AWWA JAW56685

Effective Jan. 23, 2006, the maximum contaminant level (MCL) for arsenic (As) will be reduced from 50 to 10 ug/L, and removing As to meet the new MCL is anticipated to cost US utilities $0.2-0.7 billion per year. These compliance costs will be greatly reduced if innovative As-removal technologies are proven and implemented. Using a jar-test protocol, this study evaluated the performance of conventional coagulation/sedimentation, microsand-ballasted coagulation, coagulation-assisted microfiltration, and microsand-ballasted coagulation/microfiltration to compare the relative effectiveness of innovative coagulation- based treatment processes on As removal. The various technologies were evaluated in waters that simulated a variety of common surface water and groundwater conditions. Microsand-ballasted coagulation provided promising As removal in bench-scale tests of simulated waters; however, no synergistic benefits were observed when it was used as a pretreatment to microfiltration. Polymer was critically important to the performance of the microsand-ballasted coagulation process. Although coagulation/microfiltration typically provided the best As removal at a given iron dose, microsand-ballasted coagulation processes are likely to be a promising alternative method of As treatment if their lower projected capital and operating costs are proven valid. Utilities screening for least-cost As-removal techniques to meet the new As MCL may find this protocol useful in evaluating potential treatment technologies. Includes 10 references, tables, figures.