ABSTRACT
This chapter identifies the aspects of wastewater treatment which can benefit from use of toxicant screening procedures. Toxic substances entering wastewater treatment plants can adversely impact the environment by upsetting the organic and nutrient removal functions of biological treatment processes or by escaping into receiving waters in excessive concentrations. Areas in which chemical toxicants can impact wastewater treatment plants include workers' health, biological processes, sludge disposal, and receiving water quality. Nitrification, the biological oxidation of ammonia to nitrate by autotrophic bacteria, is often required in wastewater treatment systems to achieve water quality goals such as ammonia or total nitrogen removal. The relationship between wastewater toxicity as measured by microbial assays and the effects of toxic constituents on the performance of biological treatment processes has been the subject of several investigations. Chlorine dosage in disinfection is normally established on the basis of measured coliform inactivation efficiencies. This procedure is ineffective when influent coliform concentrations or wastewater quality are changing rapidly.
