Mechanism of turbidity and hardness removal in hard water sources by using Moringa oleifera

Abstract

The objective of this study was to describe the mechanism of simultaneous removal of hardness and background turbidity in hard water for drinking water purpose by using Moringa oleifera (MO) that extracted with 1.0 M sodium chloride solution (MO-NaCl). Raw water containing high concentration of hardness from Timah Tasoh Dam (Perlis, Malaysia) and synthetic water (turbid, hard, turbid and hard) were used in this study. The optimum turbidity removal efficiency of Timah Tasoh raw water, synthetic turbid water and synthetic turbid and hard water were approximately 80% which were attained at MO dosage of 15, 30 and 10 mg L-1, respectively. However, this optimum MO dosage was not applicable for hardness removal. The mechanism for turbidity removal by MO-NaCl was supposed to be adsorption and charge neutralization, with the adsorption isotherm following the Freundlich adsorption model. In addition, the mechanism for hardness removal in hard water seems to be adsorption that conforms to both Freundlich and Langmuir adsorption models. Therefore, for hard water such as Timah Tasoh raw water and synthetic turbid and hard water, the MO-NaCl tends to adsorb hardness to form a netlike structure followed by turbidity removal through sweep coagulation mechanism. Hence, hardness and turbidity can be removed simultaneously by using MO-NaCl.