M.E. Verbyla*, J.R. Mihelcic
Department of Civil & Environmental Engineering University of South Florida 4202 E. Fowler Ave. ENB 118 Tampa, FL 33620 – USA(free)
ABSTRACT There is lack of consensus in the literature regarding the extent of virus-particle associations in waste stabilization ponds (WSPs) and the implications for virus removal. In this study, the associations of F+ coliphage (measured with the double agar layer plaque assay) and human adenovirus (measured via quantitative PCR) with WSP particles of different sizes were analyzed using a cascade filtration approach using filters with pore sizes of 180 µm, 0.45 µm, and a positively-charged membrane with a pore size of 0.20 µm. Samples were collected from an active WSP system in Michigan, USA consisting of an anaerobic pond, two facultative ponds, and two final storage ponds. F+ coliphage was detected in the first three ponds at quantifiable levels in unfiltered samples and in the filtrate from all filters in the cascade. The differences between the F+ coliphage quantities detected prior to filtration and after the 180-µm filters were negligible and the quantities detected in the filtrate of the 0.45-µm filters were slightly less than half of the quantities detected prior to filtration. The highest quantities of human adenovirus were detected in material retained on the 0.45-µm filters and positivelycharged 0.20-µm membranes in the effluent of the anaerobic pond, indicating associations with particles smaller than 180 µm. While these results provide only a snapshot view of virusparticle associations in WSPs, they do not provide evidence that particle associations cause large differences in the extent of the removal of these viruses in WSPs. The results also do not provide evidence for sedimentation as a major removal mechanism for these viruses.