AN IMPROVED PROCess and apparatUS FOR PURIFYING OR DISINFECTING SEWAGE
Year: 1882

page_text: LETTERS PATENT to Friedrich Petri, Doctor of Philosophy of Berlin, German
Empire for an Invention of "AN IMPROVED PROCess and apparatUS FOR
PURIFYING OR DISINFECTING SEWAGE"
€
PROVISIONAL SPECIFICATION left by the said Friedrich Petri at the Office
of the Commissioners of Patents on the 6th November 1882.
FRIEDRICH PETRI, Doctor of Philosophy, of Berlin, German Empire "AN
IMPROVED PROCESS AND APPARATUS FOR PURIFYING OR DISINFECTING SEWAGE
"
This invention relates to improvements in the process for the purification of sewage
described in the Specification of foriner Letters Patent No. 5390 December 9th 1881,
and in apparatus therefor.
According to the present invention I provide a double filter in order to permit
one of the said filters to be emptied without interrupting the process.
From the main inlet pipe the sewage enters the channels in communication with
the purifying basins. These channels can be opened or closed by means of sluice-
valves, according as it is desired to let the sewage flow into the one or other system
of basins.
From one of these channels the sewage enters the first purifying basin which is
in two parts. The one part is separated from the other part by a division
composed of masonry provided with holes, or of wood, or iron giating. In the first
of the two divisions tho dense parts and conrser admixtures of the sewage
accumulate, whilst the liquid parts pass through the grating into the other division
and there undergo the first mechanical, and partly chemical purification. This
arrangement of a mechanical cleanser in the shape of a wall or grating presents a
considerable advantage over the old process by which the coarser admixtures very
quickly reduced the perviousness of the peat.
The absorbing filling of the second division or filtering bed consists as is described
in the Specification herein before referred to, of pervious vegetable material such as
peat, charcoal, or the like. By means of this vegetable material, ammonia and
dissolved organic substances which are capable of becoming foul, are largely
atsorbed and in consequence of the antiseptic properties of the peat, are prevented

page_text: from becoming decomposed. The exhalations of this filtering bed which in the
same way as in irrigation fields, become highly objectionable to the neighbourhood,
can be efficaciously prevented by means of disinfecting and gas absorbing covers.
For this purpose a cover of peat impregnated with carbolic acid and bi-sulphate of
potash, or preferably superphosphate, may be used. In order to protect the said
covering from being wetted by the foul matter beneath, it is advisable to arrange
the same on wooden hurdles or thin gratings placed at such a height over the
material being filtered that it is impossible to wet them.
To facilitate the application and removal of the said covers they may be made
in parts or sections of suitable size, and provided with handles so that they may be
easily lifted. By means of this arrangeinent it is possible at any time to ascertain
the condition of the absorbing material and the amount of deposit of consistent
matter in the different divisions.
The sewage water after having undergone a partly mechanical and chemical
purification in the filtering basins passes thence through a sieve into a channel
extending throughout the whole length of the basin and is thereby separated from
the absorbing material. As the sieves extend throughout the whole length of the
basin, the water can freely enter the said channel, a stoppage being thereby avoided
in the basin and the inlet channels At the end of this channel into which the
partially purified water flows, organic chlorides are introduced into the water in
order to prevent the development of fetid fermentations.
The said channel is connected with a zig-zag shaped channel which emerges into.
a wide cleaning basin
Small quantities of sulphate of alumina in the proportion of about 5 parts
to 100,000 parts, and lime milk (varying according to the kind of sewage) are now
added. The introduction of these chemical agents takes place before the sewage
enters the zig-zag channel, and in such a manner that after the chlorides have been
added the sulphate of alumina flows in, and then the lime water. To weaken the
working of the sulphate of alumina upon the sewage water and to prevent the
escape of noxious properties another filter layer of raw lime stone mixed with peat
is used; the purification takes place as follows, Near the entrance of the zig-zag
channel is placed a tank from which drop organic raw chlorides derived from
chloride of lime raw hydrochloric acid, and raw spirit strongly diluted Behind
this is placed another tank for the solution of sulphate of alumina. The quantity
of the latter solution has to be regulated according to the degree of purity of the
sewage that passes through the pent filter. The said solution occasions under any
circumstances a precipitation of organic matters such as alumina precipitates which
hold the ammonia very strongly, and in which, at the same time, organic matters
of variable nature are combined. The sulphuric acid of the sulphate of alumina
will form gypsum with the lime of the sewage water, and this gypsum formation
is, through the further addition of lime milk, much increased.
