1. State Key Lab. of Pollution Control & Resource Reuse, Tongji University, 1239 Siping Road, 200092 Shanghai, China (E-mail: tlj_tang@hotmail.com)
2. School of Municipal and Environmental Engineering, Harbin Institute of Technology, 202 Huanghe Road, 150090 Harbin, China (E-mail: cuifuyi@public.hr.hl.cn)