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Sustainable wastewater treatment – ways to achieve energy neutrality

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.