Comparative Evaluation of Glycine max L. and Alum for Turbid Water Treatment

摘要

Disadvantages associated with chemical coagulants and goal of sustainable development have shifted the focus to natural plant-based coagulants. Raw and defatted soybean (Glycine max L.) seed powder, as innovative and eco-friendly coagulant, was appraised in detail for turbid water treatment and compared with alum in this study. Design of experiments was conducted by employing response surface method which lacks in past studies pertaining to plant-based coagulants. Experiments were conducted with lab prepared turbid water with initial turbidity of 200 NTU and wide range of pH (2-10) and dose (20-100 mg/L). Results revealed that raw and defatted soybean gave residual turbidities of 4 and 3 NTU at optimum conditions which were comparable to alum. Analysis of variance (ANOVA) identified that pH was more significant parameter as compared with dose for soybean and alum, while interaction of pH and dose was most significant in case of defatted soybean. Characterization of the coagulants and flocs, by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM), revealed that postulated mechanism of coagulation for plant-based coagulants is adsorption and charge neutralization. Cost of treating 1000 m(3) of water by raw and defatted soybean is lower (US$12 and US$3.9 respectively) compared with alum (US$31.2).