|Thurston Enriquez, Jeanette|
Submitted to: Water Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2000
Publication Date: N/A
Citation: Interpretive Summary: Manmade wetlands, or constructed wetlands, are a low-cost alternative to traditional wastewater treatment. In the current study, the ability of a subsurface flow constructed wetland to reduce the number of pathogenic microorganisms from the incoming, partially treated, wastewater was studied. The water flowed through the wetland with a retention time of approximately 4 days. A second subsurface flow constructed wetland, receiving potable (disinfected) ground water, was studied in order to determine the number of pathogens that are introduced by indigenous plants and animals. The concentration of protozoan parasites, Giardia and Cryptosporidium, and indicator microorganisms, total coliforms, fecal coliforms and coliphage, were determined in the influent and effluent of both studied wetlands. Indicator microorganisms may be an indication of microbial water quality or may suggest the presence bacterial or viral pathogens in the assayed water sample. In the wetland receiving wastewater, 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 %. Giardia and Cryptosporidium were reduced by an average of 87.8 and 64.2 %, respectively. In the wetland receiving disinfected groundwater, an average of 1.3 x 102 total coliforms/100 mL and 22.3 fecal coliforms/100 mL were most likely contributed by flora and fauna surrounding the wetland. No protozoa or coliphages were detected.
Technical Abstract: Limited information is available on the ability of subsurface flow wetlands to remove enteric pathogens. Two multi-species wetlands, one receiving secondary 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 retention time of approximately 4 days. The objectives of this study were (1) to evaluate the ability of multi- species subsurface wetlands to physically remove Giardia cysts, Cryptosporidium oocysts, total and fecal coliforms, and coliphages; and (2) to determine the likely impact of local wildlife on the occurrence of these indicators and pathogens. In the wetland receiving secondary 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 1.3 x 102 total coliforms/100mL and 22.3 fecal coliforms/100mL were most likely contributed by both flora and fauna. No parasites or coliphages were detected.