In-sewer biofilm and sediment-derived suspended solids accelerate virus genome-signal decay and implications for...

Mechanistic models in wastewater-based epidemiology rely on robust in-sewer virus genome-signal decay parameters, yet most existing decay estimates are derived from bulk wastewater and neglect the role of suspended solids originating from sewer infrastructure. Here, we quantified the decay of an enveloped virus (porcine epidemic diarrhea virus, PEDV), an enveloped bacteriophage (Phi6), and a non-enveloped bacteriophage (T7) in suspended solids derived from sewer biofilms (BF-SS) and sediments (SD-SS), and compared them with raw wastewater (WW) across temperatures from 4 to 35 °C. Biofilm- and sediment-derived suspended solids significantly accelerated virus genome-signal decay relative to raw wastewater, contributing 34.32-44.15 % and 27.98-41.75 % of the total decay, respectively, under the tested solids conditions and controlled matrix preparation. Elevated temperatures increased decay rates by approximately 2-3 times across all matrices. Integrating these kinetics, we developed a temperature-dependent comprehensive decay model (T-CMD) that jointly represents virus genome-signal decay in wastewater, biofilm-derived, and sediment-derived suspended solids. The T-CMD exhibited 2.2-3.0-fold higher temperature sensitivity compared with wastewater-only models, indicating that neglecting suspended solids leads to systematic underestimation of in-sewer virus genome-signal loss. These findings identify biofilm and sediment-sourced suspended solids as major drivers of virus genome-signal decay in sewers and provide a mechanistic framework to refine sewer process models and improve the accuracy of wastewater-based epidemiology for public health surveillance.