The current EPA regulation for total chromium in drinking water is the MCL standard of 0.1 milligrams per liter or 100 parts per billion (ppb) to avoid dermatological effects. With a toxicology study released in 2008 by the Department of Health and Human Services noting that hexavalent chromium is carcinogenic, the EPA is currently reviewing this MCL standard. During this review, the EPA provides monitoring guidance that requires quarterly sampling of surface water for hexavalent chromium. However, these samples monitor the instant in time that they were taken, and do not account for varying concentrations that are time-dependent. This research seeks to develop a method for monitoring hexavalent chromium in water. Using ion exchange technology, passive samplers were developed and installed at the Chandler Water Treatment Plant for a week-long monitoring event. Results show that passive samplers using ion exchange technology provide an accurate assessment of the average concentration of total chromium within the water treatment plant's effluent with 90.3% recovery of Cr(VI) in SIR-100 resin and 62.6% recovery in SIR-700.

Arsenic (As) and chromium (Cr) occur naturally in AZ surface and groundwaters, pose different health impacts, and exhibit different treatment efficacies. Hexavalent chromium (Cr(VI)) has newly recognized human health concerns, and State and Federal agencies are evaluating a low Cr(VI)-specific maximum contaminant level (MCL) for drinking water. Occurrence of Cr and As in municipal drinking waters and industrial cooling tower waters was quantified by grab samples and compared with sampling results obtained from a new passive sampler developed specifically for Cr(VI). Cr(VI) and As concentrations in groundwater used for cooling tower make-up water concentrations were ~3 ppb and ~4 ppb, respectively, and were concentrated significantly in blowdown water (~20 ppb and ~40 ppb). Based upon pending Cr(VI), As, and other metal regulations, these blowdown waters will need routine monitoring and treatment. Cr(VI) concentrations in a water treatment plant (WTP) raw and finished water samples varied from 0.5 and 2 ppb for grab samples collected every 4 hours for 7 consecutive days using an ISCO sampler. The development of an ion exchange (IX) based passive sampler was validated in the field at the WTP and yielded an average exposure within 1 standard deviation of ISCO sampler grab data. Sampling at both the WTP and cooling towers suggested sources of Cr(III) from treatment chemicals or wood preservatives may exist. Since both facilities use chlorine oxidants, I quantified the apparent (pH=5) second-order rate constant for aqueous chlorine (HOCl/OCl-) with Cr(III) to form Cr(VI) as 0.7 M-1s-1. Under typical conditions (2 ppb Cr(III) ; 2 mg/L Cl2) the half-life for the conversion of Cr(III) to the more toxic form Cr(VI) is 4.7 hours. The occurrence studies in AZ and CA show the Cr(VI) and As treatment of groundwaters will be required to meet stringent Cr(VI) regulations. IX technologies, both strong base anion (SBA) and weak base anion (WBA) resin types were screened (and compared) for Cr removal. The SBA IX process for As removal was optimized by utilizing a reactive iron coagulation and filtration (RCF) process to treat spent IX brine, which was then reused to for SBA resin regeneration.