His research focuses on biological processes and advanced environmental biotechnology for wastewater reclamation, with particular emphasis on:
- Energy-neutral/positive wastewater reclamation technology.
- Energy and resource recovery from biosolids.
- Membrane bioreactors (MBR) and related technologies.
Dr. Liu's research has been widely recognized, with over 200 papers garnering more than 9,000 citations and an h-index of 53. He has also authored and edited seven technical books published by leading publishers such as Elsevier, Wiley, and CRC Press. In recognition of his contributions to research and public service, Prof. Liu has received several prestigious awards, including the Public Administration Medal (Bronze) in 2014, the Minister for National Development R&D Merit Award in 2013, and the Singapore National Technology Award in 2003.