1. 1）Wei, Y., Van, H.R.T., Borger, A.R., Eickelboom, D.H., and Fan, Y.: Minimization of excess sludge production for biological waste water treatment. Water Res., 37(18), 4453－4467 (2003)
2. 2）Ide, T.: Water Treatment Engineering, Gihodo Shuppan, Tokyo, p.214 (1990) (in Japanese)
3. 3）Editors：Eckenfelder, W.W., and Grau, P.: Activated Sludge Process Design and Control: Theory and Practice,: Technomic Publishing Co.; Lancaster, (1998)
4. 4）Miyoshi, Y.: Ideas and Techniques of Sewage and Waste Water Treatment, Ohmsha, Tokyo, p.55－169 (2006) (in Japanese)
5. 5）Sawada, Y., Nagashima, S., Uchida, T., Kawashima, N., Takeuchi, S., Akita, M., and Nagaoka, H.: Basic study on sludge concentration and dehydration with ultrasonic exposure. Jpn. J. Appl. Phys., 44(6B), 4678－4681 (2005)