ABSTRACT
Wastewater based epidemiology grew in popularity during the COVID-19 pandemic showing particular utility where individual testing was infeasible due to the cost, lack of testing supplies, non-compliance, and other challenges. Here, a monitoring study was performed across four wastewater collection systems with varying size and design (e.g., two combined sewer systems compared to two separate sanitary sewer systems). Generally, correlations between the previous week’s testing results correlated best with N1 gene copies observed in the sewage. To understand the potential for attenuation and accumulation of SARS-CoV-2 gene copies in sewer biofilms, swabs were collected from select pipes and an annular biofilm reactor was used to simulate the loading and shear in sewer pipes. SARS-CoV-2 was above detection in the simulated sewer biofilm when cases were too low to quantify in the wastewater and accumulated over the second wave of cases in the study region. Results presented here can provide insight into interpretation of wastewater-based epidemiology data. Copyright © 2021 Water Environment Federation
ABSTRACT
Wastewater-based epidemiology is a useful tool to exist for normalizing wastewater virus concentrations to the flow and number of people in the sewershed, less information is available regarding the potential for in-sewer processes to impact these observations. The aim of this research was to evaluate SARSCoV-2 accumulation in simulated sewer biofilms. An annular biofilm reactor was continuously fed with raw wastewater from a separate sanitary sewer during periods of high and low COVID-19 incidence. Periodic biofilm samples were collected, and SARSCoV-2 and pepper mottle virus gene copies were quantified via RT-qPCR. During the period of low COVID-19 incidence, SARSCoV-2 was below detection or below the quantitation limit in the sewer biofilms. During the period of high COVID-19 incidence, SARS-CoV-2 gene copies increased in the sewer biofilm across the 4-week study period. Accumulation of similar to 700 genome copies/cm(2) was observed in the biofilm and correlated with cumulative cases in the county. During both study periods, the pepper mottle virus plateaued after 1 week. These results provide insight into the potential for SARS-CoV-2 retardation in sewer biofilms, which may be of interest for interpreting wastewater-based epidemiology data, protecting utility workers, and monitoring infections.
ABSTRACT
Wastewater surveillance has been used as a tool for COVID-19 outbreak detection particularly where there was not capability in place for routine and robust individual testing. Given clinical reports that earlier detection is possible following infection from throat/nasal samples compared to fecal samples for COVID-19 patients, the utility of wastewater testing where robust individual testing is possible is less clear. The objective of this study was to compare the results of weekly required COVID-19 saliva tests to weekly wastewater monitoring for residential buildings (i.e., dormitories) located across three college campuses capturing wastewater from 80 to 441 occupants per sampling location. Sampling occurred during the spring semester of the 2021 academic year which captured the third wave of SARS-CoV-2 cases in the study region. Comparison of the saliva and wastewater testing results indicated that the wastewater SARS-CoV-2 concentrations had a strong linear correlation with the previous week's percentage of positive saliva test results and a weak linear correlation with the saliva testing results surrounding the wastewater sampling (four days before and 3 days after). Given that no correlation was observed between the wastewater and the saliva testing from the following week, the weekly saliva testing captured spikes in COVID-19 cases earlier than the weekly wastewater sampling. Interestingly, the N1 gene was observed in buildings on all campuses, but N2 was observed in wastewater on only one of the campuses. N1 and N2 were also observed in sewer biofilm. The campus-specific challenges associated with implementation of wastewater surveillance are discussed. Overall, these results can help inform design of surveillance for early detection of SARS-CoV-2 in residential settings thereby informing mitigation strategies to slow or prevent the spread of the virus among residents in congregate living.