Near one of the bends of the zig-zag channel is placed a receiver or tank which is
filled with slacked lime. On the bottom of this receiver is a cock. Through
this cock lime milk (the quantity of which can be regulated) drops into the
sewage water.
Above the aforesaid receiver is arranged a larger holder also provided with a cock
through which water flows upon the lime lying in the lower tank, and thus, by
means of the two cocks the formation of lime milk can be regulated as required.
The quantity of lime to be added must be regulated according to the quantity of
the previously named purifying materials used. But in any case it must be so
regulated that the water as it leaves the zig-zag channel after it has been chemically
treated, and which will then appear slightly muddy through alumina and lime
precipitations, should shew a slight alkaline reaction. In order to mix the different
ingredients and especially the lime milk thoroughly with the sewage by which the
effect of the latter is very much improved, it is advisable to let n paddle or brush
wheel rotate in the zig-zag channel. A small motor for this purpose can be driven
by the flowing sewage water or by other suitable means.

page_text: The water slightly alkaline through the free lime then enters the clearing basin.
In this basin the water coming out of the zig-zag canal at once assumes a relatively
small velocity, so that the duration of the time of action of the air upon the water is
thereby materially increased and the surplus of lime is neutralized through the
carbonic acid of the air and precipitated as carbonate of lime and alumina. In
order to aid this precipitation on the floor of the basin, the said floor is made to slopo
upwards towards the back of the basin. Thereby the precipitated chalk is prevented
from being carried by the stream in large quantities to that part of the basin.
In the said back part of the cleaning basin, a filter is arranged which consists
of peat-rubbish or other suitable material, mixed with coarse limestone rubbish.
The important effect of the limestone is to keep back small quantities of sulphate
of alumina, which may possibly not have been absorbed entirely in the former
process. Thus gypsum will be produced in the peat mass from the limestone, and
alumina will be deposited on the peat, which alumina itself is a most activo
purifying filter material. This second peat and limestone filtration produces a
valuable manure, inasmuch as peat with gypsum (which mixture is produced in the
process of purification) particularly if impregnated with alcaline earth will acquire
a high agricultural importance. The water thus subjected to an after filtration and
which will now contain only small quantities of the chemicals with which it has
been treated, reaches an outlet. The said outlet is connected with a basin in which
a gravel bed is arranged; as the sewage thus mechanically and chemically purified
as hereinbefore described flows through this gravel bed it is thoroughly purified
and emerges therefrom quite clear and free from all noxious admixtures, so that it
may be led anywhere without causing any damage to animal or vegetable life.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the 'said Friedrich Petri in the Great Seal Patent Office on the 3rd May
1883.
FRIEDRICH PETRI, Doctor of Philosophy of Berlin, German Empire.
IMPROVED PROCESS AND APPARATUS FOR PURIFYING OR DISINFECTING SEWAGE
"AN
"
This invention relates to improvements in the process of purifying sewage
described in the specification of former Letters Patent dated December 9th 1881
No 5390 and to apparatus therefor.
In the accompanying drawing
Figure 1 is a plan of a double filter constructed according to this invention.
Figure 2 is a longitudinal section of the same on the line w w Figure 1
Figure 3 is a section on the line xx Figure 1, and
Figure 4 is a section on the line yy Figure 1.
According to the said invention I provide a double filter as shown in Figure 1, in
order to permit one of the said filters to be cleansed without interrupting the process.
From the main inlet pipe A, Figure 1, the sewage enters the channels A' A¹
communicating with the purifying basins. These channels can be opened or closed
by means of the sluice valve A, according as it is desired to let the sewage flow into
the one or other system of basins.
From one of the channels A¹ the sewage enters the first purifying basin B B',
which is divided into two parts. The part B is separated from the part B' by a
partition B composed of masonry provided with holes, or of wood or iron grating.
