Abstract: The improvement of sludge dewater ability is essential to the volume reduction of waste activated sludge (WAS). The wet air oxidation process is used for WAS degradation. It is found that the volatile suspended sludge is decomposed into small molecular organic compounds, such as soluble protein, carbohydrate, short-chain fatty acids and ammonia by wet air oxidation, which improves the sludge dewater ability significantly.

Key words: waste water bio-treatment, excess sludge, wet air oxidation, volume reduction