Adsorptive Removal Of Arsenic And Chromium From Two California Groundwater Sources Using Rapid Small Scale Column Tests

At the federal level, the United States Environmental Protection Agency (US EPA) started enforcing a maximum contaminant level (MCL) of 10 [mu]g/L arsenic in public water systems in 2006, down from 50 [mu]g/L. As of July 1st, 2014 the state of California started enforcing a 10 [mu]g/L MCL for hexavalent chromium, formerly 50 [mu]g/L total chromium. These changes have sparked increased demand for cost effective treatment technologies for these contaminants, which has in turn driven research in the field. Iron oxide adsorbents are an established treatment method for arsenic removal, but have not been proven effective in treating chromium. Despite extensive documentation on the effectiveness of treating arsenic with iron oxide adsorbents, variations in source water qualities result in bed lifespans that must be estimated on a case-by-case basis. Scaled down adsorption tests that can be completed in 2-4 weeks, known as rapid small-scale column tests (RSSCTs), were used to conduct two studies. In one study, an established arsenic adsorbent (E-33) was subjected via RSSCT to a particular arsenic contaminated groundwater to quantify its removal capacity for that water source. In another study, a new and largely untested iron oxide adsorbent (E-33 HC) was tested in an RSSCT with chromium contaminated groundwater to measure its effectiveness for chromium removal. E-33 treated approximately 15,000 bed volumes of source water in the first study. The second study indicated that E-33 HC was not effective in removing chromium from the source water tested.