In the first of the two divisions the dense parts and coarser admixtures of the
sewage accumulate, whilst the liquid parts pass through the grating B2 into the
division B' and there undergo the first imechanical, and partly chemical purification.
This arrangement of a mechanical cleanser in the shape of a wall or grating presents
a considerable advantage over the old process, by which the coarser admixtures
very quickly reduced the perviousness of the peat which was employed.
The absorbing filling of the division or filtering bed B' consists, as is described in
the said former specification of pervious vegetable material; such as peat, charcoal
or the like. By means of this vegetable cellular material, ammonia and dissolved
organic substances, which are capable of becoming foul, are largely absorbed, and
in consequence of the antiseptic properties of the peat, are prevented from becoming
decomposed.
The exhalations of this filter bed, which in the same way as on irrigation fields,
can become highly objectionable to the neighbourhood, can be efficaciously prevented
by means of disinfecting and gas-absorbing covers. For this purpose a cover of
peat impregnated with carbolic acid and bi-sulphate of potash, or preferably super
phosphate may be used. The said covers also serve the purpose of protecting the
filters from severe cold. In order to protect the said covering from being wetted
by the foul matter beneath, it is advisable to arrange the same on wooden hurdles
or thin gratings placed at such a height over the material being filtered that it is
impossible to wet them.
To facilitate the application and removal of the said covers they may be made in
parts or sections B' of a suitable size, and provided with handles, so that they may
be easily lifted. By means of this arrangement it is possible at any time conveniently
to inspect and ascertain the condition of the absorbing material in the part B', and
the amount of consistent matter deposited in the different portions thereof without
loss of time
The sewage water after having undergone a partly mechanical and chemical
purification in the filtering basin BB', passes thence through the sieve or strainer B³
Figures 1 and 2, into the channel C (which extends throughout the whole length
of the basin,) and is thereby separated from the absorbing material. As the sieves
extend throughout the whole length of the basins, the water can freely enter the

page_text: Satu chamel, a stoppage being thereby avolaca in the Dasın and the met
channels A A'.
At the end of this channel C into which the partially purified water flows
organic chlorides are introduced, in order to prevent the development of fetid
fermentations.
The channel C is connected with a zig-zag shaped channel D' to D³ which
emerges into a wide basin G
"
Before the sewage enters the channel D' D³ to D³ small quantities of sulphate of
alumina in the proportion of about fivo (5) parts to one hundred thousand (100,000)
parts of sewage water, and lime milk (tho quantity of which varies according to the
character of the sewage under treatment) are added. The introduction of these
chomical agents takes place after the chlorides have been added the sulphate of
alumina flowing in first and then the lime water. To weaken the action of the
sulphate of alumina upon the sewage water, and to prevent the escape of
noxious properties, another filter-bed of raw limestone mixed with peat is used,
The manner of carrying out this part of the process is as follows:-that is to say.
Near the entrance to the channel D is placed a tank E from which drop organic
raw-chlorides, derived from chloride of lime, raw hydrochloric acid, and raw spirit
in strong solution. Against tho tank E is placed another tank E' containing the
solution of sulphate of alumina. The quantity of the latter solution added is
regulated according to the degree of purity of the sewage that passes through the
peat filter. The said solution occasions the precipitation of organic matters, by
forming alumina and the like which hold ammonia very strongly and in which, at
the same time, organic matters of variable nature are combined. The sulphuric acid
of the sulphate of alumina, will form gypsum with the lime of the sewage water,
and this gypsum formation is then through the further addition of lime milk, much
increased. The lime milk is introduced in the following manner, that is to say :-
Near one of the bends of the zig-zag channel is placed a receiver or tank E",
which is filled with slacked lime. At the bottom of this tank is a cock e through
which lime milk (the quantity of which can be regulated) drops into the sewage
water, In order to produce the said lime milk I arrange above the aforesaid receiver Ell
a larger holder F, (Figures 1 and 2) provided with a cock f; through which water
flows on to the lime in the tank E". By means of the two cocks e and f the formation
of lime milk can be regulated as required.
