This slide presentation outlines a study on arsenic removal using a process ofOxidation-Coagulation-Recirculation-Filtration that includes:oxidation of arsenic with liquid sodiumhypochlorite or solid calcium hypochloritetablets;coagulation of arsenic with iron coagulantselected for raw water characteristics;recirculation of 10-30% of flow; and,filtration, using a standard mix of sand, gravel,and garnet in a media filter. Two case studies verifying the process are outlined and include:ETV Study in Chelsea, Michigan ofsilica and iron contaminates; and, aplant trial in southwest Arizona ofhigh pH water andsilica and sulfate contaminates. A summary of results verified by the ETVstudy include:all operations performed by NSF;all samples analyzed by NSF laboratory;filtrate water averaged 3 ppb;system found easy to operate andrequired little maintenance;estimated time to check system is minimal; and,PLC set up so main parameters can bemonitored without a site visit. A summary of results for the Arizona study include:system monitoring equipment works well;unit design is conservative and can handleincreases in flow;for a 30 day trial effluent arsenic averaged2.6 ug/l; and,process was able to remove arsenic tobelow 8 ug/l with an iron dose of .48 ppm. Includes tables, figures.
Keywords: Arsenic; Filtration; Iron; Arizona; Coagulation; Silica; Equipment
