Sustainable wastewater treatment – ways to achieve energy neutrality

Abstract

Increasing emission of greenhouse gases intensifies global warming. To tackle the problem, major economies in the world need to implement policy on energy saving. The wastewater treatment industry, being one of the energy consumers, has developed various technologies to improve energy efficiency and has started to use renewable energy with the aim of achieving energy neutrality in the wastewater treatment process. A literature review found that there is a series of energy-saving methods that can reduce the electricity consumption by 20% in wastewater treatment. Majority of the energy saving comes from energy conservation measures in pumping and aeration systems. In wastewater treatment works, two kinds of renewable energy are usually available, namely solar energy and biogas. The recent development of photovoltaic cells makes it a more practical and financially viable energy source which may cover 40% of the electricity consumption of a wastewater treatment works. Biogas, a by-product generated from the anaerobic digestion process in a wastewater treatment works, can also generate 40% of the electricity required. To achieve energy neutrality, the remaining electricity consumption can be generated through co-digestion of wastewater sludge and organic fraction in municipal solid waste.

Keywords:

• sustainable development
• wastewater treatment
• energy neutrality
• energy saving
• energy recovery
• anaerobic digestion
• co-digestion
• sludge pre-treatment

Acknowledgments

First of all, the authors would like to take this opportunity to express their sincere thanks to the Drainage Services Department, the HKSAR Government for participation in this paper. The first author is thankful to the co-authors, Ir W. C. FUNG and Ir K. K. CHEUNG, for their kind support provided during the course of this work.

Additional information

Miss Sze Wing Ho obtained a Bachelor of Engineering (Honours) degree in Mechanical Engineering from The University of Hong Kong. She is pursuing a Master of Science degree in Energy Engineering from The University of Hong Kong and is under direct objective training in the Drainage Services Department of the HKSAR Government. She obtained the award of best engineering graduate 2014 in the Electrical and Mechanical Service Department, the HKSAR Government.

Ir Kin Kuen Cheung is a Mechanical Engineer by profession. He obtained a Bachelor of Engineering (Honours) degree in Mechanical Engineering, and a Master of Science degree in Mechanical Engineering from the Hong Kong University of Science and Technology. He has been working with the Drainage Services Department, the HKSAR Government in the research and development team for wastewater treatment for 14 years.

Ir Wing Cheong Fung is a Mechanical Engineer by profession. He obtained a Bachelor of Engineering (Honours) degree in Mechanical Engineering from the University of Sheffield, and a Master of Science degree in Environmental Management from The University of Hong Kong. He has been working with the Drainage Services Department, the HKSAR Government in different divisions for 20 years and is now leading a research and development team for wastewater treatment.