ABSTRACT
Wet-weather flow has been shown to be a significant contributor to microbial contamination of receiving waters (see Chapter 1). The presence of pathogens in SW and CSO, as well as their potential release into receiving waters, is the main reason for growing interest in the area of WWF disinfection. The National CSO Control Policy issued by the U.S. EPA recommends CSO disinfection after primary treatment in areas where disinfection is required by local authorities (U.S. EPA 1994). The use of Cl
in wastewater disinfection has been accepted for many decades. Although, to date, Cl
is the primary disinfection agent used for wastewater treatment in the U.S., chlorination poses serious risks to aquatic ecosystems. Because of the high flowrates and volumes of WWF, proper treatment often requires high Cl
concentration and thus results in a high level of toxic byproducts and Cl
residuals in receiving waters. The discovery of the link between chlorination byproducts and potential adverse effects on human health and aquatic life has raised questions about the safety of chlorination. Increasing environmental regulations
requiring disinfection and a growing awareness for the safety of environmental actions motivate the search for a Cl
replacement. Alternative disinfectants, e.g., ultraviolet (UV) light, chlorine dioxide (ClO
) and ozone (O
), are strong agents that generate significantly fewer toxic byproducts and residuals than Cl
. The alternative disinfectants used for CSO should be efficient and cost effective, safe to handle and should not produce hazardous or toxic byproducts (Aieta et al. 1980). This chapter emphasizes their feasibility for CSO applications.
