Year-long wastewater monitoring for SARS-CoV-2 signals in combined and separate sanitary sewers

Predicting wastewater treatment plant influent in mixed, separate, and combined sewers using nearby surface water discharge for better wastewater-based epidemiology sampling design

For wastewater sample collection approaches supporting public health applications, few high hydrologic activity normalizing guidelines currently consider readily available environmental flow data that may earlier capture information regarding periods of influent mixing and dilution of wastewater with groundwater and runoff. This study aimed to identify wastewater sampling rules for high hydrological activity events, allowing for an earlier decision point in the control of dilution before sample collection. We defined the sampling rules via data-driven models (Random Forest and linear regression) using environmental data (i.e., wastewater treatment facility influent rates, nearby stream discharge flow, and precipitation). These models were applied to five treatment plants in Jefferson County, Kentucky (USA) in mixed, separate, and combined sewers with different population sizes. We proposed cutoffs of 10 %, 25 %, and 50 % flow conditions for orientation towards public health samples. The results showed a strong nonlinear relationship between nearby stream discharge and treatment facility flow rates, which was used to infer the hydrological conditions that produce high volumes of diluted wastewater in the sewer system. Accumulated Local Effects and SHapley Additive exPlanations aided in deciphering the relationship between the predictors and response variables of the Random Forest models. The influent rate to the treatment plant from the previous day and two USGS stream gages were needed to adequately predict the degree of infiltration and inflow mixing on a given day. Surface water discharge data can be used to provide an earlier workflow decision point during wet weather periods to improve understanding of flow conditions for wastewater-based epidemiological studies to inform laboratory analysis and data interpretation. Not only total flow, but also the specific proportions of infiltration and inflow to wastewater volume in influent should be considered when analyzing data for normalization purposes, and our method provides a starting point for doing so rapidly and at low cost.

Wastewater surveillance of SARS-CoV-2 at intra-city level demonstrated high resolution in tracking COVID-19 and calibration using chemical indicators

Wastewater-based epidemiology has proven to be a supportive tool to better comprehend the dynamics of the COVID-19 pandemic. As the disease moves into endemic stage, the surveillance at wastewater sub-catchments such as pump station and manholes is providing a novel mechanism to examine the reemergence and to take measures that can prevent the spread. However, there is still a lack of understanding when it comes to wastewater-based epidemiology implementation at the smaller intra-city level for better granularity in data, and dilution effect of rain precipitation at pump stations. For this study, grab samples were collected from six areas of Seattle between March-October 2021. These sampling sites comprised five manholes and one pump station with population ranging from 2580 to 39,502 per manhole/pump station. The wastewater samples were analyzed for SARS-CoV-2 RNA concentrations, and we also obtained the daily COVID-19 cases (from individual clinical testing) for each corresponding sewershed, which ranged from 1 to 12 and the daily incidence varied between 3 and 64 per 100,000 of population. Rain precipitation lowered viral RNA levels and sensitivity of viral detection but wastewater total ammonia (NH₄⁺-N) and phosphate (PO₄^3--P) were shown as potential chemical indicators to calibrate/level out the dilution effect. These chemicals showed the potential in improving the wastewater surveillance capacity of COVID-19.

Monitoring hospital effluents through physico-chemical characterization and genotoxic testing

Inefficient monitoring of the water resource recovery facility at various health care establishments may lead to detrimental effects on human population, especially when such water get mixed with potable municipal water supply. To ensure the efficiency and proper functioning of the water resource recovery facility and quality of water, before it being disposed of, the present study was conducted with the assessment of physico-chemical parameters of water and its genotoxic and cytogenetic effects in mice. The sample water was given ad libitum to animals for three different time durations, that is, 7, 15, and 30 days. Bone marrow chromosomal aberration and bone marrow micronucleus (MN) assay were performed to get the extent of genotoxicity and cytogenicity. The results showed presence of chromosomal aberrations like fragments breaks and ring formation in different groups. Besides this, a significant (p < 0.05*, p < 0.01**, p < 0.001***) decrease in the mitotic index was noted in the group which was given 100% concentrated sample water for 30 days. A significant (p < 0.05*, p < 0.01**, p < 0.001***) increase in MN induction and decreased ratio of polychromatic to normochromatic erythrocytes were observed in groups which were given samples at 10% and 100% concentrations for longer durations. The findings suggest that even the recovered sample water reflects a positive in vivo genotoxic potential when given for a longer duration of 30 days, indicating some lacuna in the treatment process.