AWWA ACE63228

This slide presentation outlines a study on arsenic removal using a process of Oxidation-Coagulation-Recirculation- Filtration that includes: oxidation of arsenic with liquid sodium hypochlorite or solid calcium hypochlorite tablets; coagulation of arsenic with iron coagulant selected 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 of silica and iron contaminates; and, a plant trial in southwest Arizona of high pH water and silica and sulfate contaminates. A summary of results verified by the ETV study include: all operations performed by NSF; all samples analyzed by NSF laboratory; filtrate water averaged 3 ppb; system found easy to operate and required little maintenance; estimated time to check system is minimal; and, PLC set up so main parameters can be monitored without a site visit. A summary of results for the Arizona study include: system monitoring equipment works well; unit design is conservative and can handle increases in flow; for a 30 day trial effluent arsenic averaged 2.6 ug/l; and, process was able to remove arsenic to below 8 ug/l with an iron dose of .48 ppm. Includes tables, figures.