figure 6 further description is
unnecessary.
The object of constructing, sewage precipitating tanks as illustrated in Figures 5
and 6 of the accompanying drawings and passing the sewage into them at a part
where the sectional area is small compared with that at a higher part is to insure
the presence of a large quantity of coagulum above the inlet of the sewage which
coagulum acts as a strainer allowing the liquid portion of the incoming sewage
to pass through it to the upper part of the tank and retaining in the lower part
of the tank the coagulum contained in the said incoming sewage. It will therefore.
be understood that the position of the delivery end of the sewage inlet pipe q is a
point of considerable importance.
The tanks herein before described. with reference to Figures 5 and 6 may be
twenty or thirty feet deep and of any convenient area.

page_text: I bave found that it is advantageous to avoid as far as possible breaking up of the
congulum which is formed in sewage when a precipitant has been added thereto.
Therefore when I add precipitants to sewage before admitting it to precipitating
tanks of ordinary construction I prefer to provide for entry of the sewage at or
near the bottom of the tanks and in such a manner as to minimize splashing of the
sewage while it is entering.
In Figures 7 and 8 arrangements are illustrated for automatically admitting
sewage to precipitation tanks where the sewage to be treated is required to enter
the tanks at the lower part thereof and without avoidable splashing. Each of the
said figures illustrates in vertical section a portion of the precipitating tank which
is marked u and the connections between a reservoir of the sewage to be treated
and the said tank which connections in each case consist of a conduit va vertical
shaft and a passage y. In Figure 7 a sluice valve is mounted at the point of
junction between the shaft to and passage y which valve is raised and lowered
automatically by rise and fall of the liquid in the shaft to and conduit v through the
medium of a float z which is connected to the said valve by a rod z³ capable of
motion in a vertical direction in staples or sockets affixed to the wall of the
tank u.
I prefer to so connect the float to the rod as to admit of ready adjustment
of the distance of the said float from the valve and where the pressure of
the sewage against tho said valve is sufficient to cause excessive friction I arrange
wheels or rollers for the said valve to bear against. The slight leakage past the
valve consequent on this arrangement is of no importance. Where the weight of
the float is considerable arrange supports under it on which it rests when the
valve is closed. In Figure 8 a stop valve 2 is arranged at the point of junction of
the shaft w with the passage y which valve is worked by a float in the same
manner as the sluice valve. Any other convenient form of valve capable of
being actuated by a float may be used in substitution for those illustrated in
Figures 7 and 8. To prevent the sewage from rushing violently upward when the
valve is first opened 1 arrange a plate over the inlet passage y as shown at u'.
With the object of preventing splashing of the sewage I in some cases provide
for entry thereof into a precipitation tank as hereinafter described. I convey the
liquid to the tank by means of a pipe or conduit inclined at a slight angle for the
greater part of its length and turned upward about two feet from its end and
entering the tank at or near the bottom thereof. I find that an inclination of about
one in two is suitable.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I wish it to be understood
that I make no claim to the passing of air under artificial pressure into filter beds
and that I make no claim per se to the arrangement in filter beds of perforated
pipes for conveying air into such beds and that I make no claim to the preparation
of a material for use in filter beds by soaking coke or other porous substances in a
solution of a ferrous or ferric sulphate or chloride and afterwards decomposing
the said iron salt by means of an alkali. I also wish it to be understood that
make no general claim either to the filtration of a rising stream or body of water
or to precipitation tanks in which a continuous stream of the liquid under treatment
flows upward while the sludge or precipitate is or may be continuously withdrawn
or allowed to pass from the lower part but 1 declare that. I claim as my said
invention :-
First. The combination with a layer or layers of coarse filtering material in a
filter bed of ventilating pipes or conduits by which air under natural pressure is
conveyed to and from the said bed.
Secondly. The combination with pipes or conduits by which air under natural
pressure is conveyed to and from filter beds of cowls for increasing the velocity of
the air passing to and from the said beds.

page_text: Thirdly. The connection with a chimney of the exit ends of pipes or conduits
by which air is conveyed from the interior of a filter bed.
Fourthly. A filter composed in part of a layer or layers of porous material
treated or impregnated with iron oxide to which layer or layers a current of air is
supplied.
•
Fifthly. The preparation of a material for use as a filtering agent by soaking
coke or other substance having a rough surface in a thick slurry of freshly
precipitated hydrated iron oxide.
.
•
Sixthly. The filtration of water by causing it to flow upward through a vessel
or chamber containing a purifying agent in a sufficiently fine state of division to be
kept in suspension in the upwardly flowing stream of water substantially as
herein before described.
Seventhly. A filter bed the uppermost layer of which consists of an oxidizing
ugent.
Eighthly. The division of filter beds by means of walls or partitions extending
only a short distance beneath the surface thereof.
Niothly. The arrangement in a sewage precipitation tank having a smaller
sectional area below the upper. part than at the upper part of means for passing a
stream of sewage into the said tank within the part of smaller sectional area
substantially as and for the purpose hereinbefore:described.
Tenthly. A tank constructed as illustrated in Figure 5 of the accompanying
drawings, for use in the precipitation of sewage as hereinbefore described.
Eleventhly. A tank constructed as illustrated in Figure 6 of the accompanying
drawings, for use in the precipitation of sewage as hereinbefore described.
Twelfthly. Arrangements for admission of sewage to precipitation tanks at the
lower part thereof substantially as hereinbefore described with reference to
Figures 7 and 8.
Thirteenthly. The arrangement hereinbefore described for conducting sewage
into a precipitation tank which arrangement consists of an inclined pipe or conduit
communicating with the tank at or near the bottom thereof.
Dated the 12th day of August 1893.
F. PULLEN CANDY.