Moline River Diffuser and Chlorination Improvements

Moline River Diffuser and Chlorination Improvements

Challenge

The City of Moline had to meet new total residual chlorine (TRC) limits at its South Slope Wastewater Treatment Facility.

Solution

Alternate disinfectants and chemical dechlorination systems were evaluated. The city chose construction of a diffuser in the Rock River, along with improved chlorine controls. The diffuser mixes the chlorinated effluent with river water so that chlorine concentrations are not harmful to aquatic life. This was the first use in Illinois of a river diffuser to control total residual chlorine (TRC) and ammonia. The project uses a variety of new disinfection technologies, including oxidation-reduction potential (ORP) control monitoring and gaseous chlorine inducton to optimize the disinfection process.

Impact

By mixing the plant discharge over a wide section of the river, the city could meet both TRC standards and ammonia restrictions without major modifications to its treatment processes. This solution also enabled the city to meet future ammonia restriction economically. The improved control system has reduced chlorine use from around 180 pounds per day before the project to 40 pounds per day. The diffuser and controls were put into service two months prior to the compliance date required by the Illinois Environmental Protection Agency.

This project received an honor award from the Consulting Engineers Council of Illinois and was named a finalist in American Consulting Engineers Council's Engineering Excellence Awards competition.
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