1. Water Research Center, Korea Institute of Science and Technology, Seoul 136-791, Korea
2. Department of Chemistry, Rice University, Houston, Texas 77005, United States
3. Department of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, Korea
4. Department of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
5. Department of Civil and Environmental Engineering, Rice University, Houston, Texas 77005, United States