The study of coagulation process in medium turbidity removal from drinking water

Background & Aims of the Study: Colloidal impurities are one of the natural contaminants in surface water that cause turbidity and color. Turbidity in spite of create undesirable appearance, can be a haven for disinfection of microorganisms. This study aimed to evaluate the effectiveness of various coagulants in removing average turbidity of water and also their impact on the electrical conductivity and alkalinity. The study was conducted as tentative - interfere research in a laboratory scale. Experiments were carried out based on various parameters including different turbidity (50,100 and 200 NTU) and different concentrations of coagulants (5, 10, 15, 20, 25 and 30 mg/L). Supernatant of samples were taken after Jar test to measuring of turbidity, conductivity and alkalinity. The settling characteristics of the floc were record by observing as descriptive terms such as poor, fair, good and excellent. Results showed that all coagulants materials in whole used levels be able to completely remove of the initial turbidity (with the exception of Ferrous sulfate coagulant). On the other hand, with increasing concentrations of coagulants, the electrical conductivity increased and alkalinity decreased. Also, the highest and the lowest increase of electrical conductivity and TDS obtained in ferric chloride and poly aluminum chloride coagulants respectively. The result showed that poly aluminum chloride was best coagulant for turbidity removal and in spite of fine floc, sedimentation rate is good.