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The substances which had to be dealt with under the head of 
Sewage purification might be conveniently classified as follows :— 
First, solid faeces consisting of nitrogenous, partly digested 
matter, together with vegetable non-nitrogenous residues of 
food; second, urine, which was the main source of the ammonia 
found in sewage; thirdly, household waste, containing vegetable 
refuse, etc., fragments of animal food, soap water, etc.; fourth, 
rain and storm water, consisting of street washings ; fifth, grit 
and detritus ; and sixth, manufacturing waste products. 
The primitive method of disposal was either by burning or 
covering with earth, and a partial return to the latter was seen in 
the adoption of various systems of land irrigation. The Lecturer 
pointed out different modifications of this system, and mentioned 
that at Burnley the method practised, previous to the adoption 
of the present system, was that of having mixed systems, 
including previous sedimentation by chemical preparation. 
Dealing with the land at Wood End Sewage Works, belonging 
to the Corporation, he said the heavier portions of the land were 
eminently unsuitable for the treatment of Sewage or any sewage 
farm principle, but readily lent themselves to adaption for 
bacterial filters, the stiff clay forming an excellent material for 
banks and bottoms, thus saving the expense of brick and 
concrete. 
He explained how the Sewage was treated at the Duckpits 
Sewage Works, and speaking of the contact beds, said they all 
knew very well the offensive smell caused by stagnant Sewage or 
putrefying organic matter, and pointed out that one of the main 
objects of purification was to so purify the Sewage that an 
effluent incapable of putrefaction was obtained. This they had 
succeeded in doing at Burnley, and they were enabled to prove 
it by placing a small quantity of Sewage in a bottle and keeping 
it for several days in an incubator, when, if no sulphurretted 
hydrogen, or objectionable odours were given off, the Sewage 
might be considered non-putrescent. 
The works at Duckpits and Wood End dealt with the Sewage 
from an area populated by 80,000 people, and the dry weather 
flow was about 2,000,000 gallons per day. The other Corpora- 
tion works at Altham treated the Sewage from a population of 
about 20,000, with a dry weather flow of about 350,000 gallons 
per day. 
Whether any specific advantage was to be obtained by the use 
of a closed Septic tank as opposed to an open one was still some- 
what doubtful, opinions differing very much upon the subject, 
the composition of the particular Sewage under treatment being 
a very important factor. It must be remembered that the 
