Reduction of enteric microbes in flushed swine wastewater treated by a biological aerated filter and UV irradiation.

Abstract

An aerobic biofilter system was studied to assess its effectiveness for reducing enteric microbial indicators in flushed swine wastewater under different seasonal conditions. A laboratory-scale, low-pressure UV collimated beam apparatus was used to investigate the effectiveness of UV irradiation for inactivating enteric bacteria, coliphages, and bacterial spores in treated and untreated swine wastewater having unfiltered absorbances of 5 to 11 cm(-1) and total suspended solids concentrations of 500 to 1200 mg/L. Fecal coliforms, Escherichia coli, enterococci, somatic coliphages, and male-specific coliphages were reduced by 97 to 99% in the biofilter system when reactor water temperatures were between 23 and 32 degrees C. Salmonella were reduced by 95 to 97% when water temperatures were 17 to 32 degrees C. Of the six microbial indicators studied. Clostridium perfringens spores were typically reduced the least by the biofilter system. At an average absorbed UV irradiation dose of 13 mJ/cm2, maximum reductions of fecal coliforms, E. coli, enterococci, C. perfringens spores, and somatic coliphages in biofilter system effluent were 2.2, 2.1, 1.3, 0.2, and 2.3 log10, respectively. The results of this study show that the aerobic biofilter system can be an effective alternative for treatment of flushed swine waste. Ultraviolet irradiation can be effective for further reducing enteric microbe concentrations in biologically-treated swine waste, as well as in lower quality wastewaters, indicating its general potential for pathogen reductions in low-quality wastewaters intended for beneficial reuse.