Efficiency of the chitosan as natural coagulant with PAC in removing turbidity from Municipal water treatment plant (case study: Ahvaz water treatment plant)

Karun River is the largest and most watery river in Iran. This river is the longest river which located just inside Iran and Ahvaz Metropolis drinking water supplied from Karun River as well . Karun River as the main source of water treatment plants in Ahvaz, like most surface waters affected by various contaminants which caused changes in water quality of the river .Chitosan is a biodegradable cationic polymer derived from the deacetylation of chitin. This study aims to investigate the effects of chitosan as a coagulant aid for the improvement of a polyaluminum chloride coagulant in removing the turbidity from drinking water. This study was conducted in the laboratory using a jar test in the water treatment plant of Ahvaz, Iran. Experiments were conducted based on various variables such as concentration of coagulant, pH, and different concentrations of chitosan as a coagulant aid. After preparation in a jar test, samples were mixed fast at 120 rpm for 1 min and slowly at 30 rpm for 15 min and remained under stable conditions for 30 min to allow for settlement. The optimal pH for the removal of the turbidity was pH 8. The optimal dosage of polyaluminum chloride combined with chitosan was 5 and 0.02 mg/L, respectively. Under optimal conditions, the use of chitosan could reduce the concentration of polyaluminum chloride by approximately 50%. The investigation showed that the optimal concentration of PAC for turbidity removal was 10 mg/L. When the PAC concentration was adjusted to 10mg/L, adding 0.02mg/L of chitosan to the process, maximum turbidity removal was achieved at 99.16%. In addition, particles formed in flocculation by chitosan were coarser and settled faster. Results indicated good performance of chitosan as a coagulant aid for the removal of the turbidity from drinking water.

Keywords:

karun river , Coagulation , Turbidity , Chitosan , Polyaluminum chloride , Water treatment plant