VPE 511: Environment and Environmental Hygiene (2+1)

COMPOSITION AND STRENGTH OF SEWAGE

• Sewage is a mixture of saline matter in solution and nitrogenous and carbonaeous organic matter in solution and suspension together with a certain amount of grit and mineral matter.
• The strength of an ordinary domestic sewage depends on the amount of water used per head of population. If there are industrial wastes the strength will usually be increased.
• These are of course great variations daily, seasonal and those due to storm water. Industrial wastes such as those from breweries, gas works and dairies etc introduce additional complications.
• Chemical analyses of sewage usually indicted in parts of 100,000 (1) The solids in suspension and in solution (2) organic nitrogen, ammonical and albuminoid (3) Chlorides and (4) Quantity of oxygen required for oxidation of the organic matter to produce a non putrefactive effluent.
• In the sewage settling solids will be about two third of the total. About three fourths of the total suspended solids would be organic. The non settling solids are in a very fine state of division or in colloid form. The total suspended matter appears to be very small in the sewage.