Removal of Salmonella and microbial indicators in constructed wetlands treating swine wastewater

Abstract

Reductions of Salmonella bacteria and enteric microbial indicator organisms were measured in swine wastewater treated by a field-scale surface flow (SF) constructed wetland at a commercial hog nursery in North Carolina and in laboratory-scale SF and subsurface flow (SSF) constructed wetland reactors. Overall reductions of Salmonella, fecal coliforms and E. coli were 96, 98 and 99%, respectively, in the two-cell field-scale wetland. Somatic and F-specific coliphage viral indicators were reduced by 99 and 98%, respectively. Reductions of Salmonella, fecal coliforms and E. coli were similar in the first cell of the field system and in the laboratory-scale SF wetland operated at a TKN loading of 25 kg ha-1 d-1 and 30°C (approximately 70, 90 and 90%, respectively). In the SSF wetland reactor, Salmonella and fecal coliform reductions were 80 and 98%, respectively, at a 40 kg TKN ha-1 d-1 loading and 99.8 and 99.99%, respectively, at a 10 kg TKN ha-1 d-1 loading. These results show that SF constructed wetlands can be effective for reducing enteric pathogens in swine wastewater and that greater removals can be achieved using SSF designs and lower TKN loading rates.