Improvements in the Filtration of Sewage or Impure Waters.
Year: 1898

page_text: Date of Application, 7th May, 1898
Complete Cossification | ott 7th Feb 1899-Accepted. 18th Mar., 1899
Complete
Date of Application, 7th May, 1898
fication / oft 7th Feb 1899-Accented. 18th Mar., 1899
PROVISIONAL SPECIFICATION.
Improvements in the Filtration of Sewage or Impure Waters.
I, JAMES YATE JOHNSON, of 115, St. Vincent Street, Glasgow, Chartered Patent
Agent (being a communication from abroad by George Carrington Purvis, M.D.,
Bacteriological Institute, Grahamstown, Cape Colony), do hereby declare the
nature of this invention to be as follows;-
or
The principle of this invention which relates to improvements in the filtration
of sewage or impure waters consists in causing the sewage or impure water (freed
from suspended matter as far as possible by straining or by precipitation or by
both methods combined) to flow through a bed or mass of porous material
materials such as sand, gravel, coke, burnt clay, or any other suitable substance,
the porous material or materials being laid between beds of non-porous material
or enclosed in one or more non-porous tubes of any suitable shape, which beds,
tube, or tubes are so inclined to the horizon as to enable the sewage or impure
water to flow slowly through the filtering medium and thus enable the micro-
organisms living in the porous material and sewage to bring about a considerable
purification of the latter.
When the filter beds, tube, or tubes are of such great length that any portion
or portions of the filtering medium is likely to be insufficiently aerated, then such
portions can be aerated by means of shafts or tubes leading from the filtering
medium below to the external air above, the shafts or tubes being filled, if neces-
Or if the nature of the ground permit
sary, with lightly packed porous material.
of it the aeration may be effected by dividing the filter bed, tube, or tubes, into a
series of sections, with a short fall and exposure of the sewage to the external
air. The filter beds are worked on the intermittent system.
Improvements in the Filtration of Sewage or Impure Waters.
I, JAMES YATE JOHNSON, of 115, St. Vincent Street, Glasgow, Chartered Patent
Agent (being a communication from abroad by George Carrington Purvis, M.D.,
Bacteriological Institute, Grahamstown, Cape Colony), 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 to improvements in the filtration of sewage or impure
n
.
077

page_text: waters and consists in causing the sewage or impure water (freed from suspended
matter as far as possible by straining or by precipitation or by both methods
combined) to flow through a bed or mass of porous material or materials such
as sand, gravel, coke, burnt clay, or any other suitable substance, the porous
material or materials being laid between beds of non-porous material or enclosed
in one or more non-porous tubes or drains of any suitable shape, which beds,
tube, or tubes are so inclined to the horizon as to enable the sewage or impure
water to flow slowly through the filtering medium and thus enable the micro-
organisms living in the porous material and sewage to bring about a considerable
purification of the latter.
As an example of carrying out iny invention I will proceed to deseribe the same
with reference to the accompanying drawing which represents a section of the
filter bed.
The sewage may with advantage be first strained through a screen to intercept
the grosser particles and be, secondly, subjected to some kind of precipitation such
as by means of lime or other suitable substance or substances. About 3 to 4
grains of lime per gallon of ordinary (non-acid) sewage will in general be found
sufficient but if the sewage be distinctly acid a much larger amount of lime will
be necessary.
The filter bed consists of a bowl or tank portion A the continuation B of which
is arranged below the ground and-formed of some material which is impervious
to water, such as cement. The sewage enters the said tank by the sewer pipe B¹.
The filter bed may be of any shape, such as rectangular, oval, elliptical, circular or
other similar section, the portion B of the bed being more or less straight or
curved, or inclined at various angles at different parts of its course; or it may be
spirally coiled when the space is limited provided that there is always sufficient
"head" to cause a slow and gentle flow of the sewage towards its outlet C, which
may discharge into a stream, canal, the sea or other convenient waterway or
place.
The tank and channel, or continued portion, of the filter bed are both loosely
packed with some filtering substance, or substances such as gravel, pea-ballast,
coke-breeze, sand or the like and in order that the latter portion of the bed
may be sufficiently aerated it may be interrupted at short intervals by the air
shafts or tubes D leading from the filtering material below to the external air
above.
For convenience the filter bed may be said to be made up of sections, thus
section 1 extends from and including the tank A to the first air shaft D but not
including the latter. Section 2 extends from and including the first air shaft D
to the second air shaft D but not including the latter and so on for the remaining
sections which may be of any number, though only four are shewn in the drawings.
If a single material such as coke-breeze or pea-ballast (which are well known
filtering agents) is to be employed then the whole tank and channel portion may
be filled with such substances, care being taken to prevent the coke from floating
by a layer or two of coarse gravel placed on the top of the coke-breeze. But
if it be necessary to use two or more filtering substances then as a general rule
the coarser material, such as coarse gravel, should occupy the first or proximal
part of each section of the filter and the finer, such as pea ballast or small coke
(free from dust) the distal part of each section with a general tendency of the
finest filtering material such as sand to occupy the furthest end of the filter, i.e.
towards the outlet. Thus the first parts of each section are filled with coarse
materials but it is preferable that the first part of the first section be occupied by
coarser material than the first part of the second section and the first part of the
second section with coarser material than the first part of the third
section, that is to say corresponding parts of successive sections are occupied
by finer and finer filtering materials till eventually the distal or outlet end may
come to be occupied by fine sand. With this latter material care is necessary to
prevent it being washed away and also to prevent it remaining clogged or wet with

page_text: water during the intervals of rest, say from 4 to 8 hours daily, which the filter
should have. This may be effected by slightly tilting up the outlet end of the
filter and by having only a thin extent of sand.
The air shafts I may rise slightly above the level of the ground surface to
prevent rainwater from entering them and may be protected by gratings in any
convenient way.
It is not necessary that the air shafts be packed with filtering material but if
packed, some coarse filtering material must be employed as fine material is apt to
impede the aeration of the filter bed.
Or if the nature of the ground permit of it the aeration may be effected by
dividing the filter bed tube, or tubes, into a series of sections, with a short fall
and exposure of the sewage to the external air.
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;
-
In the filtration of sewage or impure water, the employment of a filter bed,
more or less underground, composed of a channel or channels B containing filtering
materials, Lue said channel or channels leading from the tank A and being pro-
vided with air shafts ]), all constructed and arranged substantially in the manner
as hereinbefore described and shewn in the accompanying drawings.
Dated GIS On day or rebruary 1099.
JOHNSONS.
Applicant's Agents,
115, St. Vincent Street, Glasgow.