Untreated wastewater samples were collected from the Great Lakes Water Authority (GLWA) Water Resource Recovery Facility (WRRF) located in southeast Michigan between April 8 and May 26, 2020. The WRRF is the largest single-site wastewater treatment facility in the US, and it receives wastewater from its service area via three main interceptors: Detroit River Interceptor (DRI), North Interceptor-East Arm (NI-EA), and Oakwood-Northwest-Wayne County Interceptor (O-NWI). A total of 54 untreated wastewater samples were collected (18 per interceptor) at the point of intake into the WRRF. Viruses were isolated from wastewater using electropositive NanoCeram column filters (Argonide, Sanford, Florida). For each sample, an average of 45 L of wastewater was passed through NanoCeram electropositive cartridge filters at a rate of no more than 11.3 L=m. Viruses were eluted and concentrated and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) concentrations were quantified with reverse transcription quantitative polymerase chain reaction (RT-qPCR). SARS-CoV-2 was detected in 100% of samples, and measured concentrations were in the range of 10 4-10 5 genomic copies/L. Quantification of concentrations of human viruses, such as SARS-CoV-2, in wastewater is a critical first step in the development of wastewater-based epidemiology predictive methods. However, accurate prediction involves the incorporation of multiple other measurements, data, and processes, such as the estimation of fate and detention times of viruses in the sewer collection network, estimation of contributing population, incorporation of disease characteristics based on anthropometric data, and others. A viral disease prediction model (Viral PD) that incorporates all these other inputs is currently being developed for COVID-19 in Detroit, Michigan.

The rate of mercury methylation in anoxic wetland sediments is affected by the concentration of bioavailable complexes between Hg and sulfide. Previous research with pure bacterial cultures has shown that addition of ferrous iron reduces the net rate of mercury methylation by decreasing the concentration of dissolved sulfide. To assess the possibility of using this approach to decrease net mercury methylation in restored and constructed wetlands, laboratory experiments were conducted by adding Hg(II) and Fe(II) to sediments collected from six sites in five estuarine wetlands. Addition of 30 mM (0.07 mmol g(-1) or 3.9 mg g(-1)) Fe(II) decreased net mercury methylation relative to that of unamended controls by a factor of 2.1-6.6. In all cases, the observed decrease in net mercury methylation was accompanied by a decrease in the concentrations of sulfide and filterable mercury in the water overlying the sediments. When iron was added to one of the sediment samples at doses that were small relative to the concentration of sulfide present, net mercury methylation either increased slightly or was unaffected. Comparison of the results to speciation model predictions suggests that dissolved reduced sulfur-containing species play a role in the formation of uncharged, bioavailable Hg complexes. Although further research is needed to determine the long-term effect of iron amendment, these results suggest that iron addition decreases mercury methylation in authentic wetland sediments.

Although one potential drawback of wetland construction and restoration is the formation of monomethylmercury, it may be possible to decrease net mercury methylation with the use of an appropriate sediment amendment. Using pure cultures of the sulfate-reducing bacterium Desulfobulbus propionicus (1pr3), we tested the hypothesis that adding ferrous iron to sulfidic wetland sediments decreases mercury solubility and bioavailability and, therefore, net methylation. In sediment-free cultures, net mercury methylation decreased with increasing [Fe(II)]. After 72 h of incubation, more than four times as much net methylmercury formed in the lowest ([Fe(II)] = 10(-6) M) treatment (180 +/- 33 pM) as compared with the highest ([Fe(II)] = 10(-2) M) treatment (42 +/- 14 pM). In cultures containing a model wetland sediment, more than three times as much methylmercury was observed in 10(-6) M Fe(II) treatments (1,010 +/- 95 pM) as compared with treatments amended with 10(-2) M Fe(II) (300 +/- 46 pM). Initial filterable mercury measurements and chemical equilibrium speciation predictions suggest that the lower net methylmercury production in the high-iron treatments was due to a decrease in sulfide activity and a concomitant decrease in the concentration of dissolved mercury. Although iron amendments could potentially minimize net mercury methylation in engineered wetland sediments, further research under field conditions is required to assess the efficacy of this approach.

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