new Arsenic standard Spurs Search for Cost‐Effective Removal Techniques

The new maximum contaminant level for arsenic in drinking water will require many water authorities to add unit operations for arsenic removal. A recent study conducted on groundwater from a small rural city in Colorado investigated removing arsenic by modified coagulation/filtration. On the basis of the results of the study, modified coagulation/filtration was proven to be a practical process for removing arsenic from groundwater. Coagulation by ferric chloride and ferric sulfate produced similar residual arsenic concentrations, although ferric sulfate gave a lower residual turbidity. Adjustment of the pH of the groundwater is likely to be necessary. A ferric ion dose of 6 mg/L and an initial pH of 6.8 gave a residual arsenic concentration of 2 μg/L or less, depending on the pore size of the membrane filter disks. These results are in agreement with previous studies conducted using carefully prepared arsenic solutions. However, the level of arsenic removal from groundwater is highly dependent on the water quality.