1. R&D Engineer, Infilco Degremont Inc., North American Research and Development Center, Richmond, VA 23219; formerly, Ph.D. Student, Dept. of Civil and Environmental Engineering, Duke Univ., Durham, NC 27708.
2. Process Development Team Manager, Metropolitan Water District of Southern California, 700 Moreno Ave., La Verne, CA 91750.
3. Associate Professor, Dept. of Civil and Environmental Engineering, Duke Univ., Durham, NC 27708 (corresponding author).