An Improved Process for Purifying Waste Water or Sewage by Precipitation.
Year: 1898

page_text: Date of Application, 26th Nov., 1898
Complete Specification Left, 24th Aug., 1899-Accepted, 7th Oct., 1899
PROVISIONAL SPECIFICATION.
An Improved Process for Purifying Waste Water or Sewage
by Precipitation.
A communication by CARL GUSTAV GSELL, of 29, Luisenstrasse, Berlin, in the
Empire of Germany, Engineer.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street, Manchester, both
in the County of Lancaster, 118, New Street, Birmingham, in the County of
Warwick, and 8322, High Holborn, in the County of Middlesex, Civil Engineer,
do hereby declare the nature of this invention to be as follows:-
In purifying dirty or waste water or sewage by the precipitation of organic and
other impure constituents which are deleterious to health, out of said water,
sulphate of alumina and oxide of iron-or protoxide of iron sulphates are well
known as effective means for the precipitation.
These sulphates and their bases alumina and iron oxide or protoxide are
however too dear to permit of the precipitation of waste water on a large scale,
for instance for use with the sewage from town sewers.
This invention has for its object a process by means of which the purification
of sewage or dirty water by means of precipitation is considerably cheapened
and simplified and rendered universally applicable, and consists in the bases,
such as alumina, iron oxide and protoxide, which yield in combination with
sulphuric acid the effective precipitation substances and which are released at
each precipitation, being always again employed for producing the precipitate.
In the precipitation of sewage and waste waters by means of sulphate of
alumina and oxide and protoxide of iron sulphate the sulphuric acid contained
in these sulphates quits the bases and passes over into the ammonia and other
substances contained in the waste water, whilst the bases thereby released such
as alumina, iron oxide and protoxide are precipitated or deposited as mud in
combination with the other substances which have become free and insoluble
The present process consists in this mud obtained from a precipitation, which
mud containing the valuable bases alumina, iron oxide and protoxide, is utilized
as a precipitating material for further precipitations of dirty water or sewage
by adding to the same as much free sulphuric acid as converts the said bases
again into sulphates. In this manner a constant operation of precipitation of
sewage water on a large scale may be carried out in an extremely economical
manner, as after a quantity of sewage or dirty water has been purified by precipi-
tation the mud deposit obtained from the same is always treated with the
necessary quantity of sulphuric acid and is then conveyed into a further quantity
of the sewage or dirty water which is to be purified where it again effects a
precipitation.
The process may be carried out in various ways. The following appears the
most preferable:-
A quantity of sewage or waste water is conveved into a suitable tank and

