Arsenic adsorptive media technology selection strategies

More stringent arsenic regulations are requiring water utilities of all sizes to install treatment systems on wells which historically only had chlorination. A case study is presented for evaluating arsenic adsorption media at a well site in Mesa, Arizona, but the approach and methodological conclusions are transferable to any arsenic treatment system. The goal of this project is to develop a comprehensive, cost-effective and rapid approach for selecting arsenic adsorptive media. Batch laboratory tests, labscale continuous flow column tests and pilot-scale tests were conducted to evaluate removal efficiency, robustness, operational benefits and cost effectiveness of eight different commercially available adsorbents. Batch tests conducted at multiple pH levels provided limited benefit when compared against continuous flow rapid small-scale column tests (RSSCTs) to evaluate arsenic removal capability by different media. Breakthrough curves of arsenic, vanadium, silica and other trace metals corresponded well between lab-scale RSSCT and field-based pilot scale, suggesting that RSSCTs offer a timesaving approach for adsorptive media selection. Leaching tests on spent media verified that media could be safely disposed and high-resolution microscopic analysis indicated that calcium and silica accumulate on media surfaces and affect the longevity of arsenic removal systems.

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