Effective strategies for pathogen reduction in decentralized wastewater treatment systems

Decentralized wastewater treatment using membrane bioreactors (MBRs) is a suitable alternative for the removal of pathogens, including bacteria and viruses, thus reducing the risk of infectious disease outbreaks. In this research, the effectiveness of different MBRs in removing pathogenic bacteria with clinical relevance (Klebsiella spp. and Enterococcus spp.) and enteric viruses (Norovirus - NoV - genogroups GI and GII, Sapovirus - SaV - and Hepatitis E Virus -HEV-) was evaluated in two decentralized collection systems: Demosite 1 (urban wastewater separated in black and grey fractions) and Demosite 2 (hospital effluents). We also evaluated the applicability of pepper mild mottle virus (PMMoV) as general fecal contamination biomarker in water samples and its potential as indicator of viral removal in the two decentralized systems. Our data demonstrated that decentralized treatment through anaerobic and combined anoxic/aerobic treatment methods at both demosites efficiently eliminated pathogenic bacteria and enteric viruses. Log Removal Values (LRVs) at Demosite 1 and Demosite 2 reached up to >4.98 and > 4.95 for bacteria, respectively, and >7.53 and > >6.78 for enteric viruses, respectively. Enterococcus spp. such as E. faecalis and E. hirae, and NoV (GII and a lesser extent GI) were the most recalcitrant pathogens in the systems. We also demonstrated the potential of PMMoV as an indicator of enteric viral reduction during decentralized treatment process. This work highlights the reliability of decentralized treatment systems in reducing pathogenic microorganisms, offering a practical solution for improving public health and environmental safety.