Abstract:
The objective of this study was subjected to some parameters affected arsenic removing in form of arsenite and arsenate by coagulation process. The studied parameters were pH, type and guantity of coagulants, forms of arsenic as well as efficiency of chlorine. The selected pH was limited at 6.5 to 8.5. The range of 20 to 40 mg/l. was applied to all three coagulants, alum, ferric chloride and ferric sulphate. The study was carried out by means of laboratory jar-test then followed by spectrophotometric method for analysis of arsenic by silver diethyldithiocarbamate measured at 535 nm. It was found that ferric sulphate was the mast effective coagulant to remove arsenite in synthetic water at pH 6.5-8.0. And in natural water ferric sulphate could reduce arsenic to less than 0.058 mg/l. Alum could remove arsenate in synthetic water samples where as ferric chloride had a better efficiency of removing arsenite than arsenate but the residual was still higher than the Who guide-line value (0.05 mg/l) The efficiency of arsenic removal by alum and ferric chloride at pH6.5-8.5 had no significant difference (=0.05). However, oxidation with chlorine followed by coagulation process yielded remarkable results for arsenic removal with statistical significance at α =0.05.