Adsorption isotherm studies of the simultaneous removal of turbidity and hardness by natural coagulants

Coagulation being a cost-effective method is best suited for water treatment in rural areas. Natural coagulants suited for the simultaneous removal of turbidity and hardness were investigated. In this study, the seeds of Strychnos Potatorum, the pads of Cactus Opuntia and mucilage extracted from the fruits of Coccinia Indica in synthetic turbid water were used to promote coagulation. The mechanism of turbidity removal by the use of natural coagulants was based on adsorption and charge neutralization. In addition, the adsorption mechanism of hardness removal in hard water conforms to both Langmuir and Freundlich adsorption models. Therefore, for hard water the natural coagulants tend to adsorb hardness and form a net like structure followed by turbidity removal by sweep flocculation. The potential of these natural coagulants were obtained by means of jar test study with initial turbidities of 192 NTU (High) and 28 NTU (Low). It was found that the natural coagulants can be more efficiently used for high turbid waters. Hardness removal efficiency was found to increase with the increase in coagulant dosage.