Comparison of Fecal Coliform Concentrations and Trends in a Secondary Contact and General Use Urban River
Abstract:To assess the water quality management goal for the Lower Des Plaines River (LDPR), the Metropolitan Water Reclamation District of Greater Chicago (District) developed a cooperative relationship with the Illinois Environmental Protection Agency (IEPA) to generate information on the potential recreational use classification of the LDPR. It was apparently assumed that the District water reclamation plants (WRPs) were the dominant sources of FC reaching the LDPR. District recognized that a thorough understanding of the trends and variations of FC concentrations both in the Des Plaines River (DPR) and the Chicago Sanitary and Ship Canal (CSSC) are required before sound recommendations regarding the microbial quality and recreational potential of the LDPR can be made. A study was designed to compare the fecal coliform bacteria data collected from the General Use LDPR upstream of Lockport with the effluent dominated CSSC at Lockport for the 2000-2001 period. Weekly data for fecal coliform (FC) bacteria and other potential factors such as river flow, rainfall, storm-period, temperature, total suspended solids and turbidity were also included to determine the statistical differences between fecal coliform densities in CSSC and DPR under dry and wet weather conditions. The overall regression analyses results showed that the concentrations of FC bacteria in the General Use DPR, upstream of Lockport, and at the CSSC at Lockport were not significantly different. Similar results were obtained when wet weather conditions and seasonal disinfection periods were looked at separately. Variations in FC concentration did not correlate to other water quality parameters such as, temperature, rainfall, total suspended solids and turbidity that can be monitored on a real-time basis. The DPR (91), which receives seasonally disinfected wastewater effluent from upstream suburban communities, had a higher percentage of FC concentrations that exceeded the General Use advisory limit of 200 CFU/100 mL than CSSC (92) which is dominated by non-disinfected treated effluents from the District's Stickney, North Side and Calumet WRPs. It is concluded that the microbial quality of the CSSC at Lockport, which is classified as Secondary Contact water, was comparable to the microbial quality of the DPR at Lockport, which is classified as General Use water. This finding indicates that the secondary treated effluents from District WRPs, discharging into the CSSC upstream of Lockport, are not adversely affecting the microbial quality of the DPR downstream of Lockport. Therefore the practice of disinfection at District WRPs may not necessarily result in reducing the FC burden in the LDPR and calls into question the efficacy of the practice of seasonal disinfection in the DPR watershed. The sources for FC bacteria in LDPR may be environmental/non-point sources (storm drains, geese, animal feces, soil run-off and sediment). The extent to which the non-point sources (of fecal coliform) are affecting the water quality needs to be considered for the recreational classification of the LDPR.
Document Type: Research Article
Publication date: 2009-01-01
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