Microbial Water Quality Monitoring of Stormwater and Reclaimed Water to be Used for Rehydration of Stressed Wetlands and Lakes

The City of St Petersburg owns and operates the Section 21 Wellfield, which is located on 583 northwest Hillsborough County. Wetlands and lakes comprise approximately half of the land within the Section 21 Wellfield. During the past several years due to both climatic changes (drought) and man's activities (development and pumpage), these wetlands have experienced diminished hydroperiods with the lakes at or near historical low water levels. In addition, heavy rains associated with the El Niño phenomenon (late 1997 and early 1998) have raised surface water levels within the wellfield near their historic highs that has provided a baseline condition to which the planned low volume rehydration would maintain appropriate levels in a natural fashion. The City recommended using the Section 21 Wellfield as the site for a pilot project to test the effectiveness of rehydrating stressed wetlands and lakes within and adjacent to a wellfield with stormwater and/or reclaimed water. The objective of this work is to asses the microbial quality of these two sources of water in terms of; bacterial indicators, coliphages, Cryptosporidium and Giardia in order to determine its impact on the water quality of wellfield's surface and groundwater systems as well as the associated level of possible public health consequences. The study also includes the characterization of surface and ground water systems within the wellfield and other water features that may impact the wellfield. Preliminary data demonstrated that the level of bacterial indicators such as fecal coliforms and total coliforms in three of the lakes sampled were above the water quality standard established by the Florida Department of Environmental Protection for ambient waters (800 CFU/100 mL and ≤2400CFU/100 mL, respectively). Clostridium perfringens was detected in surface water samples ranging between 6 and 85 CFU/100 mL. Enterococci were detected at levels above the standard microbiological guideline established by United Sates Environmental Protection Agency for ambient waters (104 CFU/100 mL). The level of bacterial indicators in reclaimed effluent and groundwater samples was very low and in most of the cases less than the limit of detection. Coliphages have not been quantified by the current agar overlay method in any of the samples collected, however, they have been detected in stormwater and one lake using the enrichment protocol. Cryptosporidium oocysts were detected at levels of 0.1/100 L and 0.53/100 L (groundwater) 19.2 and 112.7/100 L (surface water), 1.91 and 6.50/100 L (reclaimed effluent) and 287.67/100 L (stormwater). Giardia cysts were detected at levels of 1.46/100 L (groundwater) and 3.75/100 L (surface waters).