1. Department of Environmental Engineering, Middle East Technical University, Inönü Bulvari, 06531, Ankara, Turkey
2. Department of Environmental Engineering, Middle East Technical University, Inönü Bulvari, 06531, Ankara, Turkey. Phone: +90-312-210 58 67; Fax: +90-312 210 26 46; E-mail: goksel@metu.edu.tr