In order to clarify the mechanism of the drying-rate increase and stinky odor reduction of hydrothermal treated sewage sludge with rice husk by steam at 473K and 1.8MPa, the drying characteristic and the stinky odor ingredient concentration were measured and analyzed about three substances, the raw sewage sludge, treated sewage sludge and treated sewage sludge with rice husk, Their mechanism was considered. In the drying-rate characteristic, it turned out that the constant-drying-rate of treated sewage sludge with rice husk were higher than without rice husk. It turned out that the falling-drying-rate of treated sewage sludge was higher than raw sewage sludge. From these results, to mix rice husk has an effect to increase constant-drying-rate, and hydrothermal treatment has an effect on falling-drying-rate. By mixing rice husk, sewage sludge was adhered on the surface of rice husk and distributed. Therefore, one of the reasons of the constant-drying-rate increase is considered that the specific surface area per weight was increased. Furthermore, one of the reasons of the falling-drying-rate increase is considered that hydrothermal treatment changed chemical characteristic of raw sewage sludge. On the other hand, in the odor characteristics, it turned out that about 10% of the sulfur moved from solid to condensed liquid and gas by hydrothermal treatment. One of the mechanisms of stinky odor reduction is concerned the sulfur content in raw sludge decreased by hydrothermal treatment. Moreover, organic acids concentrations increased by hydrothermal treatment. From the results, another mechanisms of that is concerned the concentration of sulfur compounds decreased due to the concentrations of organic acids became high.
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