Full metadata
Title
Occurrence and treatment of hexavalent chromium and arsenic in Arizona municipal and industrial waters
Description
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.
Date Created
2014
Contributors
- Bowen, Alexandra (Author)
- Paul, Westerhoff K. (Thesis advisor)
- Hristovski, Kiril (Committee member)
- Halden, Rolf (Committee member)
- Arizona State University (Publisher)
Topical Subject
- Environmental engineering
- Chemistry
- Arsenic
- Drinking water
- Hexavalent Chromium
- industrial water
- Ion Exchange
- water treatment
- Groundwater--Purification--Chromium removal--Arizona.
- Groundwater
- Groundwater--Purification--Arsenic removal--Arizona.
- Groundwater
- Water--Purification--Ion exchange process--Arizona.
- Water
Resource Type
Extent
xi, 94 p. : ill. (some col.)
Language
eng
Copyright Statement
In Copyright
Primary Member of
Peer-reviewed
No
Open Access
No
Handle
https://hdl.handle.net/2286/R.I.25147
Statement of Responsibility
by Alexandra Bowen
Description Source
Viewed on July 2, 2014
Level of coding
full
Note
Vita
thesis
Partial requirement for: M.S., Arizona State University, 2014
bibliography
Includes bibliographical references (p. 88-90)
Field of study: Civil and environmental engineering
System Created
- 2014-06-09 02:19:21
System Modified
- 2021-08-30 01:33:55
- 3 years 2 months ago
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