Rapid Small-Scale Column Tests of Metal-based Adsorbent Media for Arsenic Removal from Groundwater Sources in California

The United States Environmental Protection Agency (EPA) lowered the maximum contaminant level (MCL) for arsenic in drinking water in 2001, effective January 2006, from 50 micrograms per liter (μg/L) to 10 μg/L resulting in increased development of arsenic removal technologies. Water systems throughout the U.S., in particular small water systems, have found it difficult to meet this MCL with the resources they have. The EPA has created a series of documents to assist these systems in choosing a cost-effective water treatment technology with recommendations for adsorption technology. When deciding on adsorption technology, there is a plethora of adsorbent media to select from, such that costs will vary drastically from one media to the other. In this work, four metal-based iron hydroxides (granular ferric hydroxide, Bayoxide E33 goethite, Metsorb G titanium dioxide, and NXT-2 lanthanum hydroxide) were compared using rapid small scale column tests (RSSCT). The RSSCTs were conducted with three groundwater sources from select communities in the Central Valley region of California to determine impacts on arsenic adsorption capacity. The breakthrough curves from the RSSCTs were used to approximate the cost of adsorption treatment with respect to replacing adsorbent media. The results of this work suggest Bayoxide E33 may be the cost effective treatment option for the small water systems that were evaluated. Interferences in effective arsenic removal include phosphorus, silica, high arsenic concentrations, low alkalinity, and high pH. The RSSCTs completed for Manteca groundwater supplies were packed with Bayoxide E33 and validated the dependence of arsenic adsorption capacity on pH, phosphorus, arsenic, and alkalinity.