Using Bentonite Clay as Coagulant Aid for Removing Low to Medium Turbidity Levels

Alum is a widely used coagulant around the world, but its use of it is associated with some problems, as it increases the aluminum residuals, which have been linked to Alzheimer s disease. Coagulant aids may help with reducing the needed dose of alum. In this paper, many sets of experiments were done to determine the effect of using bentonite clay as a coagulation aid. The experiments were performed under different conditions and on different seasonal circumstances, where many alum and bentonite clay doses were used at low to medium initial turbidity levels. It was found that the addition of a small dose of bentonite clay; 5 mg/L improves the coagulation efficiency between 5 to 7.5 % for the Alum dose 10 mg/L and between 10.6 to 14% for the alum dose 15 mg/L . The coagulation process was also studied by changing both the temperature and the pH value; the best performance of bentonite was when pH is 5 and 6, and when the temperature changed between 10 to 25, the improvement of the removal percentage was about 30 % for the low turbidity and about 9% for the high ones. Finally, the effect of changing the settling time and the mixing speed were also studied. In this regard, it was observed that the best settling time was 90min and the best stirring speed was 200 rpm.