1. College of Environmental Science and Engineering, Hunan University, Changsha 410082, P. R. China
2. Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082, P. R. China
3. Hunan Qing Zhi Yuan Environmental Protection Technology Co., Ltd., Changsha 410004, P. R. China
4. Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, NSW 2007, Australia