Comparison study of turbidity removal using synthetized poly-aluminum chloride-sulfate and poly-aluminum chloride in aqueous solutions

Aims: In this study, the turbidity removal efficiencies of poly-aluminum chloride (PACl) and poly-aluminum chloride-sulfate (PACS) as a coagulant in aqueous solutions were compared. Materials and Methods: PACS and PACl were prepared at experimental conditions. A conventional jar test apparatus was used for coagulation experiments. Effects of different conditions such as pH (2-12), coagulant doses of PACl (0.01-1.5 mmol/L as Al) and PACS (0.01-1.8 mmol/L as Al), settling time (0-90 min), initial turbidity (7-575 NTU) on the turbidity removal efficiency were investigated. Results: The experimental results indicated that the optimum pH during the turbidity removal was 6.5 and 9.5 for PACl and PACS, respectively. The optimum coagulant dosages of PACl and PACS were achieved 0.1 and 1.22 mmol/L as Al respectively. Under these optimal conditions, the turbidity removal efficiencies of 97.85% and 95.85% were observed for PACS and PACl, respectively. Furthermore, the effects of settling time and initial turbidity on turbidity removal efficiency were investigated. The results revealed that the turbidity removal efficiency for the PACS was slightly higher than that for PACl at the same conditions. Conclusion: PACS as a coagulant improved turbidity removal efficiency compared to PACl. PACS as a coagulant can be used for drinking water treatment. However, the dosage of PACl in comparison with PACS was lower for a similar turbidity levels. Therefore, using of PACS in comparison with PACl must be evaluated economically.