1. a Department of Municipal Engineering , Southeast University , Nanjing, P. R. China
2. b Croucher Institute for Environmental Sciences, and Department of Biology , Hong Kong Baptist University , Kowloon Tong, Hong Kong, P. R. China
3. c State Key Laboratory of Pollution Control and Resource Reuse Research, School of Environment , Nanjing University , Nanjing, P. R. China
4. d Department of Biology and Chemistry , City University of Hong Kong , Kowloon Tong, Hong Kong, P. R. China