Drinking water distribution system deterioration can affect the water supply and reliability as well as water quality and public health.

During a cyanobacterial harmful algal bloom (HAB) event, drinking water treatment systems face the challenge of balancing acute and chronic health risks by treating the potentially toxin‐producing HAB and simultaneously managing for disinfection byproduct (DBP) formation. To explore the relationship between HAB events and DBP formation, a unique full‐scale study, including paired source water and finished water monitoring, was conducted at five drinking water utilities with HAB‐impacted source waters. Results confirm bench‐scale findings that HAB events in source water contribute to increases in DBP precursors. However, unlike results from laboratory studies, source water HAB‐related parameters and finished water DBPs were not consistently correlated at the five study utilities. These different outcomes suggest regulated DBP formation in utilities with HAB‐impacted source water is complex and influenced by a variety of site‐specific conditions, including source water conditions and data available for operational decision‐making, timing of treatment adjustments, and key operational choices.

While granular activated carbon (GAC) can effectively remove disinfection byproduct (DBP) precursors, its use has raised concerns over the increased formation of some brominated DBP (Br-DBP) species in treated water postchlorination, especially for waters with high bromide concentrations. The Information Collection Rule Treatment Study Database contains the results of the most extensive GAC studies ever conducted nationwide. Data were analyzed to assess the extent of DBP speciation changes and the overall reduction of Br-DBPs by GAC to gain new insights into the bromide effect. Results showed that formation of three brominated trihalomethanes (collectively Br-THM3) varied greatly depending on total organic carbon (TOC) removal and bromide concentrations. Low TOC concentrations in GAC effluents resulted in greatly reduced Br-THM3 formation, except for a few cases where Br-THM3 formation increased. GAC followed by chloramination were likely to better control Br-THM3 formation for waters with high TOC and high bromide. Finally, chlorine demand reduction by GAC was quantified. K E Y W O R D Sbromide, brominated DBPs, GAC, total organic carbon

Spore reduction can be used as a surrogate measure of Cryptosporidium natural filtration efficiency. Estimates of log10 (log) reduction were derived from spore measurements in paired surface and well water samples in Casper Wyoming and Kearney Nebraska. We found that these data were suitable for testing the hypothesis (H) that the average reduction at each site was 2 log or less, using a one-sided Student's t-test. After establishing data quality objectives for the test (expressed as tolerable Type I and Type II error rates), we evaluated the test's performance as a function of the (a) true log reduction, (b) number of paired samples assayed and (c) variance of observed log reductions. We found that 36 paired spore samples are sufficient to achieve the objectives over a wide range of variance, including the variances observed in the two data sets. We also explored the feasibility of using smaller numbers of paired spore samples to supplement bioparticle counts for screening purposes in alluvial aquifers, to differentiate wells with large volume surface water induced recharge from wells with negligible surface water induced recharge. With key assumptions, we propose a normal statistical test of the same hypothesis (H), but with different performance objectives. As few as six paired spore samples appear adequate as a screening metric to supplement bioparticle counts to differentiate wells in alluvial aquifers with large volume surface water induced recharge. For the case when all available information (including failure to reject H based on the limited paired spore data) leads to the conclusion that wells have large surface water induced recharge, we recommend further evaluation using additional paired biweekly spore samples.

Distribution system infrastructure issues can affect water reliability and quality and could contribute to waterborne disease outbreaks. It's important to know potential contamination mechanisms and consider rehab and replacement options.