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 flow-through pilot-scale system was tested for removal of Cr(VI) from contaminated groundwater in Glendale, California. The process consisted of the reduction of Cr(VI) to Cr(lll) using ferrous sulfate followed by coagulation and filtration. Results indicated that the technology could reduce influent Cr(VI) concentrations of 100 microg L(-1) to below detectable levels and also remove total Cr (Cr(VI) plus Cr(lll)) to very low concentrations (< 5 microg L(-1)) under optimized conditions. Complete reduction of Cr(VI) to Cr(lll) was accomplished with Fe(ll) doses of 10-50 times the Cr(Vl) concentration even in the presence of significant dissolved oxygen levels. The overall Cr removal efficiency was largely determined by the filterability of Cr(lll) and Fe(lll) precipitates, of which a relatively high filtration pH (7.5-7.6) and high filter loading rate (6 gpm ft(-2)) had negative impacts. The pilot system was able to operate for an extended time period (23-46 h depending on the Fe:Cr mass ratio) before turbidity breakthrough or high head loss. Backwash water was effectively settled with low doses (0.2-1.0 mg L(-1)) of high molecular weight polymer. Backwash solids were found to be nonhazardous bythe toxicity characteristic leaching procedure but hazardous by the California waste extraction test.

The goal of this research was the initial evaluation of several pilot‐scale treatment technologies for hexavalent chromium removal to <5 μg/L (i.e., 95% removal). A major focus was to assess manufacturer‐provided pilot systems with media that were effective in bench‐scale studies as well as technologies that were promising but could not be appropriately tested at bench scale. The technologies tested included ion exchange systems (i.e., column strong‐base and weak‐base anion exchange and reactor‐based strong‐base anion exchange), a reduction/filtration unit using sodium sulfite, and proprietary adsorptive media systems (zeolite and granular activated carbon). In vendor‐independent tests, reduction with ferrous sulfate, coagulation, and filtration was also evaluated. Regeneration efficiency was determined for the best‐performing strong‐base anion exchange resin, including the effect of recycling brine to minimize residuals. Technologies able to consistently treat to concentrations <5 μg/L included column strong‐base anion exchange, weak‐base anion exchange, and reduction–coagulation–filtration using ferrous sulfate.

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