Partial Replacement of Alum Coagulant by Green Coagulant: A Novel Approach for Removing Turbidity from Kaolin Synthetic Water

Turbidity is of great concern in drinking water treatment. Coagulation-flocculation (CF) process is widely applied for removing turbidity, which depends on coagulant type. Alum-chemical coagulant is commonly used due to its superiority in removing it. However, alum has been associated with several adverse impacts on human health and the environment. Natural coagulants (eco-friendly materials) cannot be a feasible alternative to alum due to their limited coagulating performance in turbidity removal. In our previous research, novel approach to reduce alum impact by partially replacing it with natural coagulant was developed based on two consecutive treatments of CF process. Its concept was that a natural coagulant was used in primary treatment to significantly reduce turbidity and alum was used in secondary treatment at a minimum dose. This approach was successfully applied for treating bentonite turbid water. To verify if its concept is feasible for treating kaolin turbid water, this research was carried out.Experimental results showed that the novel approach achieved superior performance in reducing turbidity of treated water from 950 NTU to less than 5 NTU (i.e., satisfying the WHO drinking water standards) and decreasing alum dose required by 33 and 50% using palm bark and watermelon coagulants, respectively when compared with alum control treatment (i.e., replacing partially alum). The novel approach findings in current research are consistent with our previous research. Concluding its concept is validated with two types of bentonite and kaolin turbid waters. Further work needs to verify if its concept is feasible for treating river surface water.