Evaluation of turbidity removal efficiency from Karun river water using polyaluminum chloride and chitosan

Abstract

This study was conducted with the aim of evaluation of turbidity removal efficiency from Karun river water using polyaluminum chloride and chitosan. Chitosan is a linear cationic polyelectrolyte with high positive electron charge (one positive charge per glucose amine unit). Chitosan is used in water purification systems as coagulant along with common coagulants (alum, chlorferric). This biopolymer is also used as a primary coagulant. Chitosan has a higher ability to coagulate colloidal particles than synthetic polyelectrolytes, most of which lack the property of biological degradation in the short term, and some of them cause carcinogenesis and genetic mutation in humans. Therefore, the use of chitosan is preferable to artificial polyelectrolytes from an environmental point of view. This research was conducted on the laboratory scale using a jar test device at the water treatment plant in Ahvaz. In this study, various parameters such as pH, polyaluminum chloride concentration and chitosan concentration were present as variables. After preparing the samples and just before starting jar tests, in the rapid mixing cycle of 200 rounds per minute, the optimal pH to remove the turbidity obtained 8. Also, the optimal dosages of polyaluminum chloride and chitosan were selected as 4 ppm and 0.04 ppm, respectively. Also the main mechanism for destabilizing clots and removing turbidity was bridging between the particles. In this condition, the removal of turbidity showed the highest efficiency. On the other hand, chitosan created clots with a higher weight and, as a result, better settling ability. Therefore, chitosan was a suitable choice to remove turbidity from water.