Sun Shuiyu

Effect of low power ultrasound on aerobic/anoxic digestion of activated sludge.

The effect of low power ultrasound on aerobic/anoxic digestion of activated sludge was investigated. First, dehydrogenate activity (DHA) and special oxygen uptake rate (SOUR) were detected to indicate the change of biological activity of sludge induced by ultrasound. Single-factor experiments showed that when the ultrasonic frequency was 28 kHz, the optimal ultrasonic density and exposure time were 0.15 W/mL and 10 min, respectively. Through orthogonal tests, the optimal ultrasonic parameters for aerobic/anoxic digestion were found to be a ultrasonic density of 0.15 W/mL, ultrasonic exposure time of 10 min and interval time of 12 h. The aerobic/anoxic digestion was improved by ultrasonic pretreatment, the VSS reduction at the optimal conditions was increased by 35.73%, compared with the control. It can be concluded that low power ultrasonic pretreatment is a valid method for improving aerobic/anoxic biodegradability of activated sludge.

Study on Industrial Sludge Catalytic Combustion by TGA

It is necessary to clarify the combustion process of industrial sludge in order to utilize it efficiently as an energy source. In this paper the influences of three catalysts (K2CO3, NaCl and Al2O3) on the ignition and burn off characteristics of industrial sludge had been investigated by simultaneous thermogravimetric analysis (TGA) with linearly increasing temperature at air atmosphere. The results indicated that the metallic compounds had some catalytic effects on the combustion of industrial sludge. The ignition temperature dropped in the presence of K2CO3, NaCl and Al2O3 and three catalysts were all favorable for the combustion of industrial sludge. Furthermore, characteristic indexes of combustion were changed a degree correspondence to add different metals. While to the same metal, the catalytic action was also variant at different combustion stages. But in the whole process the catalytic action of K2CO3 performed stronger than that of NaCl and Al2O3 .The catalytic mechanism of industrial sludge combustion was distinct with adding different metal compounds. The ignition point was ahead at the beginning of combustion because the organic volatile compounds were released stimulatively with the domination of metal compounds. But at the other stages, metals serving as the carrier of oxygen made it easier for sludge combustion with the displacing and diffusing of oxygen.