Incubation studies were conducted to assess the influence of various combination levels of alkaline (pH 12.2) powerplant fly ash and sewage sludge on soil microbial activity and numbers. A Glynwood (fine, illitic, mesic. Aquic Hapludalf) silt loam soil was mixed with 0, 5, 10, or 20% (w/w) ash and 0 or 5% composted sewage sludge. Respiration was strongly depressed in the 10 and 20% ash treatments over 28 d. Sludge addition improved respiration in all ash treatments except the 20% treatment. Total bacterial, actinomycete, and fungal counts in the soil typically decreased with increasing ash content. Counts were depressed by 57, 80, and 86%, respectively, at the 20% ash application rate. Sludge application increased microbial numbers but all populations were lower at the highest ash rates compared to the untreated control. Soil phosphatase, sulfatase, dehydrogenase, and invertase were inhibited as ash treatment levels increased. Catalase activity was not significantly affected by ash concentration. Addition of the sludge to the ash-soil mixtures generally enhanced enzyme activity. The results indicate that high rates of fly ash to soils may hinder normal decomposition and nutrient cycling processes. This may be partially alleviated, however, by coapplication of a readily oxidizable organic substrate such as sewage sludge.

Drinking water contamination with per-and polyfluoroalkyl substances (PFAS) poses a health risk for communities across the country. The vast majority of the water systems across the United States lack both the technology and the funds to filter out PFAS. Release of PFAS with industrial wastewater from a variety of facilities is a significant contributor to PFAS contamination of drinking water. Here, we provide a screening-level analysis of the potential for environmental PFAS releases from contaminated sites, active industrial sites, wastewater treatment plants, and waste disposal sites (including active and inactive landfills) nationwide. With specific case studies from the US states of Michigan and California, we examine how testing has identified a large number of diverse PFAS sources. Testing results alongside the list of potential sources can be used to inform state-or local-level investigations as well as aid in the development of effluent guidelines and industrial pretreatment programs.