Longitudinal monitoring of SARS-CoV-2 in wastewater using viral genetic markers and the estimation of unconfirmed COVID-19 cases.

In this study, wastewater-based surveillance was carried out to establish the correlation between SARS-CoV-2 viral RNA concentrations in wastewater and the incidence of corona virus disease 2019 (COVID-19) from clinical testing. The influent wastewater of three major water reclamation facilities (WRFs) in Northern Nevada, serving a population of 390,750, was monitored for SARS-CoV-2 viral RNA gene markers, N1 and N2, from June 2020 through September 2021. A total of 614 samples were collected and analyzed. The SARS-CoV-2 concentrations in wastewater were observed to peak twice during the study period. A moderate correlation trend between coronavirus disease 2019 (COVID-19) incidence data from clinical testing and SARS-CoV-2 viral RNA concentrations in wastewater was observed (Spearman r = 0.533). This correlation improved when using weekly average SARS-CoV-2 marker concentrations of wastewater and clinical case data (Spearman r = 0.790), presumably by mitigating the inherent variability of the environmental dataset and the effects of clinical testing artifacts (e.g., reporting lags). The research also demonstrated the value of wastewater-based surveillance as an early warning signal for early detection of trends in COVID-19 incidence. This was accomplished by identifying that the reported clinical cases had a stronger correlation to SARS-CoV-2 wastewater monitoring data when they were estimated to lag 7-days behind the wastewater data. The results aided local decision makers in developing strategies to manage COVID-19 in the region and provide a framework for how wastewater-based surveillance can be applied across localities to enhance the public health monitoring of the ongoing pandemic.

Investigation of direct waste-activated sludge dewatering benefits and costs in a water resource recovery facility.

Dewatering of anaerobic digested (AD) sludge containing waste-activated sludge (WAS) from enhanced biological phosphorus removal (EBPR) poses numerous challenges including poor dewaterability, struvite scale formation, and recycling of high N and P levels in the sludge liquor to the treatment process. A full-scale water reclamation facility was investigated to mitigate these problems by experimenting with direct dewatering of EBPR WAS, bypassing the AD step. The investigations experimented with various blends of AD primary sludge with undigested thickened WAS to achieve dewatering performance improvements and overall operational cost savings. Direct thickened WAS dewatering has had many positive impacts including enhanced sludge cake solids concentration, reduced chemical use for facility operations, reduced struvite scaling, reduced biogas conditioning media servicing, eliminated need for centrate treatment, recovered capacity of existing unit operations including anaerobic digesters, and eliminated several proposed capital improvement projects that were previously deemed necessary. Although bypassing of WAS to AD reduced total biogas production, the specific gas yield increased to meet all of the facility's biogas demands and minimized excess gas flaring. The overall biosolids production mass increased causing increased transportation costs for disposal and caused notable odors, both of which are being currently investigated. PRACTITIONER POINTS: Direct WAS dewatering bypassing anaerobic digestion yields operational and process benefits in an EBPR water resource recovery facility Dewatered cake solids were increased compared with combined primary and WAS anaerobic digestion and dewatering Nutrient loads in sludge processing returns streams and operational costs are reduced by direct WAS dewatering.

Full-scale N removal from centrate using a sidestream process with a mainstream carbon source.

An innovative approach to treat centrate for rapid nitrogen load discharge reduction was investigated and applied at the Truckee Meadows Water Reclamation Facility (TMWRF) in Reno, NV. This process allowed TMWRF to circumvent an anticipated exceedance of the individual waste load allocation in 2018. Existing infrastructure and equipment were re-purposed in a full-scale suspended growth biological centrate treatment system, attaining simultaneous nitrification, and denitrification with no additional capital investment. Functioning within a few days of start-up, the average ammonia reduction was 81% (1,106 kg/day) and the average total nitrogen reduction in the sidestream was 53% (757 kg/day) using primary effluent as carbon source. Alkalinity and carbon limitations were both anticipated and observed; however, adaptive operations allowed for balancing of nitrification and denitrification processes, providing pH stability and success in meeting treatment goals. Immediately after the sidestream treatment system was placed into service, nitrogen in the mainstream facility was measured at concentrations significantly lower than typical and was sustained at historically low concentrations throughout the operation. This translated into a significant methanol cost savings of $1,500 per day (USD). The system has become a critical supplemental treatment process during upcoming rehabilitation projects to address aging infrastructure of existing nitrogen treatment facilities. PRACTITIONER POINTS: Full scale demonstration of sidestream N removal using a hybrid process. Integration of the sidestream N process to reduce N effluent load without alkalinity or supplementary carbon augmentation. Operational solution to reduce operating costs without new infrastructure.