The quantity of lime that is added must be regulated according to the quantity
of the previously named purifying materials used. But in any case it must be so
regulated, that the water, as it leaves the zig-zag channel D¹ to D³, after it has been
chemically treated, and which will then appear slightly muddy through alumina
and lime precipitations, should show a slight alkaline reaction
In order to mix the different purifying agents, and especially the lime milk,
intimately with the sewage water, the action of the said lime water being much
improved thereby, it is advisable to arrange a paddle or brush wheel to rotate in
the zig-zag channel D¹ to D³. A small motor for driving the said wheel can be
driven by the inflowing unpurified sewage water or by other suitable means.
The water slightly alkaline through the action of the free lime now enters the
basin G. The action of the lime upon the sewage can be neutralized for example
with "curcuma" and by inspecting the sewage as it leaves the peat filter the
quantity of lime required to be added can be ascertained. In the basin G the
liquid issuing from the channel D' to D' at once assumes a relatively small velocity,
so that the length of time during which the air acts upon the water is materially
increased, and the surplus of lime is neutralized by the carbonic acid of the air, and
precipitated as carbonate of lime together with the argillaceous earth on the floor
of the basin.
In order to aid this deposition on the floor of the basin G the said floor is
inclined upwardly towards the part G', whereby the precipitated chalk is
prevented from being carried by the stream in large quantities to that part of the
basin.

page_text: In the part G' of the basin G a bed of filtering material is placed which consists of
peat rubbish or other suitable vegetable substance mixed with coarse limestone
rubbish. The object of the limestone is to decompose small quantities of sulphate of
alumina, which may possibly not have been absorbed in the former part of the
process. Thus gypsum will be produced in the peat mass from the limestone, and
instead thereof alumina will be deposited in the peat, which alumina itself is a most
active purifying filtering material. This second peat and limestone filtration
produces a valuable manure in as much as peat and gypsum which mixture is
formed during the process of purification (at times impregnated with alkaline
earth) acquires a high agricultural importance.
The water thus subjected to an after filtration, and which will now contain only
small quantities of sulphate of lime now reaches an outlet H.
The said outlet is connected with a basin I, in which is a gravel filter bed; as
the sewage water mechanically and chemically purified as herein before described
flows through this gravel bed it is thoroughly purified and emerges therefrom
_through the outlet K quite clear and free from all noxious admixtures, so that it
may be led anywhere without causing any damage to animal or vegetable life.
Having thus fully described my said invention and the manner of performing
the same I wish it understood that I claim
First. In the process of purifying sewage, subjecting the same to a double
filtration through a vegetable cellular material and to a chemical treatment
(between the stages of the filtration) by the successive application of the raw
cblorides, raw sulphate of alumina, and lime milk, substantially as, and for the
purpose, specified.
Second. In a peat filter, the employment of a cover constructed substantially as
described, for the purposes-specified.
Third. In the above described apparatus for the purification of sewage, the
employment of a rotating brush or paddle wheel, substantially as, and for the
purpose, specified.
Fourth. The filter bed consisting of peat rubbish and coarse limestone, for decom-
posing and removing the surplus alumina, substantially as, and for the purpose,
specified.
Fifth. In combination with peat filters and channels for the chemical treat-
ment of sewage liquid, the employment of flat clarifying basins in which the
separation from the said liquid of the surplus lime takes place through the action of
the carbonic acid in the air.
Sixth. In combination with the peat filters and means for chemically treating
sewage liquid, the employment of a gravel filter for finally purifying the said liquid,
substantially as above set forth.
Seventh. In the apparatus for carrying out the process herein before described,
the double arrangement of filters, consisting mainly of the channels A, A' which can
be opened or closed by means of the sluice valves A2, A3, the basins B, B' with the
perforated partition walls B' and the sieves B³, B3, in combination with the removable
covers B', B', the channels C, D and D¹ to D5, the rotary paddle wheels S, the
basins G with the parts G¹ G', the chanuels H, and the basins I, I having the
outlets K, all substantially as described with reference to the drawing.
In Witness whereof I the said Friedrich Petri lave bereunto set my hand
and seal this Twenty-eighth day of April in the year of Our Lord one
thousand eight hundred and eighty-three.