Dry and wet weather microbial characterization of the Chicago area waterway system G. Rijal, C. Petropoulou, J. K. Tolson, M. DeFlaun, C. Gerba, R. Gore, T. Glymph, T. Granato, C. O’Connor, L. Kollias and R. Lanyon ABSTRACT G. Rijal (corresponding author) R. Gore T. Glymph T. Granato C. O’Connor L. Kollias R. Lanyon Metropolitan Water Reclamation District of Greater Chicago, Chicago IL, USA G. Rijal Environmental Monitoring & Research and Development Department, 6001 West Pershing Road, Cicero Illinois 60804, USA E-mail: geeta.rijal@mwrd.org C. Petropoulou J. K. Tolson M. DeFlaun GeoSyntec Consultants, Chicago IL, USA C. Gerba University of Arizona, Tucson AZ, USA The Chicago Area Waterway System (CAWS) is a man-made channel, which serves the Chicago area for the drainage of urban storm water and the conveyance of secondary treated effluent from the Metropolitan Water Reclamation District of Greater Chicago’s (District) North Side, Stickney and Calumet water reclamation plants (WRPs). A microbial characterization of the CAWS upstream and downstream of the WRPs and from the WRP outfall was initiated by collecting dry and wet weather samples and analyzing for indicators and pathogens. During dry weather, indicator bacteria (fecal coliform [FC], E. coli [EC], enterococci [EN]) were the most abundant microbial species detected in the CAWS compared to pathogens (Salmonella spp [SA], enteric viruses [EV], adenovirus [AV], norovirus [NV] and Giardia and Cryptosporidium). Pseudomonas aeruginosa [PA] levels in the outfall samples were either lower or equivalent to the CAWS. The wet weather samples had a higher frequency of detection of indicator bacteria and pathogens compared to dry weather samples. Overall, the concentrations of pathogens in the CAWS, representing the weather conditions experienced in a recreational year, were relatively low. The study concluded that the presence of pathogens in the CAWS downstream of the WRPs were due to secondary loading of the waterway under wet weather conditions from combined sewer overflows (CSOs) and other discharges. Key words | bacteria, dry and wet weather, pathogens, protozoa, viruses INTRODUCTION The District is located within the Midwest region of the United States and serves an area of 883 square miles, which includes the City of Chicago and 125 suburban commu- nities. The District serves an equivalent population of 10.35 million people. The District owns and operates one of the world’s largest WRP (Stickney), in addition to six other plants, and treats an average of 1.4 billion gallons of wastewater each day. The secondary treated wastewater effluents from North Side, Stickney and Calumet WRPs are discharged into the Chicago Area Waterway System (CAWS). The CAWS consists of man-made canals and/or natural water bodies that have been irreversibly modified for two principal purposes, the drainage of urban storm water runoff and treated WRP effluent, and the support of commercial navigation (District 2008). The CAWS is also used for recreational boating, canoeing, fishing and other streamside recreational activities. Swimming and other primary contact recreation is not a designated use of the waterway. About 70 percent of the annual flows in the CAWS are from the discharge of secondary treated municipal wastewater effluent from the District’s three major WRPs (District 2008). Currently, there are no microbial water quality criteria for the CAWS. This study was initiated to generate the scientific information necessary to understand the public health uncertainties in the CAWS. The primary objective of this doi: 10.2166/wst.2009.598 1847 Q IWA Publishing 2009 Water Science & Technology—WST | 60.7 | 2009 Downloaded from https://iwaponline.com/wst/article-pdf/60/7/1847/448589/1847.pdf by guest on 06 June 2020