Raw Sewage.
Dissolved matter, grains per gallon.
Mineral.Organic and Volatile.Total.
33·033·066·0
Open Septic Tank Effluent.
Dissolved matter, grains per gallon.
Mineral.Organic and Volatile.Total.
30·825·055·8
Reduction, in per cent.
6·6724·2415·45

“A certain amount of loss of ammonia, as ammonium carbonate, will take place on evaporation in both cases, and this will probably be greater with septic tank effluent.

"An examination of the residue obtained by evaporating large quantities of open septic tank effluent (filtered through paper), shows that the mineral matters largely consist of iron oxide, from the decomposition of organic compounds of iron, and calcium sulphate. Among the volatile constituents have been detected ammonium carbonate, mercaptan-like compounds of very offensive smell, acetic and butyric acids. No evidence of the presence of amines could be found in the residue on evaporation, but by distilling large volumes of the liquid and carefully analysing the platinum salts obtained from the distillate, the presence of amines is indicated.

"Research in this direction is being continued; careful comparison especially will be made of the products obtained by evaporation and distillation of crude sewage and septic tank effluent respectively.

"The evidence, however, points to a breaking down of albuminoid and cellulose matter in the septic tank into simpler and to some extent volatile compounds. The reactions are probably hydrolytic in character, ammonia, amines, carbonic acid, water, and possibly alcohol, being produced.

"A further quantity of organic matter also disappears as methane, nitrogen and hydrogen.”

Must aerobic fermentation in all cases be preceded by anaerobic fermentation?

It will be clear from the foregoing, that the changes going on in a septic tank are entirely different from those brought about in contact beds, and the question whether a septic tank is a necessity for the subsequent contact bed treatment, or whether it is a distinct disadvantage, can only be definitely settled when we know

whether aerobic fermentation, i.e. decomposition, must in all cases be preceded by anaerobic fermentation, i.e. putrefaction, and to what extent, or whether such a succession of changes is not necessary.