Somatic coliphage as a promising fecal viral surrogate for wastewater treatment performance evaluation in tropical coastal region

Abstract

Traditional methods using fecal indicator bacteria as water quality metrics do not accurately represent the risks from viral pathogens, which may follow different fate and removal patterns in wastewater treatment processes. Coliphages have been studied as viral surrogates for water quality and have shown improved detection of viral pathogens compared with bacterial indicators, but there is a lack of research on coliphages as viral surrogates in tropical coastal wastewater treatment systems. This study examined the concentration dynamics of somatic and F-specific coliphages in primary influent, secondary effluent, and final effluent from a tropical coastal wastewater treatment plant and compared their concentrations and removal efficiencies against common human viral pathogens, including norovirus GI, norovirus GII, enterovirus, and adenovirus, as well as plant pathogens, including tomato brown rugose fruit virus and pepper mild mottle virus. Somatic coliphages were abundant and exhibited relatively low variability across the treatment train, with a mean cumulative log removal of 4.50 ± 0.67 log₁₀. They also showed strong statistically significant correlations with both human-associated viral pathogens (mean ρ = 0.71 ± 0.10, p < 0.05) and plant-associated viral pathogens (mean ρ = 0.81 ± 0.05, p < 0.05). In contrast, F-specific coliphages occurred at lower abundance, exhibited greater variability, and had a lower cumulative mean log removal (2.55 ± 1.42 log₁₀). While F-specific coliphages were also significantly correlated with human-associated (mean ρ = 0.51 ± 0.07, p < 0.05) and plant-associated viral pathogens (mean ρ = 0.60 ± 0.06, p < 0.05), these correlations were consistently weaker than those observed for somatic coliphages. This study offers new insight into how somatic coliphages may serve as effective viral surrogates in wastewater treatment processes located in tropical coastal regions.