Fate of indicator microorganisms, Giardia and Cryptosporidium in subsurface flow constructed wetlands

Limited information is available on the ability of subsurface flow wetlands to remove enteric pathogens. Two multi-species wetlands, one receiving sec ondary sewage effluent and the other potable (disinfected) groundwater were studied from February 1995 to August 1996, at the Pima County Constructed Ecosystems Research Facility in Tucson, Arizona. Each wetland had a retenti on time of approximately 4 days. The objectives of this study were (1) to e valuate the ability of multi-species subsurface wetlands to physically remo ve Giardia cysts; Cryptosporidium oocysts, total and fecal coliforms, and c oliphages; and (2) to determine the likely impact of local wildlife on the occurrence of these indicators and pathogens. In the wetland receiving seco ndary sewage effluent, total coliforms were reduced by an average of 98.8% and fecal coliforms by 98.2%. Coliphage were reduced by an average of 95.2% . Both Giardia cysts and Cryptosporidium oocysts were reduced by an average of 87.8 and 64.2%, respectively. In the wetland receiving disinfected grou ndwater, an average of 1.3 x 10(2) total coliforms/100 mt and 22.3 fecal co liforms/100 mt were most likely contributed by both flora and fauna. No par asites or coliphages were detected. (C) 2001 Elsevier Science Ltd. All righ ts reserved.