A study on improvement of dewater ability of sewage sludge using coal ash through cst

Sewage sludge in South Korea was generated 9,810.5 tons/day and Sludge treatment costs account for 25~50% of total wastewater treatment costs, so sludge dewatering and reduction are needed. About 20.4% of the generated sewage sludge is recycled as fuel, but it takes a lot of energy and cost to dewater and dry sewage sludge with high moisture content. Therefore, this study investigated whether coal ash, which is easy to dewater, can be used as an agent to improve the dewaterability of sewage sludge which is difficult to dewater due to high cake specific resistance through CST (Capillary Suction Time).CST was measured by adding 1, 3, 5, 7 and 10% of coal ash incinerated for more than 12 hours at 700℃ to the excess sludge generated from S sewage treatment plant. Andthe pH of each mixed sample was measured to determine the effect of coal ash on the pH of sewage sludge. As a result, it is expected that the use of coal ash as an agent to improve will not affect the pH of sewage sludge and it will not be a problem when used with other flocculants. Also, when 1% of coal ash was added to the sewage sludge, the CST was decreased by about 16% or more. This suggests that coal ash can be used as an agent to improve sludge dewaterability.