Effect of Oxidation Coefficient on Products of Sewage Sludge Treatment in Supercritical Water

Supercritical water treatment is a promising technology for sewage sludge disposal. The influences of oxidation coefficient (OC) as well as temperature on products of sewage sludge treatment in supercritical water were studied systematically. The results show that CO₂ yield obviously increased with raising OC or temperature. Oxidant helped to convert N-containing compounds into N₂. A small amount of oxidant increased H₂ yield but excess oxidant decreased it. OC had significant effect on the COD (chemical oxygen demand) and NH₃-N (ammonia nitrogen) concentration of liquid products. Most of organic compounds disappeared at OC=1.0 as temperature changed from 450 to 500, and diethyl phthalate was main stubborn substance in the liquid phase. The contents of some elements (such as Si, Al and Ca) in solid residue was almost double compared with those in dry basis SS.