Assessment of human adenovirus removal in a full-scale membrane bioreactor treating municipal wastewater

Human adenoviruses (HAdVs) in wastewater samples taken from four different treatment stages of a full-scale municipal wastewater treatment plant (i.e., incoming raw sewage, primary sedimentation effluent, membrane bioreactor (MBR) influent, and MBR effluent) were quantified by real-time PCR assays to further estimate removal efficiency of the HAdVs. Based on hexon gene sequence comparisons, HAdV species A, C, and F were consistently found in the wastewater samples. In general, all three identified HAdV species were detected in most of the wastewater samples using the real-time PCR assays. Overall HAdV concentrations were rather stable over the entire 8-month study period (January-August, 2008) (approximately 10⁶-10⁷ viral particles/L of wastewater for the raw sewage and primary effluent; 10⁸-10⁹ viral particles/L for the MBR influent; and, 10³-10⁴ viral particles/L for the MBR effluent). No significant seasonal differences were noticed for the HAdV abundances. Removal efficiencies of the viral particles in the full-scale MBR process were assessed and showed an average HAdV removal of 5.0 ± 0.6 logs over the study period. The removal efficiencies for F species (average log removal of 6.5 ± 1.3 logs) were typically higher (p-value <0.05) than those of the other two species (average of 4.1 ± 0.9 and 4.6 ± 0.5 logs for species A and C, respectively). These results demonstrate that the full-scale MBR system efficiently removed most HAdV from the wastewater leaving about 10³ viral particles/L in the MBR effluent.