SARS-CoV-2 adsorption on suspended solids along a sewerage network: mathematical model formulation, sensitivity analysis, and parametric study

Abstract

Accounting for SARS-CoV-2 adsorption on solids suspended in wastewater is a necessary step towards the reliable estimation of virus shedding rate in a sewerage system, based on measurements performed at a terminal collection station, i.e., at the entrance of a wastewater treatment plant. This concept is extended herein to include several measurement stations across a city to enable the estimation of spatial distribution of virus shedding rate. This study presents a pioneer general model describing the most relevant physicochemical phenomena with a special effort to reduce the complicated algebra. This is performed both in the topology regime, introducing a discrete-continuous approach, and in the domain of independent variables, introducing a monodisperse moment method to reduce the dimensionality of the resulting population balance equations. The resulting simplified model consists of a large system of ordinary differential equations. A sensitivity analysis is performed with respect to some key parameters for a single pipe topology. Specific numerical techniques are employed for the integration of the model. Finally, a parametric case study for an indicative—yet realistic—sewerage piping system is performed to show how the model is applied to SARS-CoV-2 adsorption on wastewater solids in the presence of other competing species. This is the first model of this kind appearing in scientific literature and a first step towards setting up an inverse problem to assess the spatial distribution of virus shedding rate based on its concentration in wastewater.

Optimal Selection of Sampling Points for Detecting SARS-CoV-2 RNA in Sewer System Using NSGA-II Algorithm

“…Petala et al [15] examine the effect of environmental parameters on the adsorption of a virus onto suspended solids and found the ratio of the specific absorption (UV254/DOC) over the dissolved oxygen (DO) to be the parameter with the highest correlation with the viral copies. Kostoglou et al [36] developed a general model for the absorption of SARS-CoV-2 parts on solid particles suspended in wastewater into a sewer system. Hart et al [37] estimated the decay rate of several biomarkers into sewer systems, based on wastewater temperature, and examined the effect of seasonality and travel time on the SARS-CoV-2 loads available for observation at downstream monitoring locations [38].…”

Wastewater monitoring using a novel, cost-effective PCR-based method that rapidly captures the transition patterns of SARS-CoV-2 variant prevalence (from Delta to Omicron) in the absence of conventional surveillance evidence

“…Hence, a methodology has been introduced which rationalizes virus shedding rate data in wastewater with regards physicochemical parameters of wastewater to cope with virus loss by adsorption to sewage suspended particles [20]. The presence of chemical and biological species in wastewater that compete with virus particles in occupying adsorption sites on suspended solids along with topological complications of large scale sewage networks have been considered in a separate publication to assess the spatial distribution of virus shedding rate along the wastewater piping system of a city [21]. In addition, contrary to earlier simplistic statistical approaches, a rigorous model has been proposed to estimate the number of infected people from the viral load in wastewater based on detailed population balances of infected people dynamics and shedding rate variability during disease days [15].…”