An Improved Method of Purifying Sewage and other Foul Waters by Means of a Secondary Process following other Primary Processes
Year: 1897

page_text: Date of Application, 22nd July, 1897
Complete Specification Left, 22nd Apr., 1898-Accepted, 22nd Aug., 1898
PROVISIONAL SPECIFICATION.
An Improved Method of Purifying Sewage and other Foul Waters by
Means of a Secondary Process following other Primary Processes.
I, JAMES BURY PETRIE, of Tunshill House, Milnrow, near Rochdale, in the
County of Lancaster, Chemical Engineer, do hereby declare the nature of this
invention to be as follows:-
I cause the effluent from the primary process or settling tanks used in the
purification of sewage and other foul waters to pass over or otherwise come in
contact with soluble salts of iron in the ferric state by which means oxygen is
imparted to the putrescible matter held in solution in the effluent from the said
primary process or settling tanks thereby doing away with the necessity for large
area filtration.
In some cases in place of soluble ferric salts I may use soluble ferrous salts and
pass a current of electricity through a solution obtained from these soluble ferrous
salts either before or after mixing with the treated and settled effluent from the
settling tanks thereby converting the ferrous salts into ferric salts.
If ferric or ferrous salts are not used in the secondary process a current of
electricity may be passed through the treated and settled effluent from the settling
tanks in any ordinary manner.
If necessary after the treated and settled effluent has been sufficiently oxidised
by any of the aforementioned means it may be made to pass into a further
settling tank and allowed to settle until quite clear or it may be made to pass
through a sand or other approved filter bed or through a strainer.
Dated this 21st day of July 1897.
JAMES BURY PETRIE.
An Improved Method of Purifying Sewage and other Foul Waters by
Means of a Secondary Process following other Primary Processes.
I, JAMES BURY PETRIE, of Tunshill House, Milnrow, near Rochdale, in the
County of Lancaster, Chemical 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 following statement: —
I cause the effluent from the primary process or settling tanks used in the
purification of sewage and other foul waters which primary process as is well
Price 77

page_text: known consists in the removal of solid and visible matter from the sewage to be
treated to pass over in the secondary stage or process or otherwise come in
contact with soluble salts of iron in the ferric state such as Fе, Cl, or Fе, (SO4) 3
by which means oxygen may be imparted to the putrescible matter held in solution
in the effluent at this stage and chiefly or generally consists of invisible matter
which effluent passes in such state from the said primary process or settling tanks
thereby according to my invention dispensing with the use of or necessity for
large area filtration, thus greatly reducing the amount of ferric salts required,
and by this method of application at this stage a definite quantity of putrescible
matter in solution is dealt with, whereas in a primary process an indefinite quantity
of such matter is contained as is well known when the sewage emanates from
residences, works, or is towns' sewage thus having an indefinite quantity of
putrescible matter to treat but in a secondary process my method admits of an
adjustibility of components or the above compounds by which the sewage may
be treated.
In some cases instead of the employment of soluble ferric salts I may employ
for the carrying out of my invention soluble ferrous salts such as Fe, SO4, or any
other suitable ferrous salts and at any convenient stage of the said secondary pro-
cess may pass a current of electricity through the sewage so treated or solution
obtained either before or after mixing with the treated and settled effluent from
the settling tanks thereby converting a portion of the -ous salts into -ic salts
such as Fe,, (SO4) 3..
As an example of applying my process and quantities therein used or employed
and as before mentioned I proceed as follows.
By adding the ferric or ferrous salts at this stage i.e., the secondary process
stage I greatly lessen the amount required, as hitherto used, if 15 grains per gallon
were required in a primary process 2 to 5 grains would be sufficient if added as
a secondary process after all solids had been eliminated, also the absence of solids
makes it possible to adjust the ferric or ferrous salt to the required amount as above
mentioned whereas when added in a primary process as a precipitant in the
presence of solids the sewage changes so frequently and rapidly that a correct
adjustment is impossible.
Thus by the use of my process as herein indicated it will be seen that whether
ferric salts, or the electric current after the addition of ferrous salts, with rapid
filtration, or ferrous salts alone and slow filtration be employed the application
of these materials as a secondary process after all solids have been extracted greatly
facilitates the purification by lessening the amount required in a greater or lesser
degree according to the nature of the sewage such reduction varying from 1/5th
to 20th of the amount required to produce the same effect when added as a
primary process, and also assures adjustability of the required material the varia-
tion of the impurities in the sewage being only small after all solids have been
eliminated in any primary process before named.
If ferric or ferrous salts are not used in the secondary process a current of
electricity may be passed through the treated and settled effluent from the settling
tanks in any ordinary manner, i.e. by using iron plates for the positive and
negative poles the iron dissolved by the electric current is converted into a hydrated
ferrous oxide Fe O, H, which is a useful deodoriser. If carbon poles are used
the oxygen liberated by the decomposition of the water oxidises the putrescent
matter in the sewage. The advantages of applying the electric current at this
stage as a secondary process is the great reduction in the amount of current
required compared to what is necessary to produce the same effect if applied as a
primary process in the presence of suspended matter and also adjuustability of
the quantity of current required is attained.
If found desirable or convenient after the settled effluent has been treated by
any of the aforementioned means it may he made to pass into a
settling tank
previous to passing it through a sand or other approved filter bed or through a

page_text: strainer, the aeration thus obtained assists the subsequent purification in the
filter bed.
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:-
CLAIMS.
1. In a secondary process for the treatment of sewage and other foul waters
the application of a ferric salt for purification purposes whereby adjustability
is attained and large area filtration dispensed with as herein fully set forth.
2. The method and application of a ferrous salt partially converted into a ferric
salt by means of an electric current as and for the purposes herein set forth.
3. In a secondary process for the treatment of sewage the application of an
electric current whereby adjustability is attained and the putrescible matter in
solution is treated as herein fully set forth.
Data 10th love of I..).. 1000
JAMES BURY PETRIE.
J. H. Butterworth,
Rochdale, For the Applicant.