Arsenic treatment considerations

The least‐cost method of removing arsenic may not be the best method all around. The best arsenic treatment technique for a given utility will depend on arsenic concentration and species in source water, other constituents in the water, existing treatment processes, treatment costs, and handling of residuals. To evaluate these issues, a national survey investigated arsenic occurrence and speciation in US drinking water sources. In general, total arsenic concentration was higher in groundwater than in surface water supplies. Particulate arsenic was more abundant than previously suspected, and more arsenate than arsenite was present. The cost of arsenic treatment increased in the following order: modified conventional treatment << activated alumina or anion exchange < reverse osmosis. Nevertheless, the most cost‐effective treatment still might not be best, because secondary treatment benefits and residuals handling should also be taken into account.