Application of the Coagulation Process Focusing on Humic Substances

The water source for Ogasawara village in Tokyo Prefecture has high concentrations of organic matter, color, and high trihalomethane formation potential. Therefore, the fungal breakdown of plants has produced leaf mold, which in turn has caused surface runoff to contain various humicsubstances. At the Ogiura water purification plant, a flocculant is added by a high injection ratio of 200-400 mg/L for removal of humicsubstances. This research focuses on humic substances in raw water in order to develop a means of separating humic acid with pH adjustment. The result shows that humic acid of raw water for water supply and purification treatment could be reduced and that the amount of chemical used for coagulation treatment could furthermore be reduced by optimal pH and PAC injection ratio under laboratory conditions. The results should serve as useful information for improving the purification treatment in areas that use raw water containing high levels of humic substances for their water supplies.