Treating or Purifying Sewage, Waste Liquors from Manufactories, and other Foul Liquids, and Producing Valuable Substances therefrom.
Year: 1887

page_text: Date of Application, 19th Apr., 1887
Complete Left, 19th Jan., 1888
Complete Accepted, 24th Feb., 1888
Treating or Purifying Sewage, Waste Liquors from Manufactories,
and other Foul Liquids, and Producing Valuable Substances
therefrom.
We GEORGE EDWARD DAVIS of 301 Great Clowes Street, Manchester in the
County of Lancaster, Chemical Engineer and JAMES BENNETT AITKEN of Widnes
in the County of Lancaster chemical manufacturer do hereby declare the nature of
this invention to be as follows:-
In most if not all of the processes at present practised for the purification of sewage
and other foul liquids, the resultant sludge is but of small value owing to the paucity
of those fertilizing matters which give to a manure its real value, such as phosphate,
of lime.
In working our invention we add to the raw sewage a certain known quantity of
tribasic phosphate of soda, and if there is not present a sufficient quantity of soluble
lime salts we add an equivalent proportion of a soluble lime salt also. Chloride of
calcium which is a waste product in many processes is found to be a useful forn of
lime salt, sulphate of lime is also useful, or a solution of ordinary bleaching powder
may be successfully employed.
The quantity of tribasic phosphate of soda necessary for the purification of sewage
or other foul liquids, must necessarily vary according to the nature of the sewage or
other foul liquids to be treated, but generally it may be stated that ten pounds of the
tribasic phosphate of soda will be found sufficient for one million gallons of the
sewage.
The addition of the tribasic phosphate of soda and of the lime salt to the sewage
causes a sludge or fine mud to be precipitated, which is to be collected and dried in
any known manner, when it is ready for sale as a precipitated phosphate of lime of
high value.
The semi-dry sludge may also he converted into a high class manure by treating it
in the moist state with oil of vitriol, stronger than that which is usually employed in
making artificial manures. In order to effect this, the semi-dry sludge is placed in a

page_text: pug-mill, kneader, or any form of manure mixer and thoroughly mixed with the oil
of vitriol. By this means a dry friable superphosphate of lime is produced without
the employment of any artificial heat for drying.
The exact quantity of oil of vitriol required, and its specific gravity must be calculated
after knowing the composition of the semi-dry sludge, which is very variable, but it
may be taken as a guide, that twenty hundredweights of sludge testing thirty-six per
cent. of phosphate of lime will require six hundredweights of oil of vitrol of a specific
gravity of 1750. In some varieties of sludge there exists a large quantity of carbonate
of lime also. This also consunies oil of vitriol in the proportion of thirty hundred-
weights of oil of vitriol of 1600 specific gravity to every ton of carbonate of lime
present.
In other varieties of sludge, it is necessary in order to improve the quality of the
manure to partially remove the carbonate of lime. This may be done by treating the
sludge with dilute hydrochloric acid in the proportion of five parts of muriatic acid
of 1050 specific gravity to each part of carbonate of lime found in the sludge by
analysis. The chloride of calcium formed by this operation may be used again in the
early portion of the process.
Should any phosphate be retained in solution in the sewage effluent, or in the
effluent from other foul liquids such effluents may be further treated with a solution
of alumina, a solution of iron or a solution of manganese, either separately or combined
in order to further purify such liquids.

page_text: COMPLETE SPECIFICATION.
Treating or Purifying Sewage, Waste Liquors from Manufactories,
and other Foul Liquids, and Producing Valuable Substances
therefrom.
We, GEORGE EDWARD DAVIS of 301 Great Clowes Street Manchester in the
County of Lancaster Chemical Engineer and Consulting Chemist, and JAMES
BENNETT AITKEN of Widnes in the County of Lancaster, Chemical Manufacturer
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:
In most if not all of the processes at present practised for the purification of sewage
and other foul liquids, the resultant sludge is of but small value owing to the paucity
of those fertilizing matters such as phosphate of lime which give to a manure its
real value.
In working our Invention we add to the raw sewage or other foul liquid a certain
quantity of tribasic phosphate of soda, preferably in the state of solution and if there
are not enough lime salts present to combine with the phosphoric acid contained in
this given quantity of tribasic phosphate of soda we add an equivalent of a lime salt
also. Chloride of Calcium which is a waste product in many factories, is a useful
form of lime salt, or a solution of bleaching powder may be likewise usefully
employed, or a sulphate of lime.
The quantity of tribasic phosphate of soda to be used, necessarily varies according
to the nature of the sewage or other liquid treated, but generally about ten pounds
will be sufficient to treat one million gallons of the sewage though we have seen some
qualities of sewage and other foul liquids which have required one hundred pounds of
tribasic phosphate of soda to carry out the operation successfully, per million gallons
treated.
The addition of the phosphate and of the lime salt as hereinbefore described will
cause a sludge to be precipitated. This sludge must be collected and dried in any
known manner when it is ready for sale as a precipitated phosphate of high value.
The semi-dry sludge may be also converted into a high class manure by treating it
in the moist state with oil of vitriol, stronger than that usually employed in making
artificial manures.
In order to effect this the semi-dry sludge is placed in a pug-mill, kneader, or
manure mixer and treated with the oil of vitriol. By this means a dry friable super-
phosphate is produced without the employment of any artificial heat for drying. The
exact quantity of oil of vitriol required, and its strength must be calculated after
ascertaining the exact chemical composition of the semi-dry sludge, but it may be
taken as a guide that every three tons of tribasic phosphate of lime present in the
sludge requires two tons of oil of vitriol of 166° Tw. and the vitriol should be of such
a strength that the resulting manure contains about 15 to 20 per centum of hygroscopic
water.

page_text: In some varieties of sludge there exists a large quantity of carbonate of lime. This
also consumes oil of vitriol-one ton of the dry carbonate of lime requiring one ton
of oil of vitriol of 166° Tw., but it is better to treat the sludge with dilute hydrochloric
acid, by well known means so as to eliminate the carbonate of lime or nearly so, before
treating the sludge with the oil of vitriol.
.
When it is desired to remove the carbonate of lime by means of hydrochloric acid,
the said acid must be used in the proportion of about five parts of hydrochloric acid
of specific gravity 1050 to each part of carbonate of lime found in the sludge by
analysis. It is not advisable to abstract the whole of the carbonate of lime, as in this
case there would be a danger of loss of phosphate of lime. The sewage or other foul
liquid after the sludge has settled from it is now clear and bright and very unlike the
original fluid.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed, we declare that what
we claim is :
The use of tribasic phosphate of soda for the purpose of treating or purifying
sewage, waste liquors from manufactories and other foul liquids and so producing
valuable substances therefrom substantially as is herein described; and
Secondly, the use of tribasic phosphate of soda, combined or used in conjunction
with soluble salts of lime, for the purposes beforementioned and in the manner
hereinbefore described.
1000