COMPLETE PURIFICATION OF SEWAGE FROM ORGANIC MATTER
Year: 1885

page_text: I, JOHN HOWARD KIDD of Wrexham in the County of Denbigh, Engineer do
hereby declare the nature of my invention for THE COMPLETE PURIFICATION OF
SEWAGE FROM ORGANIC MATTER, to be as follows:-
I treat the effluent water in preference to the crude sewage, with a mixture of
5 slacked lime, soap and ferrous sulphate, to effect a thorough oxidation of the.
sewage and eliminate the sulphur from the sulphides formed by its decomposition.
JOHN HOWARD KIDD.
COMPLETE SPECIFICATION.
The Complete Purification of Sewage from Organic Matter.
I, JOHN HOWARD KIDD of Wrexham in the County of Denbigh, Engineer do
hereby declare the nature of my invention for THE COMPLETE PURIFICATION OF
SEWAGE FROM ORGANIC MATTER, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement :-
After extracting the bulk of the solid matter from the sewage by natural
subsidence on the quiescent principle I treat the supernatant water by adding to it
a solution of the following ingredients-
20 parts by weight of protosulphate of iron, 4 parts quicklime 1 part refuse or
spoilt soap.
The reason I use so little lime is, that I find the organic matter in the sewage
will settle faster in a neutral than in an alkaline solution. The soap is added to
assist in producing a second deposition. The action is as follows-The lime oxide

page_text: '
converts the protosulphate into a mixture of suboxide and hydrated sesquioxide of
iron, which body possesses the peculiar property of eliminating the sulphur from
the sulphide compounds (which are generated by the decomposition of all animal
sewage) combining with the sulphur and forming a black sulphide of iron, which
is perfectly innocuous. This reaction renders all smell of sulphuretted hydrogen
gas impossible. The soapy matter acts as a coagulating medium, because the fatty
acids in the soap combine with any excess of lime and form a gelatinous lime soap,
which assists in carrying down mechanically the suspended precipitating organic
matter and other bodies.
Or by another process I use about 10 lbs (finely divided in suspension) of bog
iron ore or "brown iron ore" or so called limonite or brown hematite and no lime.
Either of these processes will produce a good effluent for irrigating a limited area
of land, but where this is impracticable and the effluent must be passed direct from
the settling tanks into the nearest watercourse I then supplement this treatment
by adding about 7 lbs of permanate of soda (or potash) to each million gallons of
sewage.
Or about 2 lbs of bichromate of soda (or potash) and sulphuric acid, in order to
destroy the organic, carbonaceous & nitrogenous matters present. When using the
bichromates I always dissolve them in water and add a slight excess of sulphuric
acid.
In some cases I use about 2 lbs of chromic acid (in water) to destroy the soluble
organic matters present-in the said effluent always using a slight excess of sulphuric
acid with the chromic acid solution before adding it to the effluent water.
"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
"
1. The previous preparation of hydrated sesquioxide of iron in the manner set
forth and indicated for the purpose of purifying the sewage and taking out the
sulphur compounds.
2. The use of one or other of the bichromates with sulphuric acid for oxidising
and destroying the organic, carbonaceous and nitrogenous matters as set forth
and indicated.
3. The use of a solution of chromic acid in water acidulated with a slight
excess of sulphuric acid for the purpose of oxidising the organic, carbonaceous
and nitrogenous matters.