Comparative enteric viruses and coliphage removal during wastewater treatment processes in a sub-tropical environment

Microbiological safety of reclaimed water is one of the most important issues in managing potential health risks related to wastewater recycling. Presence and removal of human adenovirus (HAdV), human polyomavirus (HPyV), human torque teno virus (HTtV) and somatic coliphage family Microviridae in three wastewater treatment plants (WWTP) in sub-tropical Brisbane, Australia was investigated. All three WWTPs employ activated sludge process with added on Bardenpho process for nutrient removal. HPyV, HAdV, HTtV and Microviridae were consistently detected in the influent (10⁵ to 10⁶ Genomic copies (GC) L^-1) and secondary treated effluent (10² to 10³GCL^-1). The results of this study suggest that, under appropriate conditions, WWTPs with activated sludge process in sub-tropical climate could be an effective treatment barrier with >3 log₁₀ removal of enteric virus. The geometric mean of pooled data for each virus from all sites showed the highest removal for HPyV (3.65 log₁₀) and lowest for HAdV (2.79 log₁₀) which was statistically significant (p=0.00001). Whereas, the removal rate of HTtV and Microviridae was identical (2.81 log₁₀). A poor correlation between the presence of enteric virus in influent or effluent with routinely monitored physicochemical parameters suggests limited use of physicochemical parameters as predictors of enteric virus presence. High prevalence of HAdV in influent and effluent combined with comparatively low removal suggest that it could be used as a model microorganism for determining enteric virus removal efficacy. Additional tertiary treatment may be required prior to effluent reuse for non-potable purposes or discharge into the recreational waters to prevent exposure of people to health hazards.