Larry -
Conceptually, temperature-adjusted specific gravity of dilute sewage should vary primarily with the specific gravity of the raw water supply. Variance - generally within the range 1 to 1.02 - is almost invariably upward as a result of dissolved solids. Waste streams expected to provide disproportionate increase of specific gravity in comparison to traditional measurements (suspended solids and oxygen demand) include water softening brines, industrial or food processing brines, and sewer system infiltration from saline groundwater. Chlorination and dechlorination will slightly increase the specific gravity of secondary treated effluent. =puritan=
