Water Distribution System Failure Risks with Increasing Temperatures.

In the coming decades, ambient temperature increase from climate change threatens to reduce not only the availability of water but also the operational reliability of engineered water systems. Relatively little is known about how temperature stress can increasingly cause hardware components to fail, quality to be affected, and service outages to occur. Changes to the estimated-time-to-failure of major water system hardware and the probability of quality noncompliance were estimated for a modern potable water system that experiences hot summer temperatures, similar to Phoenix, AZ, and Las Vegas, NV. A fault tree model was developed to estimate the probability that consequential service outages in quantity and quality will occur. Component failures are projected to have a percent increase of 10-101% in scenarios where peak summer temperature has increased from 36 to 44 °C, which create the conditions for service outages to have a percent increase of 7-91%. Increased service outages due to multiple pumping unit failures and water quality noncompliances are the most notable concerns for water utilities. The most effective strategies to prevent temperature-related failures should focus on monitoring and correcting chlorine residual and disinfection byproduct concentration, and on cooling pumping unit motors and electronics.

Coupling Bioflocculation of Dehalococcoides mccartyi to High-Rate Reductive Dehalogenation of Chlorinated Ethenes.

Continuous bioreactors operated at low hydraulic retention times have rarely been explored for reductive dehalogenation of chlorinated ethenes. The inability to consistently develop such bioreactors affects the way growth approaches for Dehalococcoides mccartyi bioaugmentation cultures are envisioned. It also affects interpretation of results from in situ continuous treatment processes. We report bioreactor performance and dehalogenation kinetics of a D. mccartyi-containing consortium in an upflow bioreactor. When fed synthetic groundwater at 11-3.6 h HRT, the upflow bioreactor removed >99.7% of the influent trichloroethene (1.5-2.8 mM) and produced ethene as the main product. A trichloroethene removal rate of 98.51 ± 0.05 me- equiv L-1 d-1 was achieved at 3.6 h HRT. D. mccartyi cell densities were 1013 and 1012 16S rRNA gene copies L-1 in the bioflocs and planktonic culture, respectively. When challenged with a feed of natural groundwater containing various competing electron acceptors and 0.3-0.4 mM trichloroethene, trichloroethene removal was sustained at >99.6%. Electron micrographs revealed that D. mccartyi were abundant within the bioflocs, not only in multispecies structures, but also as self-aggregated microcolonies. This study provides fundamental evidence toward the feasibility of upflow bioreactors containing D. mccartyi as high-density culture production tools or as a high-rate, real-time remediation biotechnology.