page_text: precipitated by the addition of sulphate of alumina, sulphate of iron oxide and
protoxide of iron sulphate and then the clarified water is drawn off. As much
free sulphuric acid is added to the residual mud remaining in the tank as is
necessary for converting the bases contained in the mud into sulphates which
can easily be ascertained by means of reagents. The tank is then again filled
with sewage water and well stirred up after which immediately the precipitation
process takes place in the fresh lot of sewage water which is observable by the
formation of flakes which gradually sink whilst the liquid over them becomes
more and more clear and transparent. The clarified water is then as before drawn
off and the procedure is again repeated. The mud containing the bases may
however be added separately to the water which is to be purified and the same
applies to the sulphuric acid, without previously mixing the mud and the sul-
phuric acid. The sulphates which effect the precipitation are then only formed
in the sewage or dirty water itself and the action is quite the same.
The longer and more completely the liquid is each time allowed to settle, the
more completely will the bases necessary for effecting the next precipitation and
which have become free, be recovered in the deposit, and the more effective will
therefore be the action of the mud recovered on the next precipitation. For this
object it is advisable to allow the sewage or dirty water treated with the sulphate
mud to stand each time about three days exposed to the air. Even if in spite of
that, a small portion of the effective bases is drawn off with the clarified water
removed, this does not affect the continuous working, as waste water, more par-
ticularly in the case of sewage, itself contains alumina, iron oxide and protoxide
so that these bases are constantly replaced from the sewage water itself.
further separate addition of these bases can therefore hardly come into question.
On the other hand the amount of these bases contained in the mud rather
increases with each new precipitation.
A
The mud accumulated in the tank after a large number of precipitations which
has finally to be removed may be utilized by treating the same with sulphuric
acid, similarly to what was done before each separate precipitation, in order to
convert the bases into sulphates and then separating them from the mud by
extracting or washing out the sulphates formed. The mud may then be
employed for manure, for which object the bases withdrawn therefrom have little
value, whilst the lye or solution containing said bases is advantageously applicable
for initiating a further series of precipitations.
In case such a solution or lye is not at hand on starting the first operation the
necessary precipitating material for making the first precipitation may he
obtained from waste or sewage water which contains alumina, iron oxide and
protoxide itself so that it is not necessary to purchase these chemicals in order
to undertake the first precipitation and recovery of the first mud.
For this object the sewage water from the town sewers is treated with about 1%
of sulphuric acid and this mixture is allowed to stand in the open air for about
three to five days, by which means the said bases contained in the sewage are
completely converted into sulphate. About 10-20% of this sulphate liquid is
mixed with the waste water or sewage which is to be purified so that in the latter
the precipitation takes places in the manner herein before depicted, and the first
mud may be recovered therefrom which can then be employed for the next pre-
cipitation as herein before described. Any other substance containing alumina,
iron oxide and protoxide may however be employed for the first precipitation.
The necessary quantity of sulphuric acid which must be added before each
fresh precipitation of the mud amounts about to 1% whilst the necessary addition
of the sulphate mud to the water to be purified averages about 2%.
Dated this 25th day of November 1898

page_text: An P
OF BOage
by Precipitation.
A communication by CARL GUSTAV GSELL, of 29, Luisenstrasse, Berlin, in the
Empire of Germany, Engineer.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street, Manchester, both
in the County of Lancaster, 118, New Street, Birmingham, in the County of
Warwick, and 322, High Holborn, in the County of Middlesex, Civil 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 follow-
ing statement:--
For the purpose of purifying dirty or waste water or sewage by the precipi-
tation of organic and other impure substances contained therein and which are
deleterious to health, sulphate of alumina and oxide of iron or protoxide of iron
sulphates are well known as being effective means for such precipitation.
These sulphates and their bases alumina and iron oxide or protoxide are how-
ever too expensive to admit of their being used for the purification of waste
water on a large scale, such as would be required for instance in the case of
purifying the sewage from town sewers.
According to the present invention the bases alumina and iron oxide or pro-
toxide are obtained from the waste water itself, thus acquiring them in the
cheapest possible manner. The invention is based on the fact that the waste
water itself contains alumina and iron oxide or protoxide, and it consists in a
method of gaining these bases from the waste water, preparing the same into a
precipitating means and employing such medium obtained for the purification
of further quantities of waste water.
This method or process consists in that the mud obtained by precipitation from
a quantity of waste water or sewage and which mud contains the valuable bases
alumina, iron oxide and protoxide, is utilized as a precipitating material for
further precipitations of dirty water or sewage by previously treating and
manipulating the same with free sulphuric acid in such a manner as to convert
the said bases into sulphates. In this way a continuous operation of precipitation
of sewage or other waste water on a large scale may be carried out in an
extremely simple and economical manner.
Compared with other known methods of precipitation by means of lime, tar, .
chloride of magnesium, etcetera, the present process affords the great advantage
that in addition to saving the great expense of such other means of precipitation,
the mud obtained by the process according to this invention consists only and
exclusively of the substances contained in the sewage or waste water and which
substances are valuable for manuring purposes or as fuel, whereas the mud
obtained by other known methods of precipitation is intermixed with the ingre-
dients used for precipitating thus injuring or even wholly preventing its ultimate
profitable utilization.
In carrying out the process, the sewage or waste water to be purified, after
being conveyed into a suitable tank, has added to it the necessary quantity of
the prepared mud when the precipitation process is seen to be taking place almost
immediately by the formation of flakes which gradually sink to the bottom whilst
the liquid above becomes more and more clear and transparent. The clarified
water is then drawn off and the residual mud removed out of the tank to be

