Effect of raw water quality on coagulant dosage and optimum pH

Abstract

Removal of turbidity, suspended solids (SS) and natural organic matter (NOM) using coagulation are well known because of the ability of the process in destabilizing the colloids particles and reducing the repulsion force between the particles. The objectives of the study are to explore the effect of the selected water quality parameters (i.e initial pH, initial temperature and SS) and to develop a statistical relationship between the water quality parameters and the optimum dosage and pH. The study was conducted using jar test procedures using synthetic water prepared using kaolin as the source of SS. The experiments were designed using Response Surface Method (RSM) with final turbidity as the response. RSM was found to be better approach than one-factor-at-a-time (OFAT) in determining the optimum dose and pH. Initial pH and SS was found to have significant effect to optimum dose at 90% confidence level (a = 0.1) and temperature was the only factor having significant effect on optimum pH at 80% confidence level (a = 0.2). Probably due to the complexity of the nature of the coagulation process, the relationship between the parameters and the response was only developed for optimum pH.