Assessment of Concentration, Recovery, and Normalization of SARS-CoV-2 RNA from Two Wastewater Treatment Plants in Texas and Correlation with COVID-19 Cases in the Community

Abstract

The purpose of this study was to conduct a correlative assessment of SARS-CoV-2 RNA concentrations in wastewater with COVID-19 cases and a systematic evaluation of the effect of using different virus concentration methods and recovery and normalization approaches. We measured SARS-CoV-2 RNA concentrations at two different wastewater treatment plants (WWTPs) in the Bexar County of Texas from October 2020 to May 2021 (32 weeks) using reverse transcription droplet digital PCR (RT-ddPCR). We evaluated three different adsorption–extraction (AE) based virus concentration methods (acidification, addition of MgCl 2 , or without any pretreatment) using bovine coronavirus (BCoV) as surrogate virus and observed that the direct AE method showed the highest mean recovery. COVID-19 cases were correlated significantly with SARS-CoV-2 N1 concentrations in Salitrillo (ρ = 0.75, p < 0.001) and Martinez II (ρ = 0.68, p < 0.001) WWTPs, but normalizing to a spiked recovery control (BCoV) or a fecal marker (HF183) reduced correlations for both treatment plants. The results generated in this 32-week monitoring study will enable researchers to prioritize the virus recovery method and subsequent correlation studies for wastewater surveillance.

Wastewater-based surveillance of COVID-19 and removal of SARS-CoV-2 RNA across a major wastewater treatment plant in San Antonio, Texas

“…45,46 Wastewater samples collected during the third wave of COVID-19 cases (July–August 2021) showed relatively higher SARS-CoV-2 RNA concentrations as compared to other periods in the study area. 35,38 Notably, the SARS-COV-2 RNA levels were relatively lower from April–June 2021 and September–November 2021, which corresponded well with the initiation of vaccination in the study area and the decline in daily incident COVID-19 cases after the third wave, respectively. 34…”

“…The results of the current study are consistent with those of previous studies which indicated that the SARS-CoV-2 N1 assay is more sensitive than the N2 assay and both are highly correlated. 35,43,44 During the rst three months of our study period, the average concentrations of both N1 and N2 gene targets were below 5000 copies per L. However, the trend in viral loads started to increase on July 5th and reached its peak on August 2nd, 2021, where the SARS-CoV-2 N1 and N2 concentrations in inuent samples were 2.8 × 10 4 copies per L and 5.2 × 10 3 copies per L, respectively.…”

“…The SARS-CoV-2 virus in the wastewater samples was concentrated using an adsorption-extraction method combined with high-speed centrifugation as described in previous studies. [35][36][37] To determine the recovery efficiency of the virus concentration and nucleic acid extraction methods applied in this study, an attenuated vaccine strain of bovine coronavirus (Calf-Guard, Zoetis, Parsippany, NJ) was used as a surrogate viral RNA target. Prior to the sample concentration process, wastewater samples were directly spiked with 10 6 copies of bovine coronavirus (BCoV) per liter of wastewater.…”

Community-Based SARS-CoV-2 Testing Using Saliva or Nasopharyngeal Swabs to Compare the Performance of Weekly COVID-19 Screening to Wastewater SARS-CoV-2 Signals

“…Recently, a significant number of studies have been published that improve confidence in the ability of WBE to assess SARS-CoV-2 transmission in the community. − The topics addressed by these studies range from assessment and normalization of SARS-CoV-2 RNA in wastewater to a better understanding of the relationship between RNA load and COVID-19 clinical cases and hospitalization. The unique feature of our study is the evaluation of the relationship between wastewater RNA load and COVID-19 in an underserved community and the importance of elevating visibility of these communities to public health authorities.…”

Temporal Variation of SARS-CoV-2 Levels in Wastewater from a Meat Processing Plant

“…Most WBS studies for COVID-19 focused on analyzing and monitoring wastewater samples taken from wastewater treatment plants (WWTPs) or hospitals [ 1 , 2 , 3 , 4 ]. Several studies showed a correlation between SARS-CoV-2 levels in wastewater and positive COVID-19 cases reported from clinic testing or public records, suggesting that wastewater-based monitoring can provide information for large-scale dynamic of the pandemic [ 5 , 6 , 7 , 8 , 9 ]. Although it is important to investigate the COVID-19 prevalence and dynamic in communities and cities scales, with the negative economic impact of the COVID-19 around the world, the interests of business owners lay in the presence of the viruses and infected individuals in the local facility, which is crucial for updating the control procedures in a timely manner to respond to the decreasing or rising risks and ensuring the safety of the workers during the business recovery stage [ 10 , 11 , 12 ].…”