1. State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210023, P. R. China
2. Department of Civil and Environmental Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
3. Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan