Viral Contaminants in a Philippine Wastewater Treatment Plant: Quantification and Treatment Reduction.

In the Philippines, most of the population relies on decentralized wastewater systems, particularly septic tanks, and the rest on centralized wastewater systems. However, the performance of wastewater treatment systems in the Philippines in reducing viral contaminants remains to be characterized; thus, in this study, the occurrence and reduction of viruses in wastewater before and after treatment were assessed at a wastewater treatment plant (WWTP) that utilizes biological treatment technologies in the Philippines. Influent (n = 18) and effluent (n = 18) samples collected from WWTP from April to August 2024 were centrifuged, followed by viral nucleic acid extraction. Cross-assembly phage (crAssphage) was quantified through quantitative polymerase chain reaction (qPCR), and pepper mild mottle virus (PMMoV), influenza A virus (Inf-A), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and norovirus genogroups I (NoV-GI) and II (NoV-GII) were quantified by reverse transcription-qPCR. All viral targets were quantified in wastewater before and after treatment, except for Inf-A and SARS-CoV-2, which were absent in all effluent samples. The reduction in viral loads in wastewater after treatment was determined, with crAssphage, PMMoV, NoV-GI, and NoV-GII showing high log10 reduction values (LRVs) of 4.35, 4.28, 4.56, and 4.00, respectively, while their lowest LRVs were 2.17, 0.38, 0.72, and − 0.99, respectively. The persistence of crAssphage and PMMoV in wastewater samples and their significant positive associations with NoV-GI and NoV-GII suggest their potential application as indicators of enteric viruses in Philippine wastewater. These findings highlight the importance of viruses in characterizing treatment plant reduction performance and water and wastewater quality in the Philippines.