The Chicago Waterways System (CWS) offers an array of recreational opportunities for the community. The Illinois Environmental Protection Agency (IEPA), in compliance with the Clean Water Act, is currently conducting a Use Attainability Analysis (UAA) on the CWS. One aspect of the UAA is to determine whether bacterial water quality standards for some or all of the CWS are necessary to protect the proposed designated uses of the CWS. In order to assist IEPA in making its determination, the Metropolitan Water Reclamation District of Greater Chicago (District) selected Geosyntec to conduct a risk assessment of the human health impacts of instituting effluent disinfection at its three largest water reclamation plants (WRP), which include the Stickney WRP, the North Side WRP, and the Calumet WRP, all of which discharge into the CWS.
Geosyntec's Scope of Services
Geosyntec developed and implemented a sampling, analysis and quality assurance plan for the microbial characterization of the CWS. In addition, Geosyntec developed a strategy for the conceptual evaluation of the implementation of disinfection technologies based on wastewater flow rates and available wastewater characteristics. The microbial sampling analytical results and the disinfection effectiveness results were incorporated into the microbial risk assessment for gastrointestinal and non-gastrointestinal illness due to selected bacterial, protozoa and viruses.
The risk assessment protocol included microbial hazard identification for selected pathogen; exposure assessment for accidental ingestion, body surface contact, and inhalation; determination of the minimal infectious dose from the peer-reviewed literature; characterization of the risk by conducting a separate risk assessment of the waterway segments downstream of each of the three WRPs; and quantifying the decrease, if any, in the incidence of disease if effluent disinfection was initiated.
Geosyntec's documented project findings to the District enabled the it and IEPA plan a course of future treatment options at the District's WRPs based on a range of field conditions and the application of innovative, proven risk assessment techniques.