1. Research Center for Environmental Quality Control, Kyoto University, 1-2 Yumihama, Otsu City, Shiga 520-0811, Japan, Department of Civil Engineering, University of Illinois at Urbana−Champaign, 1101 West Peabody Drive, Urbana, Illinois 61801-4723, and Takuma Co. Ltd, Sewerage Engineering Department, 2-33, Kinrakuji-cho 2-chome, Amagasaki, Hyogo 660-0806, Japan