Optimized Use of Ferric Chloride and Sesbania Seed Gum (SSG) as Sustainable Coagulant Aid for Turbidity Reduction in Drinking Water Treatment

Abstract

The growing global concern with environmental issues has raised the interest in the research into natural biopolymers as a coagulant aid in order to reduce the use of inorganic coagulants. This paper investigated the feasibility of sesbania seed gum (SSG) as a plant-based coagulant aid and ferric chloride as a coagulant in drinking water treatment. Acid extraction method marked the highest and most promising extraction yield at 20.8%, as compared to other extraction methods. Further, the SSG extracted carried a weak negative charge of −3.02 mV, which is classified as a near neutral coagulant aid. Hydroxyl and carboxyl functional groups, which aid in coagulation–flocculation, were found in the SSG. These physiochemical analyses results evinced good characteristics of SSG as a coagulant aid. On the other hand, response surface methodology (RSM) with three-factor Box–Behnken design (BBD) was employed to evaluate and optimize the reaction condition of the coagulation–flocculation process in drinking water treatment. A quadratic polynomial model was fitted to the data with a high value of R2 (0.9901). Model validation experiments revealed the good correspondence between actual and predicted values. In drinking water treatment, a promising 98.3% turbidity reduction was achieved with 10.2 mg/L of FeCl3 and 4.52 mg/L of SSG. Therefore, SSG exhibited potential as a coagulant aid in drinking water treatment.