Modeling chlorine-produced oxidant demand and dilution in chlorinated combined sewer overflow discharges
Combined sewer overflow (CSO) water introduces pathogens to receiving waters. To control pathogenic releases, chlorine may be added to disinfect CSO water. The added chlorine may react with water constituents to form oxidative species known as chlorine-produced oxidants (CPO). CPO are
the sum of free and combined oxidative species that form upon adding free chlorine-bearing compounds (e.g. gaseous chlorine or hypochlorite) to water. CPO discharge is often regulated by governing agencies. Current methods to model CPO behavior do not account for CPO decay and dilution simultaneously
in receiving water. This study creates a novel model for CPO demand and dilution in receiving water from chlorinated effluent in order to determine site-specific practices for implementation of a CSO water disinfection regime. To do this, representative receiving water was collected and dosed
with 1, 2, and 4 mg/L chlorine. The residual chlorine was measured at intervals up to 30 min after dosing. The immediate and subsequent chlorine demand was calculated, with the subsequent demand modeled by simultaneous application of dilution and decay using pseudo-first-order
decay kinetics. A comparison of model calculations indicates that application of dilution before decay underestimates CPO demand, while application of decay before dilution overestimates CPO demand.
Keywords: Combined sewer overflow (CSO); chlorine decay and dilution model; chlorine decay kinetics; chlorine-produced oxidants (CPO); pseudo-first-order decay
Document Type: Research Article
Affiliations: 1: Department of Civil and Environmental Engineering, Rutgers University, New Brunswick, New Jersey, USA; 2: Department of Civil and Environmental Engineering, Manhattan College, Riverdale, New York, USA; 3: Mott MacDonald, Iselin, New Jersey, USA
Publication date: 23 February 2020
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