Arsenate removal from drinking water by coagulation and flocculation

Arsenic is a natural element that can found into water sources and cause serious health problems due to its harmful effects. High levels of arsenic in drinking water directly affect people's life quality and health. In this thesis, the coagulation and flocculation method was evaluated for the removal of arsenate from drinking water, using iron (III) chloride and iron (III) sulfate as coagulants. The study investigated the effects of pH value, type and amount of coagulant, and initial arsenate concentration on the efficiency of arsenate removal. Additionally, the effect of using three different types of polyelectrolytes— anionic, cationic, and nonionic—on the efficiency of arsenate removal in terms of both quantity and type was examined. According to the results of the study, the optimum pH value for iron (III) chloride was determined as 7, and for iron (III) sulfate, it was 8. For the amount of coagulant, 50 mg/L for iron (III) chloride and 40 mg/L for iron (III) sulfate were shown to provide the most effective removal rates. Increases beyond these amounts did not significantly improve removal efficiency. In experiments conducted to determine the effect of initial arsenate concentration on removal, both coagulants achieved higher efficiencies with higher initial arsenate concentrations, yet all tested initial arsenate concentration values resulted in residual arsenic levels in the water below the permissible maximum contaminant level of 10 ppb. The use of polyelectrolytes, particularly the addition of cationic polyelectrolytes, significantly increased the removal efficiency in the experiments with both coagulants. The research was proven that the coagulation and flocculation method, using iron-based coagulants and polyelectrolytes, is a suitable method for arsenic removal from drinking water. The selection of optimal pH levels, coagulant type and amount, along with appropriate polyelectrolytes, was achieved significant efficiency in removing arsenate from drinking water.