PERFORMANCE OF SWINE WASTE LAGOONS FOR REMOVING SALMONELLA AND ENTERIC MICROBIAL INDICATORS

Abstract

Swine lagoon liquid may contain numerous pathogens at concentrations that are a risk to human health throughonfarm contact or through offfarm exposure, such as may occur if the pathogens are transported to ground or surface waterresources through seepage or spray irrigation. In this study, liquid samples were collected yearround from lagoons on fourswine farms and analyzed for Salmonella and six microbial indicators of fecal contamination (fecal coliforms, E. coli,enterococci, Clostridium perfringens spores, somatic coliphages, and Fspecific coliphages). Salmonella were measured atmean concentrations of 3.1 to 4.0 log10 MPN/100 mL in untreated flushed swine waste, 2.2 to 2.4 log10 MPN/100 mL insinglestage primary lagoon liquid, and 0.4 to 0.7 log10 MPN/100 mL in the secondary lagoons of twostage lagoon systems.Salmonella, fecal coliforms, E. coli, enterococci, somatic coliphages, and Fspecific coliphages were reduced by 1 to 2 log10in singlestage lagoon systems, and by 2 to 3 log10 in twostage lagoon systems. C. perfringens spore reductions weresignificantly lower than for the other microbes analyzed in primary treatment lagoons (mean reductions = 0.6 to 0.8 log10),suggesting that effective removal of environmentally persistent pathogens such as helminths and protozoan parasites(e.g., Cryptosporidium parvum) may necessitate the use of twostage lagoon systems, or alternative waste managementtechniques. Temperature was significantly associated with treatment efficacy for reductions of fecal coliforms and coliphagesin at least one of the primary lagoons studied. In secondary lagoons, temperature was significantly associated with reductionsof all the study microbes. Linear regression analysis of Salmonella reductions versus temperature in the secondary lagoonsyielded an r2 = 0.66. Based on statistical analysis of the magnitudes and correlations of their reductions, fecal coliforms andE. coli were determined to be the best microbial indicators of the reduction of Salmonella in swine waste lagoon systems. Theresults of this study indicate that singlestage, primary lagoons can substantially reduce concentrations of Salmonella, fecalcoliforms, E. coli, enterococci, and coliphages in flushed swine waste, but were not effective for reducing concentrations ofC. perfringens spores. Salmonella and other microbes can be further reduced in twostage lagoon systems, yielding overallenteric microbe reductions that are more protective of public health.