Emerging Implications of Systematic Balancing of Disinfection and Primary Treatment as an Element of US Practice and Policy in CSO Control: 1. Model Requirements

This paper describes early results and directions arising from ongoing research into factors that affect the preferred balance between primary treatment and disinfection in a conventional wastewater treatment plant during periods of wet weather overflow. Despite the fact that national policy and regional regulations have required or implied use of these elements of treatment for decades, there remain some basic issues that are unresolved. In the context of a wet weather overflow event, the selection of an optimum point and manner for disinfection as it relates to the degree solids removal is one such issue. The factors that affect the choice of this point, particularly as reflected by the current state of microbiological understanding of quantification methods and of the influences of water chemistry on disinfectant behavior and indicator bacteria partitioning between solid and liquid phase components of the flow stream, are examined. Potential avenues for improved treatment practices are noted, and research directions are discussed.