AWWA water science最新文献

The occurrence of per- and polyfluoroalkyl substances (PFAS) in wastewater treatment plants (WWTPs) is well recognized. While several studies have examined the occurrence of PFAS in WWTPs, studies assessing the extent to which unit processes impact PFAS phase distribution are relatively lacking. Herein, PFAS enrichment in foams generated during aeration and PFAS accumulation in solids dewatering streams were evaluated in WWTPs. Results of this screening-level study showed that perfluorooctane sulfonate (PFOS) concentrations were enriched up to three orders of magnitude in foams relative to the aqueous phase. Similarly, total PFAS concentrations in solids dewatering streams were enriched up to 380 times relative to the aqueous influent. The PFAS mass in the dewatering stream was a significant component of the overall PFAS mass exiting the WWTP at one of the facilities examined. Results of this study suggest that there is potential to mitigate PFAS by improved management of these foams and dewatering waste streams.

The ability of a low-power ultrasound system to alter the physiology of cyanobacteria cells in controlled field applications was evaluated. Serratia sp., a model bacteria, and cyanobacteria collected from a bloom containing Microcystis sp. and Aphanizomenon sp., were placed in sound transparent containers and exposed to ultrasound in field studies. No observed changes in Serratia sp. and cyanobacteria gas vesicles between unexposed controls and ultrasound exposed samples were found. Cell viability and phycocyanin concentration for both model bacteria and environmental samples were not significantly affected. At the highest acoustic pressure measured (3.5 kPa), 1 m from the transducer, the acoustic pressures were over 100× lower than gas vesicle critical collapse pressures. Moreover, the ultrasound frequencies emitted are significantly lower than gas vesicle resonance frequencies. Therefore, consistent with pressure and frequency measurements, we found no evidence that gas vesicle collapse is the mechanism of ultrasound as a cyanobacteria mitigation strategy.

Modeling premise plumbing systems requires accurate treatment of fixture-specific pressure and flow rate relationships. Each fixture in a building may experience different flow rates based on variable service pressure, its unique pressure-flow behavior, and demands throughout the building. Unique experimentally derived pressure-flow parameters for four faucets, a shower/tub fixture, and toilet were developed. The Water Network Tool for Resilience (WNTR) was also used to explore the impact of premise plumbing systems on water distribution systems through two simple skeletonization cases. Minimum pressures for nodes in water distribution system models that represent demand aggregated premise plumbing systems will likely be non-zero and must capture additional pressure drop or elevation differences at the building scale and associated components, such as water meters or backflow preventers. Results showed that flow rates are impacted by pressure in these systems in complex ways, and usage and system characteristics must be considered to be modeled accurately.

Spray aeration is a comparatively low-cost option to reduce trihalomethane (THM) concentrations in distribution system storage. The effect of spray aeration on unregulated, toxic disinfection by-products was investigated in a bench-scale apparatus in closed-tank and open-tank experiments. In the closed-tank experiments, initially over 90% of THMs, trichloroacetonitrile, and chloropicrin were removed, while 36% of dihaloacetonitriles were removed. However, due to the buildup of concentrations in the tank headspace, removal rates for all compounds decreased significantly with time, falling to 44% removal of THMs, 76% removal of trichloroacetonitrile, and 58% removal of chloropicrin. Removal of dihaloacetonitriles decreased to zero. In the open-tank experiments, THM removal rates were high and did not decrease with time. Considering the results with open and closed tanks as approximate bounds for performance expected under real-world conditions in storage tanks, the findings suggest that spray aeration may not significantly reduce haloacetonitrile-related toxicity while halonitromethane-related toxicity may be reduced.

Two commonly used methods for cyanotoxin analysis are enzyme-linked immunosorbent assay (ELISA) and liquid chromatography/tandem mass spectrometry (LC–MS/MS). Two rounds of interlaboratory comparisons of ELISA and LC–MS/MS analyses were conducted with 12 participating laboratories to evaluate method performances in various matrices, including cyanobacterial bloom and drinking water samples. Fifteen cyanotoxins, including 12 microcystin variants, nodularin, anatoxin-a, and cylindrospermopsin were evaluated. The impact of sample matrices, preservatives, and quenching reagents was assessed, and no substantial effects were observed. Overall, comparable results were obtained among laboratories performing ELISA and LC–MS/MS analyses, respectively. ELISA results for fortified samples matched more closely with those from LC–MS/MS when microcystin cross-reactivities were considered, providing data 26% closer to theoretical values on average. This study demonstrates that understanding the effect of cross-reactivities when comparing ELISA and LC–MS/MS results and considering potential variabilities in commercial standards is important when interpreting data from these two methods.