Treating wastewater while protecting the climate

China’s unprecedented urbanisation in the 21st century came with a surge of municipal sewerage projects, which have been indispensable in ensuring sanitation facilities for the urban population. Over 97 per cent of urban wastewater in China is currently treated in municipal wastewater treatment plants (WWTPs) – a remarkable achievement in terms of environmental protection and public health.

Despite this, as decarbonisation takes on a more important role in every sector of Chinese society, wastewater treatment must also address its own carbon emissions. This poses an “existential” problem for the industry, as the removal of organic matter, along with nitrogen and phosphorus contents from wastewater ends up releasing methane, nitrous oxide, and carbon dioxide into the atmosphere. Greenhouse gas (GHG) emissions arising from WWTPs are estimated to account for between 1 to 2 per cent of China’s overall emissions.

On 29 December 2023, the National Development and Reform Commission (NDRC), the Ministry of Housing and Urban-Rural Development (MOHURD), and the Ministry of Ecology and Environment (MEE) jointly released a guideline on improving synergy between pollution reduction and decarbonisation in municipal wastewater treatment, based on which one hundred “demonstration plants” would be built by the end of 2025, with industry-leading performance in the circular economy and low GHG emissions.

One notable measure within the guideline requires local governments to set scientifically-based, reasonable targets for the quality of treated water discharged by WWTPs. This refers to a prevalent phenomenon in which WWTPs make excessive use of energy-intensive technologies or chemical substances in order to adhere to existing, overly ambitious governmental requirements, which results in unnecessary GHG emissions.

Meanwhile, the guideline encourages the adoption of smart, digital technologies and environmentally-friendly chemical substances in wastewater treatment. WWTPs are also advised to join the broader collective effort in optimising energy consumption and investing in renewable energies.

Looking forward, the latest call for reducing GHG emissions could create promising business opportunities for smaller enterprises that employ cutting-edge green technologies capable of solving individual problems for WWTPs.