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of Alkali, etc., Works who kindly co-operated with the Council's officers although
the matter, being concerned with offensive liquid effluent, was not strictly within
his jurisdiction.
Oil investigation the accident was attributed to oxides of nitrogen being carried
into the sewers in solution from nitric washing towers. Under normal conditions
the bulk of the nitrogen oxides evolved in the industry is recovered for re-use,
only traces being permitted to run to waste. It appeared, however, that owing to
pressure of work the capacity of the recovery system was overtaxed and a greater
proportion than usual of the nitrogen oxides reached the sewers. Steps were taken
by the proprietors of the works to neutralise the acid effluent and prevent
continuance of the trouble.
Notwithstanding this action the trouble recurred in November. Exhaustive
examination was therefore made of the interior of all the sewers in the vicinity of
the area affected and the effluents from the various drain connections were
examined. Information was obtained as to firms in the neighbourhood using acids
in the process of their business and special attention was given to the drain connection
from premises occupied by these firms, but the results were negative except
in the case of the works originally responsible.
The Chief Inspector of Alkali, etc.. Works again co-operated and on his
suggestion further steps were taken by the management of the works effectively
to avoid any recurrence of the dangerous conditions; a continuous stream of milk
of lime is being discharged into the effluent.
Recovery of Silver: Nuisance.
During 1931 numerous complaints were received from occupiers of premises in
the neighbourhood of Eed Lion Square regarding smells arising in the streets and
in some cases entering the houses. The smell, which was similar to that of
sulphuretted hydrogen, seemed to arise from the street gullies and ventilators.
The sewer in the street principally concerned is a pipe sewer with a dead end.
A sample of the sewage was submitted to the Public Analyst who reported that
it consisted mainly of sodium hyposulphite, a substance used largely in
photography.
Following this report all premises in the street affected were inspected but
in none was this chemical or anything similar used. It was then decided to trace
the drainage from premises in adjoining streets and eventually it was found that
the drain of a building in an adjoining street ran under premises at the rear into
the affected sewer. This building was occupied by a firm who were treating the
waste products from photography to recover the silver and turning the waste
effluent into the drain. This was found to be the cause of the nuisance.
The attention of the firm was drawn to the nuisance and they immediately
agreed to seek advice as to the best method of abating it. The Public Analyst
advised certain treatment which was adopted with excellent results. One
complaint as to the smell was subsequently received, in March, 1932, and a slight
modification was then made in the treatment. Since that time no nuisance has
been experienced.