Qun-hui Wang*, Kohji Kakimoto*, Hiroaki I. Ogawa*, Kazuhiro Fujisaki* and Yasuhiko Kazuhiro*

* Division of Material Sciences and Engineering, Faculty of Engineering, Kyushu Institute of Technology

+ Correspondence should be addressed to Yasuhiko Kato:
(Sensui 1-1, Tobata, Kitakyushu, Fukuoka 804 Japan)

Abstract

The conditions for enhancing the efficiency of an anaerobic digestion process were examined with waste activated sludge pretreated by ultrasonic disintegration, thermal treatments and freezing. The organic particulates in waste activated sludge were solubilized to soluble proteins and carbohydrates and other substances by various pretreatments. There is a clear correlation between the solubilization efficiency of waste activated sludge and the methane production. Ultrasonic pretreatment for 30 minutes resulted in a more than 60 percent increase in methane generation. The thermal pretreatment at a relatively low temperature can be expected to enhance the methane production with limited waste energy. In addition, the effects of the mixture ratios of waste activated sludge by various pretreatment and digested sludge on the anaerobic digestion process were also examined.

Key words: waste activated sludge, pretreatment, solubilization, anaerobic digestion