Safeguarding water resources in the upper-middle Yangtze River
Situated in the Three Gorges Reservoir region, Chongqing is China’s most populous municipality. Ensuring high-quality wastewater treatment for over 10 million residents while protecting the Yangtze River resources presents a significant challenge. In response, Chongqing enforces strict effluent discharge standards, strengthening its role as an upstream ecological barrier.
Our solution
A WWTP with integrated processes and cutting-edge technologies
The Chongqing Tangjiatuo WWTP, invested in and operated by SUEZ, employs the advanced A-AO biological wastewater treatment process, sludge digestion and dewatering, and the Evaporis™ 2E two-stage sludge drying process. It is equipped with systems for resource recovery, including tailwater power generation and water reuse. As one of China’s largest and most advanced WWTPs, Tangjiatuo WWTP plays a pivotal role in protecting the water quality and ecological balance of the upper-middle reaches of the Yangtze River while enhancing Chongqing’s appeal as an investment destination.
The WWTP currently treats 400,000 m3 of wastewater and 320 tons of sludge daily, serving 1.37 million residents. To enhance capacity and mitigate overflow risks during rainy seasons, we launched an expansion project in December 2024. Covering 9.2 hectares, Phase IV is set for completion by December 2026, boasting the total treatment capacity to 600,000 m3 per day.
The expanded WWTP will integrate green technologies and low-carbon, energy-efficient processes that optimise carbon recycling and maximise energy efficiency. By incorporating water reuse and solar power generation, the plant will efficiently utilise resources and generate green electricity to support sustainable operations. Furthermore, the WWTP will leverage digital twin technology to enhance process intelligence, reduce costs, and improve efficiency.
Harmless sludge disposal and resource recovery
As early as 2009, the WWTP built and has operated SUEZ’s largest sludge drying production line worldwide at the time by using its patented technologies, Innodry® 2E solution, to transform sludge into valuable resources. Additionally, the plant uses the Group’s Evaporis™ 2E two-stage sludge drying process to reduce sludge water content from 75% to 20% after digestion and dewatering. The dried sludge is transported to a local cement plant in Chongqing, where it is co-combusted with coal, enabling safe sludge disposal and resource recovery.
The results
- The WWTP solution achieves 20%-25% energy self-sufficiency through tailwater power generation and biogas reuse. It also recycles water through the reclaimed water reuse system, significantly reducing the consumption of natural gas, electricity, and raw water, saving 4 million m3 of natural gas, 5 million kWh of electricity, and 4 million m3 of water annually.
- The WWTP pioneered a locally adapted disposal route: medium-temperature anaerobic digestion + centrifugal dehydration + two-stage thermal drying. This process addresses Chongqing’s sludge disposal challenges while providing a scalable model for other cities.
- Selected as a national benchmark WWTP for operations management and precision control of key processes.
- Awarded the IWA Climate Smart Utilities recognition.
- Recognised as a green and low-carbon model project in Chongqing in 2024.
energy self-sufficiency rate through tailwater power generation and biogas reuse