Removal of arsenic from contaminated water by coagulation followed by polyelectrolyte enhanced ultrafiltration

In this work, removal of arsenic from contaminated water was carried out using coagulation followed by polyelectrolyte enhanced ultrafiltration (PEUF). Ferric chloride and polydiallyldimethylammonium chloride (polyDADMAC) were used as coagulant and cationic polyelectrolyte, respectively. In the first step, effect of coagulant concentration on removal of arsenic was studied and coagulant dosage was optimized. In the second set of study, a combination of low dose of coagulant and polyelectrolyte solution was used for treatment of arsenic contaminated water. The supernatant collected following coagulation was subjected to PEUF so as to remove the residual arsenate ions. Ultrafiltration (UF) was carried out in a tangential flow module fitted with 5 kD polyethersulfone (PES) membrane. During UF, influence of polyelectrolyte dosage and transmembrane pressure (TMP) on permeate flux and arsenic rejection were investigated and optimum values were reported. It was observed that small dose [1mL PE (polyelectrolyte)/50mL of sample] could effectively reduce the residual arsenic concentration below permissible maximum contaminant level of 10ppb. A 99.2% rejection of arsenic was recorded during ultrafiltration at a TMP of 2.5bar following treatment with 0.234mM polyelectrolyte solution.