Investigating the Reduction of Human Adenovirus (HAdV) and Human Polyomavirus (HPyV) in a Sewage Treatment Plant with a Polishing Pond as a Tertiary Treatment

Enteric viruses enter surface waters through discharge of sewage treatment plants. They have a high environmental resistance and persistence and have low infectious doses. The aim of this study was to investigate the efficiency of polishing pond in the removal of viruses and bacteria. The samples were taken approximately once a week at the influent of secondary treatment (n = 39), effluent of secondary treatment (n = 39), and polishing pond (tertiary treatment, n = 29). Human adenoviruses (HAdV) were detected in 82–100 % of wastewater samples, whereas 62–79 % of the samples were positive for human polyomavirus (HPyV). The median concentrations ranged from 6.8 × 103 genome equivalents/l (HAdV) to 6.0 × 103 genome equivalents/l (HPyV). The concentration of HAdV and HPyV did not change significantly during the wastewater treatment. For somatic coliphages and bacteria an overall reduction of 1.84–2.65 log10 has been detected. Based on the data collected, this type of tertiary treatment achieved a significant reduction in bacteria and phages, but not for viruses.