1. Ph.D. Student, Dept. of Environmental Engineering, Egypt-Japan Univ. of Science and Technology, P.O. Box 179, New Borg Al-Arab City, 21934 Alexandria, Egypt (corresponding author).
2. Professor, Dept. of Environmental Engineering, Egypt-Japan Univ. of Science and Technology, P.O. Box 179, New Borg Al-Arab City, 21934 Alexandria, Egypt.
3. Associate Professor, Dept. of Civil Engineering, Tokyo Institute of Technology, 2-12-1-M1-4, Meguro-ku, Tokyo 152-8552, Japan.