Occurrence and fate of potential pathogenic bacteria as revealed by pyrosequencing in a full-scale membrane bioreactor treating restaurant wastewater

Abstract

One of the primary concerns on wastewater reuse is the presence of pathogenic bacteria. Considering that indicator bacteria might only offer limited information, we applied high-throughput pyrosequencing in this study to reveal bacterial pathogen diversity in a full-scale membrane bioreactor (MBR) treating restaurant wastewater. The results showed that fecal indicator bacteria could provide a rough estimation rather than an accurate characterization of the potential pathogenic bacteria in wastewaters, particularly from non-fecal sources. In general, MBR treatment showed good removal of potential pathogenic bacteria. The bacterial count of Arcobacter was decreased by nearly seven orders of magnitude, from (8.35 ± 0.87) × 10⁷ to <10 counts per mL, and Aeromonas, Enterobacter, Enterococcus, and Pseudomonas were not detected in the treated wastewater. The most dominant potential pathogens in activated sludge and treated wastewater were affiliated to the genera of Legionella, Clostridium and Mycobacterium. Species-specific comparison showed that only a small portion (0.0–1.6%) of the corresponding sequences had identities of > 99% to the neighbor pathogenic species, including Arcobacter butzleri and Arcobacter cryaerophilus. This study, therefore, provides insights into the occurrence and fate of potential bacterial pathogens in restaurant wastewater treatment and reclamation using MBRs.