Application of response surface methodology to optimize removal efficiency of water turbidity by low-cost natural coagulant (Odaracha soil) from Saketa District, Ethiopia

Abstract

Turbidity removal is a meaningful activity in the water treatment system, and it is an indicator of water quality. With this, natural coagulants are desirable and economical ways of removing water turbidity. The purpose of this study was to investigate the turbidity removal efficiency of Odaracha soil from river water. A coagulation experiment was carried out using a standard procedure for a jar test. 300 mL of water sample was added into a beaker by adjusting the water pH to the desired value. Different coagulant doses are added and mixed for 2 min by 250 rpm, then agitated for 10 min by 45 rpm. Finally, the sample was unflustered for different settling times. Response surface methodology (RSM) was also applied to optimize the process and estimate the interaction influence of the operating variables. According to the experimental result of this study, at the optimum condition (pH 7, 0.5 hrs settling time, and 3 g/L of coagulant dose), the turbidity removal efficiency of Odaracha was 88.13%. In contrast, the predicted turbidity removal efficiency was 90.54%, which indicates the consistency between the actual and the anticipated results. Correspondingly the R2 value (0.9922) confirmed a high correlation between the real and predicted values. Generally, the quadratic model's actual and predicted results confirmed the turbidity removal capability of Odaracha and the significant effects of all the individual parameters and their interaction effects (except the interaction between the dose and settling time).