Evaluation of pH Adjustment Chemical for Arsenic-Fluoride Removal Using Activated Alumina

Arsenic and fluoride are co-existing contaminants commonly found in groundwater used for drinking water supply and often exceeding drinking water maximum contaminant levels of 10 µg/L and 4 mg/L, respectively. Adsorption and coagulation followed by filtration are technologies used for treatment. The USA-EPA has identified alumina adsorption as the best available technology. While arsenic removal with activated alumina was not pH-dependent in this study, fluoride removal was pH dependent, with an optimal range between 5.0 - 6.0. A bench study was conducted comparing sulfuric acid, hydrochloric acid, and carbon dioxide as alternatives for pH adjustment. While arsenic and fluoride removal were independent of chemicals used for pH adjustment, the costs of pH adjustment with carbon dioxide and sulfuric acid were similar for the site considered, indicating that carbon dioxide can be a safer and better alternative for pH adjustment if a carbon dioxide generating facility is closer to treatment site.