Arsenate removal by coagulation using iron salts and organic polymers

Abstract

Arsenic occurs naturally in the water in many parts of the world. The coagulation and flocculation method is used for arsenate removal from drinking water using ferric chloride, ferric sulfate, and ferrous sulfate. The effects of coagulant type and dosage on removal efficiency of arsenate are determined by considering the residual iron after sedimentation and filtration in the effluent. At the same time the impact of the type (cationic, anionic, and nonionic) and dosage of organic polymers on the removal efficiency of arsenate was investigated. Residual arsenate concentrations were decreased below 10 mg L-1 for ferric chloride and ferrous sulfate concentration of 30 and 80 mg L-1, respectively. Ferric chloride provided minimum and acceptable residual iron concentration (175 mg L-1) after sedimentation and filtration and it was determined as the most effective and economic coagulant type because it requires lower amounts than the others and produces minimum residual iron. The addition of cationic polyelectrolyte aided maximum arsenate removal efficiency although all types of polymers increased the efficiency of the treatment method. The percentage of removal reached a maximum level at the cationic polyelectrolyte concentration of 2.5, 2, and 3 mg L-1 for ferric chloride, ferric sulfate, and ferrous sulfate, respectively.