ABSTRACT
I N the past, chemical addition (to effect chemical precipitation) was used to enhance the degree of suspended solids and BOD removal (1) where there were seasonal variations in the concentration of the wastewater, (2) where an intermediate degree of treatment was required, and (3) as an aid to the sedimentation process (Metcalf & Eddy, 1991, p. 303). Currently, the need to provide more complete removal of the organic compounds and nutrients (phosphorous and nitrogen) contained in wastewater has brought about renewed interest in chemical addition. Chemical organic compounds and nutrients are also used in wastewater treatment for disinfection (see Chapter 13) and odor control.
