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.