污泥膨胀和大量的剩余污泥是当前城市污水处理厂面临的重要问题.采用20kHz超声波,在不同的声能密度和超声时间下处理微膨胀活性污泥,研究低能量密度超声波处理对活性污泥的沉降性能及污泥减量的影响.结果表明:超声波处理可改善污泥沉降性能和实现污泥减量.适宜的超声处理时间为30~40s.超声处理后,泥水界面沉降速率可提高52%,污泥容积指数(SVI)可由202.9mL/g下降到151mL/g左右,污泥减量率为12.5%.在超声波处理40s时污泥减少已基本完成,而上清液的溶解性化学需氧量(SCOD)在40s之后还在大幅升高,从絮体中释放出来的污泥的溶解液化相对滞后.在一定范围内增加超声处理时间和提高超声能量密度有利于污泥减量效果的提升.活性污泥的初始pH对超声处理效果的影响不大.污泥初始浓度对污泥减量效果影响较大,采用超声波处理较高浓度的污泥时,污泥上清液SCOD增加值在25~29mg/gSS之间.%Sludge bulking and large amounts of excess sludge are the significant challenges for municipal wastewater treatment plant. The bulking activated sludge was treated by low intensity ultrasound with different ultrasonic densities and ultrasonic times under 20kHz. Effects of ultrasonication on the sludge settleability and sludge reduction were investigated. Results showed that the settleability of bulking sludge was improved by ultrasonication,and sludge reduction could also be achieved simultaneously. The desirable ultrasonic time was 30—40s. After ultrasonic treatment,the settle velocity of bulking sludge was increased by 52%,and its sludge volume index(SVI)was decreased from 209mL/g to 151mL/g. The sludge reduction rate amounted to 12.5%. With the 40s ultrasonication,sludge reduction was almost accomplished,while the soluble chemical oxygendemand (SCOD)concentration in the supernatant was still significantly increased. So the sludge solubilization was lagged behind its release from sludge floc. The increase of ultrasonic time and ultrasonic density within a certain range could improve the sludge reduction rate. There were little effects of initial pH of sludge on the results of ultrasonication. But the sludge reduction rate was significantly affected by initial sludge concentration. When the sludge with relatively high sludge concentration was ultrasonicated,the increase of SCOD in the supernatant amounted to 25—29mg/gSS.
展开▼
