Enhanced aluminum coagulation processes with respect to efficient removal of Natural Organic Matter (NOM) has gained a lot of focus in many countries over the last years. Effective removal of NOM from low-turbidity waters can be achieved by aluminum coagulation. Coagulation and flocculation experiments were conducted using small-scale jar testing for treatment of two types of raw water rich in NOM and low in turbidity. Particular attention was paid to coagulation and flocculation. This paper presents guidelines and an explanation of how pH should be controlled to maximize NOM removal while at the same time making full use of pH-influencing chemicals. For low-turbidity waters, the lime that is used can provide essential floc nucleating sites. Adjusting the pH downwards to between 4.5 and 5.5 prior to coagulant addition allows the formation of NOM-aluminum complexes that link to each other, thereby forming large insoluble bridged complexes, that also act as nuclei for macro-floc development. |
