Investigating the feasibility of removing the rapid mixing unit in conventional surface water treatment and its effect on turbidity removal

Coagulation and flocculation processes play a major role in surface water treatment. The aim of this study was to eliminate the rapid mixing unit in the water treatment plant. This experimental study was conducted on turbid water. Turbid water was synthesized by kaolin powder. The conventional jar test method was used. The flocculation and sedimentation processes were performed on the turbid water without a rapid mixing unit for getting the new optimal condition. When the PACl coagulant was used alone and in conjunction with chitosan, the percentages of turbidity removal in low, medium and high turbidities were obtained as 86.7, 95.8, 97.8 and 86.67, 95.73, 98.26, respectively. When the rapid mixing unit was emitted, the efficiency of turbidity removal in the low turbidity was reduced from 5.26 to 21.73. But, in higher turbidity in two states (presence and absence of the rapid mixing units) it did not have a significant difference. This study showed that the removal of the rapid mix unit on the removal efficiency of turbidity in the low turbidity is effective, but does not have an effect on higher turbid water. Also, using PACl in conjunction with chitosan was effective in the removal efficiency and to reduce residual aluminum. © 2021 The Authors