Removal of turbidity, colour and organic matter from surface water by coagulation with polyaluminium chlorides and with activated carbon as coagulant aid

The aim of the research work was to evaluate the capability of pre-hydrolysed aluminium salts to reduce turbidity, colour and organic matter from surface water. The coagulants used in the study were Al-2(SO4)(3) and hydrolysed polyaluminium chlorides: PAX18, PAX-XL3, PAX-XL10, PAX-XL 19F, PAX-XL1905, PAX-XL61 and PAX-XL69. Using pre-hydrolysed saltspolyaluminium chloridesmade it possible to obtain better effects of surface water treatment compared with the results accomplished with non-hydrolysed aluminium salt (aluminium sulphate). At a dose of 3mg AlL-1 the best effects of turbidity, colour and organic matter removal were obtained using PAX-XL1905, which is polyaluminium chloride of high alkalinity. Under these conditions, 89% reduction in turbidity and 50% in colour was achieved. Moreover, the total organic carbon (TOC) value decreased by 26%. When pH was decreased from 8.2 to 6.2 the effectiveness of TOC removal increased (upto 37%). The addition of powdered activated carbon to water during coagulation did not significantly affect the effectiveness of organic compounds removal.