Investigation of Phosphorus Removal in Sewage Sludge Solid Fuel Using Citric and Formic Acid

The amount of sewage sludge continues to increase with expansion of the sewage treatment plant. However, ocean dumping of sewage sludge has been prohibited with the London Protocol for the Prevention of Marine Pollution. Therefore, it is an important issue to treatment of sewage sludge on the ground site. The hydrothermal carbonization technology is one of the attractive solutions to convert the sewage sludge into solid fuel. It can decrease sewage sludge and can produce alternative energy.

Unlike coal, the sewage sludge solid fuel contains large quantities of phosphorus. The phosphorus is commonly known as a substance that significantly impacts fouling and slagging. Fouling and slagging is a factor that lowers energy efficiency. Therefore, it is important to remove phosphorus for reducing fouling and increasing energy efficiency. In this experiment, the sewage sludge solid fuel, which was produced from Incheon city, S.Korea, was used. Citric acid and formic acid was used to dissolve phosphorus in water. Sewage sludge solid fuel mixed in citric and formic solution and stirred for 24hours. In order to investigate phosphorus removal by citric and formic acid, phosphorus-dissolved solution was analyzed by Ion Chromatography. As a result, phosphorus removal efficiency of citric acid is higher than formic acid. In order to investigate fouling property of sewage sludge solid fuel with phosphorus removed, muffle furnace experiment and agglomeration test was conducted.