New or Improved Method in Sewage Precipitation.
Year: 1891

page_text: Date of Application, 24th Oct., 1891
Complete Specification Left. 25th July, 1892-Accepted, 3rd Sept., 1892
PROVISIONAL SPECIFICATION.
New or Improved Method in Sewage Precipitation.
I, GEORGE CARRINGTON PURVIS of 2 Argyle Place, Edinburgh in the County
of Midlothian, North Britain, Doctor of Medicine, do hereby declare the nature of
this invention to be as follows:-
This invention relates to a new or improved method in sewage precipitation.
The principle of the invention consists in passing sulphur dioxide (SO) and
carbon dioxide (CO), or one or other of these gases, into the sewage and precipi-
tating them, or one or other of them, as insoluble or almost insoluble salts or salt
by means of the basic or hydrated oxides of the alkaline earths in water, lime by
preference.
Dated this 23rd day of October 1891.
JOHNSONS,
115, St. Vincent Street, Glasgow, Petitioner's Agents.
COMPLETE SPECIFICATION.
New or Improved Method in Sewage Precipitation.
I. GEORGE CARRINGTON PURVIS of 43 Barclay Place, Edinburgh in the
County of Midlothian, North Britain, Doctor of Medicine, 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 a new or improved method in sewage precipitation.
The principle of the invention consists in passing sulphur dioxide (SO,) and
carbon dioxide (CO,), or one or other of these gases, into the sewage and precipi-
tating them; or one or other of them, as insoluble or almost insoluble salts or salt
by means of the basic or hydrated oxides of the alkaline earths in water, lime by
preference.
The gas or gases should be as thoroughly incorporated with the sewage as
possible by means of baffling plates so arranged that the stream of sewage is forced
to take a sinuous course, shortly before and immediately after it comes in contact
with the gas or gases, or the sewage may be made to descend towers (filled with
coke, brick or other suitable material) up which the gas or gases are made to
ascend thereby ensuring a proper mixing or solution of the gas or gases with the
sewage. After this the lime preferably in the form of milk of lime is added, to
this lime may be added (though it is not essential to do so) a small proportion of
some cheap soluble salt of alumina such as the sulphate of alumina, provided always
the lime added is in excess, i.e. after chemical action between the lime and
sulphate of alumina has taken place there is still a surplus or excess of lime as
nyurate.
e.g.
Per gallon of ordinary
neutral or faintly
alkaline sewage.
7.5 grains SO'
7.5 grains CaO (lime)
4.0 grains of ordinary sulphate of alumina
(Al, (SO) 3, 18, É₂O)
and it is this excess of lime (about 6.5 grains per gallon) which acts upon and
removes the gas or gases passed into the sewage.
To the lime, or lime and sulphate of alumina, may be added some of the cheap
soluble proto- or per-salts of iron such as the sulphate or chloride; also there may

page_text: be added charcoal (from 1 to 5 grains per gallon of sewage) in a fine state of division
or powder.
In all cases however, if the raw sewage be distinctly acid then the quantity of
lime must be over and above what is necessary to remove the free gas or gases
passed into the sewage, in order that the effluent from the sewage may be rendered
neutral or as nearly so as possible, any alkalinity due to the presence of free lime
(i.e. lime as hydrate) should in all cases be avoided.
Sulphurous acid may be cheaply and easily obtained by burning iron pyrites or
as a bye product in several metallurgical operations e.g. copper melting etc.
CO, (carbon dioxide) may be cheaply obtained by decomposing lime stone or
carbonate of lime by means of heat in the presence of air or steam or both.
And a mixture of SO, and CO, may be obtained by heating strong sulphuric
acid (H.SO) and coke or charcoal together.
The quantity of either gas employed may vary from 5 to 15 grains (somewhat
less of each gas if a mixture of sulphurous acid (SO2) and carbon dioxide (CO2) be
employed) per gallon of sewage of any water closeted town but if the sewage be
highly concentrated then more gas in proportion will be required. The quantity of
lime will depend mainly on the state of the raw sewage (whether acid or not) if acid
more lime than when the sewage is neutral or alkaline, the object being to obtain
neutrality as far as possible and at the same time to remove the free gas or gases
passed into the sewage.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
Passing sulphurous acid (SO,) and carbon dioxide (CO2) into the sewage (or one
or other of these gases) and removing the gas or gases by hydrate of lime either
alone or in combination with hydrate of alumina or hydrate of alumina and ferrous
or ferric hydrate obtained as already mentioned by the decomposition of the
respective salts by means of lime or milk of lime, provided always the lime hydrate
is in excess and is the remover of the gas or gases passed into the sewage, substan-
tially as hereinbefore described.
001
T
1000
JOHNSONS,
115, St. Vincent Street, Glasgow, Applicant's Agents.