Investigation of Submerged Membrane Reactor in Removal of Water Turbidity Using Poly-Aluminum Chloride Coagulant with Coagulation Aids of Polyelectrolyte and Lime

In recent years, the development of submerged membrane systems has led to the significant development of ultrafiltration/water purification markets. The study aimed to investigate the efficiency of Poly-Aluminum Chloride coagulant in removing turbidity using a submerged membrane reactor for simultaneous coagulation and flocculation of filtration and determine the optimal values of its performance parameters. In this study, the Poly-Aluminum Chloride coagulant along with lime and polyelectrolyte for water coagulation and flocculation was firstly evaluated by the Jar test in different turbidities. Also, pH (5-10), Poly-Aluminum Chloride (1-50 mg/L), and coagulant aids of lime (0.5-15 mg/L) and polyelectrolyte (0.1 to 2 mg/L) were examined. Then, a pilot-scale submerged membrane reactor was designed for coagulation, flocculation, and membrane filtration processes. Pilot experiments were used as closed systems, and then different parameters of flux, aluminum concentration in the treated water, and membrane fouling were investigated. Jar test results showed that Poly-Aluminum Chloride had a great performance in removing turbidity. In addition, the use of lime and polyelectrolyte coagulant aids improved the turbidity removal process by 3%. Furthermore, pH=8 was selected as the optimal range, and the best flux performance was obtained at turbidity less than 100NTU in a submerged membrane pilot. The flux reduction in eight hours of operation time was only 5% while this increased to 50% in turbidity above 200NTU. The turbidity removal percentages were reported to be constant and higher than 99.5%. The removal rate of total aluminum by the membrane process has been over 99%, and the type of membrane fouling is surface sediment and is reversible. Results indicated that the submerged membrane reactor along with coagulation and flocculation could be applied as an efficient method in water treatment with different turbidity.