2014 Volume 12 Issue 3 Pages 221-230
Viruses hosted by microorganisms in activated sludge are of particular interest for researchers because they may affect the performance of wastewater treatment. In this study, the authors investigated at which condition of wastewater treatment viruses, especially double stranded DNA (dsDNA) viruses, were released from activated sludge to the supernatant. To determine the concentrations of viruses, supernatant samples were filtered through membrane filter, viral capsid was digested by treatment with proteinase K, and the dsDNA concentration was determined. The authors confirmed that most of dsDNA in the filtered supernatant cannot be digested by DNase I, and thus treatment with DNase I was omitted. The behavior of dsDNA viruses was monitored in twelve selected cycles from three laboratory-scale sequencing batch activated sludge reactors with sequencing anaerobic and aerobic conditions. The concentrations of dsDNA viruses increased at different timings of treatment: during anaerobic phase, aerobic phase, and settling phase. The rate of increase was varied, sometimes rapid while other times gradual. Decrease of dsDNA concentration was also observed. The behavior of dsDNA viruses in activated sludge during wastewater treatment was found to be very diverse and complex.