1. Ph.D. Candidate, Division of Environmental Science and Engineering, National Univ. of Singapore.
2. Professor and Executive Director, Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological Univ., 50 Nanyang Ave., Block N1-B3b-29, Singapore 639798 (corresponding author).
3. Assistant Professor, Division of Environmental Science and Engineering, National Univ. of Singapore.