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Session 01B: Risk Assessment/Stormwater - Livestream
1:15pm - 2:00pm
Boise’s SARS-CoV-2 Wastewater Dataset and the Future of PCR Testing at WRFs
Viewing wastewater as a resource opened pathways of innovation previously unforeseen. The SARS-CoV-2 pandemic amplified a similar paradigm of innovation in the science of Wastewater-Based Epidemiology (WBE). In May of 2020, the City of Boise began sampling wastewater at both of its Water Renewal Facilities (WRFs) to test for SARS-CoV-2 virus using quantitative polymerase chain reaction (qPCR). On June 17th the City began daily sampling and continued through two infection peaks. The City’s dataset is one of the most robust datasets in the country for WBE.
RT-qPCR quantifies copies of virus RNA in the wastewater matrix. The City contracted with the University of Missouri to perform qPCR. Virus quantities in the wastewater ranged from 50,000 to 1,395,000 copies per liter. Puro virus recovery was used as a proxy indicator of the relative amount of virus recovered through the qPCR method and ranged widely from 2 to 82 percent, with an average of 11 percent. Genetic sequencing was also used to perform early screening to detect if SARS-CoV-2 variants were present.
Visualizations of the data show clear correlation with number of confirmed cases in Ada County. Numerical correlations were weak because of daily variability, however the visual correlation revealed that during periods of infection rate increases the wastewater signal provided four to seven days advanced notice prior to case report date. The City coordinated with Centers for Disease Control, Central District Health, and St. Luke’s Hospital to maximize the benefit of WBE.
Laboratory layouts and equipment specifications were evaluated for conducting qPCR molecular testing at WRF lab facilities. Experience designing 26 public health labs in the United States was leveraged to customize the “unidirectional flow of sample” design approach within the WRF laboratory context.
Using qPCR at WRFs will continue to expand the paradigm of wastewater as a resource. The current application of qPCR for SARS-CoV-2 testing reveals that indicator virus testing for disinfection (such as adenovirus and norovirus), identification of specific organisms for biological nutrient removal within WRFs, and early detection of future diseases in wastewater are destined to become integral parts of ongoing WRF operations in the modern era.
2:00pm - 2:45pm
Beavers Improve Water Quality in an Urban Watershed
City of Gresham, Oregon, United States of America; email@example.com
Beaver populations have been returning to urban watersheds in the Pacific Northwest, bringing with them both benefits and challenges. To better understand the effects on local watersheds, we conducted several studies of beaver activities within the city of Gresham, Oregon. We looked at pollutant removal efficiencies in a large stormwater treatment wetland with and without beaver activity, assessed the effect of beaver dams on stream temperatures, and documented the physical and biological changes to stream channels near dams. We found that pollutants of concern were generally removed more efficiently when beaver dams were present in the treatment wetlands. This is likely due to the water being filtered through the dams which are repaired after each storm. The effects of dams on stream temperatures varied depending on site characteristics, but all dams created ponds with temperature heterogeneity and stratification. Dams on higher order streams sometimes reduced overall stream temperature by pulling water from the entire stratified water column and increasing hyporheic flow. Within just a few years of beaver activity, several sites experienced increased stream complexity with new gravel bars, side channels, and braided streams. We also found increased macroinvertebrate diversity in the relatively sediment-free cobbles downstream of dams. These findings demonstrate multiple benefits of beavers in urban watersheds. After communicating these benefits to stakeholders, we have been working with beaver experts to adapt our systems to find ways to protect infrastructure while coexisting with beavers through targeted use of technologies such as pond levelers, culvert fencing, and tree protection.