Removal of human enteric viruses and indicator microorganisms from domestic wastewater by aerated lagoons

Abstract

Aerated lagoons offer a low-cost and simple approach to treating domestic wastewater in small municipalities. The objective of the current study was to evaluate, for each cell in the lagoons, the removal of indicator microorganisms and human enteric viruses under warm (summer) and cold (early spring) conditions. The two sites are located in southwest Quebec, Canada. Samples were assayed for thermotolerant coliforms, enterococci, Clostridium perfringens, somatic and male-specific coliphages, and culturable human enteric viruses (HEV). The results show higher removal under warm ambient conditions for all microorganisms. Thermotolerant coliforms and enterococci were removed to a greater extent than C. perfringens and HEV. HEV removal was only observed in warm ambient conditions. The removal of coliphages was different from the observed removal of HEV. The use of coliphages as surrogates for HEV has been proposed, but this does not seem appropriate for aerated lagoons, as the removal of coliphages overestimates the removal of HEV. Given the low observed removal of HEV during this study, the effluents remain a significant source of pathogens that can affect drinking water treatment plants drawing their raw water from receiving streams. Ultraviolet disinfection of treated wastewater effluent is a possible solution.