Wednesday, November 7, 2007
325-14
Survival, Transport, and Source Tracking of Enteric Bacteria in Soils of a Municipal Park Irrigated with Reclaimed Wastewater.
Jean McLain1, Clinton F. Williams1, Channah M. Rock2, and Sharette Evans1. (1) USDA-ARS, US Arid-Land Agricultural Research Ctr, 21881 North Cardon Lane, Maricopa, AZ 85238, (2) Department of Soil, Water, and Environmental Science, University of Arizona, Maricopa Agricultural Center, 37860 W Smith-Enke Road, Maricopa, AZ 85238
Increasing demands on limited water resources have made wastewater reclamation for municipal irrigation an attractive option for extending available water supplies. However, there remain public health concerns about the potential risks to humans coming into contact with irrigated turf areas. We are monitoring soil and water quality in a municipal city park in Maricopa, Arizona , where turf has been irrigated with reclaimed water since the opening of the park in September 2006. The presence of viable E. coli and Salmonella in the irrigation system, and in an adjacent pond where reclaimed irrigation waters are held prior to application, are being monitored using standard plating methods. Bacterial transport and survival from the soil surface to a depth of 15 cm is being determined through plating of subsamples obtained from soil cores. Through the first nine months of the study, E. coli and Salmonella levels in the reclaimed water leaving the treatment plant remained within regulatory guidelines (< 0.02 CFU mL-1). Salmonella levels were higher in the pond and in the irrigation system, averaging 1.3 x 102 CFU mL-1, while E. coli levels averaged < 0.3 CFU mL-1. However, the pond is stocked for recreational fishing and also serves as a haven for waterfowl, and while Salmonella tend to be associated with warm-blooded animals, they are commonly detected in fish guts, while both fish and birds can harbor E. coli. We are using quantitative real-time PCR and Bacteroides-specific primers to both quantify and differentiate the sources of bacteria (human vs. other) in the pond and irrigation water. Our early results indicate that E. coli and Salmonella may be surviving in the soil after application but as of yet, we have found no bacterial transport downward in the soils (and thus, no potential for pollution of groundwater). By identifying the sources of bacteria and the transport and survival of E. coli and Salmonella within the parkland, this work will reveal potential impacts, including ecological benefits, of using reclaimed water for municipal irrigation.