page_text: •
prepared in the manner hereinafter described, after which a further quantity of
sewage or waste water may be purified in the tank in the same manner.
If preferred the mud obtained need not be removed after each fresh precipi-
tation and after having drawn off the clarified water, but the same may con-
veniently be left at the bottom of the tank to be removed when a larger quantity
has accumulated. This manner of proceeding does not in any way interfere with
the effective working of the process, inasmuch as for every new precipitation
the prepared mud is added in proportion to the quantity of new waste water
conveyed into the tank to be purified.
In order to prepare the mud or precipitate into a precipitating means, as much
free sulphuric acid as is necessary to convert the bases contained in the mud
into sulphates is added to the same. The mixture will then preferably be piled
into heaps or brought into suitable utensils leaving the same in this state for a
period of say 3 to 5 days for the purpose of effecting the oxidation (crystalliza-
tion) of the mass, thereby promoting the chemical combination of the sulphuric
acid with the bases of the mud, thus completely forming the sulphates and con-
sequently rendering the means of precipitation most effective. At the same time
it may be stated that the said mixture of the mud and the sulphuric acid proves
to be possessed already of a certain degree of precipitating power shortly after
the said mixture has taken place and without having allowed the same to remain
to oxidize (crystallize) for a certain number of days.
A certain degree of purification of the sewage water may even be obtained by
adding, to the sewage, the mud containing the bases and the sulphuric acid each
separately and without mixing the same previous to their addition, or without
any previous oxidation or crystallization of such mixture, but, as will be easily
understood, the effect of each treatment must necessarily leave a good deal to be
desired.
The mud accumulated after a large number of precipitations which has finally
to be removed may be utilized by treating the same with sulphuric acid, similarly
to what was done before each separate precipitation, in order to convert the
bases into sulphates and then separating the sulphates formed from the mud by
extracting or washing them out. The mud may then be used as manure, for which
object the bases withdrawn therefrom have little value, whilst the lye or solution
containing the said bases may with advantage be used for initiating a further
series of precipitations. In a dried state the mud may also serve as fuel.
In case such a solution or lye as just mentioned is not at hand on starting the
first operation, the necessary precipitating material for making the first precipi-
tation may be obtained from waste or sewage water which contains alumina, iron
oxide and protoxide itself so that it is not necessary to purchase these chemicals
in order to undertake the first precipitation and recovery of the first mud.
For this object the sewage water from the town sewers is treated with about
1% sulphuric acid and this mixture is allowed to stand for from three to five
days, by which means the said bases contained in the sewage are completely con-
verted into sulphates. The sulphate liquid thus obtained is to be used for pre-
cipitating a further quantity of waste water or sewage in the manner hereinbefore
described, and the sediment recovered thereby may be employed for the next
precipitation as previously described. Any other substance containing sulphate
of alumina, iron oxide or protoxide may however be employed for the first pre-
cipitation.
The sulphate mud will be equally effective as a precipitating means both in a
humid and in a dry state.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed as communicated to
me by my foreign correspondent, I declare that what I claim is :-
The process for purifying waste water or sewage by precipitation, consisting
in adding to the mud obtained by a preceding precipitation of waste water, as

page_text: much sulphuric acid as is required to convert the bases contained in the mud
(alumina, iron oxide, iron protoxide) into sulphates, and precipitating with this
product a fresh quantity of waste water, the first precipitation for obtaining the
first mud being effected in any convenient manner, substantially as described.
Dated this 23rd day of August 1899.
WM. P. THOMPSON & Co.,
Agents.