Effect of selected wastewater characteristics on estimation of SARS-CoV-2 viral load in wastewater

<p dir="ltr">Wastewater-based epidemiology has been used as a tool for surveillance of COVID-19 infections. This approach is dependent on the detection and quantification of SARS-CoV-2 <a href="https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/rna" target="_blank">RNA</a> in untreated/raw wastewater. However, the quantification of the <a href="https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/virus-rna" target="_blank">viral RNA</a> could be influenced by the physico-chemical properties of the wastewater. This study presents the first use of Adaptive Neuro-Fuzzy Inference System (ANFIS) to determine the potential impact of physico-chemical characteristics of wastewater on the detection and concentration of SARS-CoV-2 RNA in wastewater. Raw wastewater samples from four <a href="https://www.sciencedirect.com/topics/chemical-engineering/wastewater-treatment-plant" target="_blank">wastewater treatment plants</a> were investigated over four months. The physico-chemical characteristics of the raw wastewater was recorded, and the SARS-CoV-2 RNA concentration determined via amplification with droplet digital <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/polymerase-chain-reaction" target="_blank">polymerase chain reaction</a>. The wastewater characteristics considered were <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/chemical-oxygen-demand" target="_blank">chemical oxygen demand</a>, <a href="https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/flow-rate" target="_blank">flow rate</a>, ammonia, pH, permanganate value, and total solids. The mean SARS-CoV-2 RNA concentrations ranged from 648.1(±514.6) copies/mL to 1441.0(±1977.8) copies/mL. Among the parameters assessed using the ANFIS model, ammonia and pH showed significant association with the concentration of SARS-CoV-2 RNA measured. Increasing ammonia concentration was associated with increasing viral RNA concentration and pH between 7.1 and 7.4 were associated with the highest SARS-CoV-2 concentration. Other parameters, such as total solids, were also observed to influence the viral RNA concentration, however, this observation was not consistent across all the <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/waste-water-treatment-plant" target="_blank">wastewater treatment plants</a>. The results from this study indicate the importance of incorporating wastewater characteristic assessment into wastewater-based epidemiology for a robust and accurate COVID-19 surveillance.</p>