Coagulation and Flocculation are essential processes for turbidity removal from natural waters. Many studies have been conducted on different coagulants.
The aim of this study was to inestigate the removal efficiency of turbidity, Coliform bacteria and heterotrophic bacteria from natural water by Poly Aluminum Chloride (PAC). The study was conducted in the lab scale in Ahwaz No.2 water treatment plant. To determine the optimum conditions of PAC in the removal of turbidity, Coliform bacteria and heterotrophic bacteria, the experimental set up in coagulant variable doses (3, 5,8,10,15,20,30,40,50 mg/lit), pH variable (5.5, 6, 6.5, 7, 7.5, 8) and turbidity in the range of 33-100 NTU were performed. At the end of any run, residual turbidity and microbial parameters were measured in the treated water. The performance of coagulant for removing of turbidity and microbial population was determined by analysis of Covariance and Duncan.
The results showed that the most optimal conditions of PAC for removal of turbidity and microbial parameters was performed in pH = 8, flash mixing =120 rpm and optimal concentrations of 10 and 30 ppm of PAC.
Removal efficiency of turbidity, total Coliform, fecal Coliform and heterotrophic bacteria in optimum condition of PAC for Concentrotion of 10 ppm was 96.59%, 90%, 82.75% and 84.17%, respectively, while removal efficiency of turbidity, total Coliform, fecal coliform and heterotrophic bacteria in optimum Condition of PAC in the Concentrotion of 30 ppm was 99%, 94.65% , 88.94% and 90.47% respectively.