Enhancement of sludge gravitational thickening with weak ultrasound

作     者：Panyue ZHANG Tian WAN Guangming ZHANG 

作者机构：School of Environment Science and EngineeringHunan UniversityChangsha 410082China State Key Laboratory of Urban Water Resource and EnvironmentHarbin Institute of TechnologyHarbin 150090China 

出 版 物：《Frontiers of Environmental Science & Engineering》 (环境科学与工程前沿（英文）)

年 卷 期：2012年第6卷第5期

页      面：753-760页

核心收录：

学科分类：083002[工学-环境工程] 0830[工学-环境科学与工程（可授工学、理学、农学学位）] 08[工学] 0806[工学-冶金工程] 080601[工学-冶金物理化学] 

基　　金：supports from Furong Scholar Plan of Hunan Province  China and the State Key Laboratory of Urban Water Resource and Environment 

主　　题：activated sludge sonication settlability dryweight extracellular polymeric substances polyelectrolyte 

摘      要：Gravitational thickening is the prevailing method to reduce sludge volume but the process is slow and usually requires addition of polyelectrolyte（s）. This paper investigated the potential benefits of sonication on enhancing the sludge gravitational thickening with very low energy dose, so called ＂weak ultrasound＂. Results showed that weak sonication significantly changed the sludge settlability and the main mechanism was release of the loosely bounded extracellular polymeric substances. The changes in sludge behaviors by sonication were strongly influenced by power density and sonication duration. Lower sound frequency was slightly better than higher frequency. Weak sonication （ 〈 680 ***1 DS） improved the sludge gravitational thickening while high ultrasonic energy deteriorated the process. Considering both the sludge thickening efficiency and energy con- sumption the optimum conditions were 0.15 W. mL-l, 7 s, and 25 kHz. Under such conditions, the energy dose was only 155 ***-1 DS, much lower than literature reports, and the sludge settling time was shortened from 24 h to 12 h. Weak sonication could substitute expensive poly- electrolyte coagulant for sludge thickening. Combination of weak sonication and polyelectrolyte could further reduce the settling time to 6 h. The final water content of the thickened sludge was not changed after sonication or polyelectrolyte addition.