This report presents the results of a laboratory study to evaluate several potential treatment options to treat residuals produced by five drinking water treatment processes; ion exchange (IE), reverse osmosis (RO), nanofiltration (NF), activated alumina (AA) and iron removal methods. The treatment processes evaluated were precipitation and adsorption. Residuals used in the studies were collected from arsenic removal facilities or from non-arsenic removal facilities whose residuals were spiked with arsenic. The precipitation test results showed that ferric chloride out performed alum generally resulting in arsenic removals of 88 to 99 percent except for the high alkalinity ion exchange residuals whose removal were lower. Best removals occurred at pH 5.0-6.2 and polymer addition typically did not improve removal with either coagulant. Adsorption tests for the removal of arsenic from liquid wastes showed an iron based medial to out perform aluminum based media and ion exchanges resins. Activated alumina and the iron based media provided comparable removals of close to 100 percent with an empty bed contact times of 3-min. Arsenic breakthrough occurred very rapidly for the ion exchange residuals and one RO concentrate both of which had high alkalinity. Of all of the residuals streams tested, the IE regenerants were the most difficult to treat. Toxicity charactistic leaching procedure (TCLP) tests on all final residuals produced including solid media samples by the arsenic removal processes had arsenic results far below the current regulatory limit of mg/L and were generally below 0.5 mg/L.

"June 2001." Includes bibliographical references (p. 59-60). "EPA/600/R-01/033." "Contract no. 8C-R613-NTSA."