Pepper mild mottle virus as a process indicator at drinking water treatment plants employing coagulation-sedimentation, rapid sand filtration, ozonation, and biological activated carbon treatments in Japan

To assess the potential of pepper mild mottle virus (PMMoV) as a viral process indicator, its reduction through coagulation-sedimentation (CS) and rapid sand filtration (RSF) were compared with those of Escherichia coli, previously used viral indicators, and norovirus genotype II (NoV GII; enteric virus reference pathogen) in a bench-scale experiment. PMMoV log(10) reductions in CS (1.96 +/- 0.30) and RSF (0.26 +/- 0.38) were similar to those of NoV GII (1.86 +/- 0.61 and 0.28 +/- 0.46). PMMoV, the most abundant viruses in the raw water, was also determined during CS, RSF, and advanced treatment processes at two full-scale drinking water treatment plants under strict turbidity management over a 13-month period. PMMoV was concentrated from large-volume water samples (10-614 L) and quantified by Taqman-based quantitative polymerase chain reaction. The PMMoV log(10) reduction in CS (2.38 +/- 0.74, n = 13 and 2.63 +/- 0.76, n = 10 each for Plant A and B) and in ozonation (1.91 +/- 1.18, n = 5, Plant A) greatly contributed to the overall log(10) reduction. Our results suggest that PMMoV can act as a useful treatment process indicator of enteric viruses and can be used to monitor the log(10) reduction of individual treatment processes at drinking water treatment plants due to its high and consistent copy numbers in source water.