1. Department of Environmental Engineering, Democritus University of Thrace, GR 671 00, Xanthi, Greece.
2. Department of Environmental Engineering, Democritus University of Thrace, GR 671 00, Xanthi, Greece. Phone: +30 2541079377; Fax: +30 2541079376; E-mail: voudrias@env.duth.gr