The influence of the molecular weight of soil humic substances on the coagulation efficiency with aluminum sulfate was studied in this work. Four types of water were studied, with the same true color of approximately 100 HU, but prepared with different fractions of molecular weights: Water Type 1 (humic substances filtered in membrane of 0,45 µm); Water Type 2 (humic substances filtered in membrane of 0,45 µm and with molecular weight > 100 KDa); Water Type 3 (humic substances with molecular weight between 100 and 30 KDa); Water Type 4 (humic substances with molecular weight < 30 KDa). It was conclude that the higher the molecular weight of the molecules, the lower the coagulant dosages required for efficient coagulation, at the coagulation pH range 6 - 7. The types of water prepared with the fractions of humic substances containing higher concentrations of fulvic acid required higher doses of coagulant to achieve the same efficiency.
Humic substances; humic acid; fulvic acid; molecular weight; coagulation with aluminum sulfate
