Secondary disinfection practices of water utilities, particularly the use of chloramines, are at the center of several national drinking water policy discussions. As a response to this ongoing dialogue, AWWA commissioned the Secondary Disinfection Practices Survey – a web‐based survey of water utilities – to determine the percentage of utilities currently using chloramines and those intending to convert to the use of chloramines in the future. Results of the survey indicate 68% of utilities currently use chlorine for secondary disinfection, 29% use chloramines, and 3% use no secondary disinfectant. The results of this survey serve to inform national drinking water policy discussions (i.e., the Stage 2 Disinfectants/Disinfection Byproducts Rule) and to support the continued increase in the use of chloramines.

A review of 35 outbreaks of cryptosporidiosis points to recommendations for prevention of waterborne outbreaks and uncovers a need for more adequate epidemiological data. Cryptosporidium parvum infection occurs worldwide in urban and rural populations, and waterborne outbreaks have been associated with consumption of contaminated drinking water and water during recreational activities. This article reviews the epidemiology and causes of waterborne outbreaks that have been reported in North America and the United Kingdom. Outbreaks were associated with filtered and unfiltered surface water sources, groundwater sources, and contamination of the distribution system. In most outbreaks, sources of contamination and deficiencies in treatment and operation were identified. Available epidemiological information is inadequate to estimate endemic waterborne risks, and analytical studies should be conducted to assess these risks. A major issue to consider in assessing waterborne cryptosporidiosis risks is the role of protective immunity, which may be acquired through low‐level sporadic exposures to C. parvum in drinking water.

Results from two AWWA-sponsored surveys regarding characteristics of drinking water service lines in US community water systems (CWSs) are described. For a detailed review of regulatory and water chemistry characteristics of lead in drinking water, see Brown and Cornwell (2015), Brown et al. (2015, 2013), Schock and Lytle (2011), and Schock (1989), and the many related references found within these papers. PREVIOUS NATIONAL LEAD SERVICE LINE ESTIMATES AWWA conducted a similar survey in 1988, summarized by the US Environmental Protection Agency (USEPA) (1991), Weston and EES (1990), and Frey (1989). The first two references present national lead service line (LSL) estimates. USEPA (1991) reported that the methodology in the initial AWWA survey estimated 7.0 million LSLs. These estimates were revised upward to 10.2 million by USEPA, as reported in the USEPA regulatory impact analysis (RIA) for the 1991 Lead and Copper Rule (LCR) (USEPA 1991). USEPA used the same database information and findings as the AWWA effort described in Weston and EES (1990) to revise the national estimate upward, though the methodology used by USEPA is not reported (USEPA 1991). The 10.2-million estimate for the number of LSLs in the United States by USEPA in the RIA was the most-referred-to value for the number of LSLs in the United States prior to the update estimate prepared through the work conducted in this article. (either full or partial) currently present in CWSs of the United States, compared with 10.2 million estimated at the time of the original Lead and Copper Rule (LCR) (USEPA 1991); approximately 11,200 CWSs currently have LSLs compared with more than 15,000 estimated in the original LCR; 15 to 22 million people served by CWSs are estimated to have either a full or partial LSL serving their home out of a total population served by CWSs of about 293 million (7%); and approximately 30% of the CWSs surveyed (national average) reported having some LSLs in their system.

Nitrosamine data reported from the first rounds of samples collected under the second Unregulated Contaminants Monitoring Rule (UCMR2) and the Ontario Drinking Water Surveillance Program were reviewed to assess the frequency and magnitude of occurrence and the effect of disinfectant type and other treatment factors on reported nitrosamine concentrations. Initial monitoring data reveal that N‐nitrosodimethylamine (NDMA) was detected in drinking water at concentrations higher than the UCMR2 minimum reporting level (MRL) of 2 ng/L in 1 of every 10 samples. Other nitrosamines (e.g., N‐nitrosodiethylamine, N‐nitroso‐di‐n‐butylamine, N‐nitrosopyrrolidine, and N‐nitroso‐methylethylamine) were rarely detected at levels above their MRLs. NDMA was primarily detected in systems using chloramines, with more than two thirds of all chloraminated water systems detecting NDMA in at least one sample. Follow‐up survey results from 45 water systems participating in UCMR2 and 6 water systems from Ontario, Canada, generally followed expected trends based on the literature. NDMA occurrence was more frequent and concentrations were higher in water systems having long contact times with chloramines. A comparison of maximum‐residence‐time distribution system samples with entry point samples indicates that NDMA concentrations may increase in a chloraminated distribution system if precursors have not fully reacted at the entry point.

A recently developed watershed‐scale hydraulic model (De‐facto Reuse Incidence in our Nation's Consumptive Supply [DRINCS]) was applied to estimate municipal wastewater treatment plant (WWTP) contribution to downstream water treatment plant (WTP) influent flow. Using DRINCS and geocoded data for 14,651 WWTPs and 1,320 WTPs, the occurrence of treated municipal wastewater in drinking water supplies is geographically widespread, and its magnitude depends largely on the flow condition and size of the source river. Under average streamflow conditions in this study, the median contribution of wastewater flow to drinking water supplies was approximately 1% and increased to as much as 100% under low‐flow conditions (modeled by Q95). Wastewater contributions to nutrient and emerging contaminant loading were estimated and geospatially compared with the findings of the US Environmental Protection Agency's Unregulated Contaminant Monitoring Rule and Long Term 2 Enhanced Surface Water Treatment Rule. In turn, this analysis offers important insights into the treatment challenges facing treatment facilities across the United States.