Optimization of Coagulation to Remove Turbidity from Surface Water Using Novel Nature-Based Plant Coagulant and Response Surface Methodology

Abstract

Plant-based natural coagulants are considered potential alternatives to chemical coagulants. These are eco-friendly, non-toxic, and produce less sludge compared to chemical coagulants. This study aims to evaluate the coagulation potential of a novel plant-based coagulant Sorghum for canal water treatment. In addition, a coagulant aid, i.e., Aloe Vera, was also tested to examine any further increase in turbidity removal through a jar test apparatus. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were used to characterize the coagulants. The experiment was designed using response surface methodology (RSM). When used alone, Sorghum resulted in a maximum turbidity removal of 87.73% at pH 2 and a dose of 40 mg/L, while the combination of Sorghum and Aloe Vera resulted in a turbidity removal of 84.2% at pH 2.7, and the doses of Sorghum and Aloe Vera were 17.1 mg/L and 0.9% (v/v), respectively. Thus, the Sorghum dose was significantly reduced when Aloe Vera was used in combination. At a pH of 7, Sorghum achieved 54% turbidity removal at a dose of 55.7 mg/L. Analyses of variance revealed that pH plays a more vital role in the removal of turbidity than the coagulant dose. FTIR and SEM analyses revealed that adsorption is the dominant coagulation mechanism for plant-based coagulants. The Sorghum powder exhibited carboxylic, amine, and carbonyl groups that functioned as active adsorption sites for suspended solids. In a similar vein, the coagulant aid Aloe Vera gel facilitated the adsorption process by fostering intermolecular hydrogen bonding between suspended particles and amine groups present within the gel.