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EPA Compliance Reached Through Fort Madison CSO Project The U.S. Environmental Protection Agency issued a Consent Order requiring the City of Fort Madison to address combined sewer overflows (CSOs) by either implementing disinfection of CSOs or eliminating them. Learn More
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Disinfection Key in Keeping Combined Sewer Overflow Discharge Safe for the Mississippi

Stanley Consultants prepared contract documents for Fort Madison, Iowa, for the construction of a full-scale pilot sewer demonstration system. 

Fort Madison, Iowa, founded in 1808, is just one of over 700 older cities in the U.S. that operates a combined sewer system.  Collecting sanitary sewage and stormwater runoff in a single pipe system becomes problematic when large variations in flow between wet and dry weather can cause the sewer to overflow.  In the case of Fort Madison, during heavy rains eight combined sewer overflow (CSO) structures discharge directly into the Mississippi River.

The City entered into a Consent Order with the U.S. Environmental Protection Agency.  It required either a pilot study to determine the feasibility of disinfecting the CSOs and subsequent installation of a disinfection system at the City's combined sewer overflow structures, or elimination of the CSOs.  The City chose to disinfect the CSOs to reduce E. Coli bacteria to regulatory-required levels and sought the assistance of Stanley Consultants to study the CSO system and design a disinfection system.

The study concluded that chemical disinfection using sodium hypochlorite or peracetic acid was the most viable technology for disinfecting the CSOs.   

Stanley Consultants prepared contract documents for construction of a full-scale pilot demonstration system.  Highly variable flows, highly variable solids concentrations, and limited site space for contact basins presented challenges for the technology to appropriately disinfect the flows.  Development of a monitoring plan, permitting, bidding and construction phase services, and regulatory reporting were included.  Stanley Consultants will assist the client with operational adjustments and troubleshooting during system start-up.

A one-year demonstration period will follow start-up of the pilot plant.  The City will collect electronic data on flow metering, sampling results, and other operational parameters from the pilot system.  Stanley Consultants will then review and evaluate the data for system effectiveness with results presented in report form.

The pilot study will reduce bacteria in wet weather combined sewer overflows and improve water quality in the Mississippi River.  The pilot study may also demonstrate the feasibility of disinfecting combined sewage that can be used by other combined sewer overflow communities.