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ASSESSMENT OF AN INFILTRATION BASIN AND CONSTRUCTED WETLAND FOR REMOVAL OF PATHOGENS FROM FEEDLOT RUNOFF
Citation:
ROGERS, S. AND J. R. HAINES. ASSESSMENT OF AN INFILTRATION BASIN AND CONSTRUCTED WETLAND FOR REMOVAL OF PATHOGENS FROM FEEDLOT RUNOFF. Presented at Annual Meeting of the Soil and Water Conservation Society, Tampa, FL, July 23 - 25, 2007.
Impact/Purpose:
to present information
Description:
The use of an infiltration basin and constructed wetland to treat process wastewater from a cattle feedlot prior to discharge to an adjacent waterway was explored in regards to fecal pathogens. Weekly sampling of typical operating conditions and rainfall-generated runoff during 21 events of varying magnitude were monitored to identify movement of microorganisms through critical points in the study system and the impact on water quality in the receiving stream. On average, the treatment system was challenged with 6.5 X 106 E. coli, 5.8 X 106 enterococci per 100 mL. During periods of low (non-event-based) flow, there was a 3-4 log reduction in E. coli and enterococci in the infiltration basin, but negligible treatment in the constructed wetland. Elevated flow through the system caused by rainfall-generated runoff resulted in washout of the infiltration basin and constructed wetland and discharges of E. coli and enterococci to the receiving stream averaging 3.2 X 106 and 2.8 x 106 per 1O0mL, respectively. Pair-wise comparison of the most probable numbers of E. coli and enterococci upstream and downstream of the discharge point for the constructed wetland was performed for times that the wetland was discharging. It was determined that discharge from the system had a negative impact on water quality, increasing E. coli populations significantly downstream relative to upstream (N=lO, a=0.05). In contrast, pair-wise analysis of all sample points in which the constructed wetland was not discharging, including rainfall events, suggests no change in either E. coli or enterococci concentrations (N=34, a=0.05). Why is this significant? We have detected genetic virulence indicators for E. coli 0157:H7 (eaeA, stxl, and stx2) and Salmonella (ttrC, and invA) as well as multi-drug resistant fecal bacteria including vancomycin-resistant enterococci (VRE) in the process wastewater. Our preliminary results suggest that this infiltration basin and constructed wetland system may not sufficiently remove these pathogens from the waste stream, especially during rainfall. We intend to report on our findings regarding the transmission of E. coli 0157:H9, Salmonella, and antimicrobial-resistant bacteria through the treatment system as well as the concurrent movement of quantitative source specific molecular biomarkers for cattle fecal pollution.