Monday, November 13, 2006

E. coli Regrowth in a Constructed Wetland Receiving Treated Sewage Effluent: A Threat to Human Health?.

Jean E.T. McLain1, Clinton F. Williams1, and Channah M. Rock2. (1) USDA-ARS, US Arid-Land Agricultural Research Center, 21881 North Cardon Lane, Maricopa, AZ 85239, (2) Ira A. Fulton School of Engineering, Arizona State Univ, PO Box 875306, Tempe, AZ 85287

Constructed wetlands are used throughout the world to filter toxins from treated wastewater and to increase wildlife habitat. Bird and mammal excretions result in background levels of enteric bacteria in any natural wetland, but regrowth of bacteria in wastewater effluent can further increase microbial loads, resulting in bacterial counts exceeding acceptable levels for regulatory permitting. Over 7 months, we investigated the presence of enteric bacteria (total coliform and E. coli) in tertiary-treated effluent as it passed through the Tres Rios Constructed Wetlands in Phoenix, Arizona. Our data confirmed the presence of seasonal bacterial blooms as high as 2400 CFU E. coli mL-1 and suggested that transmission of these bacteria to the surrounding waterways may have occurred. Six highly specific polymerase chain reaction primer sets were used to determine if E. coli found in the wetland waters were strains pathogenic to humans, or if these were nonpathogenic E. coli that would not pose harm to the surrounding environment. By determining the pathogenicity of E. coli regrowth in this the Tres Rios Constructed Wetlands, this work will aid in improved identification and control of disease-causing bacteria in managed wetland systems.


Handout (.pdf format, 169.0 kb)