An expert committee has led development of an advanced sustainable wastewater treatment plant concept. Han-Qing Yu, Hongchen Wang and Jun Chen report on progress, including the first plants.
After nearly 40 years of remarkable development, China currently has the second-largest economy in the world. The country also now possesses the world’s largest municipal wastewater infrastructure asset base, but in which direction is this headed?
With thousands more wastewater treatment plants (WWTP) being planned for the near future, several distinguished professors specialising in wastewater treatment formed the China Concept WWTP Committee (CCWC) in 2014 and began to ponder the goals of wastewater management in 21st century China.
The CCWC concluded that future wastewater treatment plants should achieve four essential goals – sustainable water quality, resource recovery, energy neutrality, and environmental friendliness – brought together in what is known as the Concept WWTP. The China Concept WWTP is oriented to 2030-40, practising low-carbon concepts, and intensively applying and demonstrating global advanced technologies that have been and will be engineered so as to meet fully the requirements of China’s sustainable development strategy and with the hope of becoming the benchmark of municipal wastewater treatment plants in the world.
“What we care about is not the concept, but the future,” says Professor Jiuhui Qu, the leading member in the CCWC. “The future not only requires creativity, but also calls for actions, applying creativity to create a future without sewage and using actions to achieve a bright future full of wisdom.”
Over more than seven years, the CCWC has gathered global insights and cooperated with many domestic institutions. Discussion and exchanges, visits, collaborative research, formulation of plans, work on engineering practice, and gathering of feedback have been carried out. The committee has completed a preliminary round spanning concept, technology, and construction demonstration, right through to obtaining social feedback to provide the basis for the Concept WWTP.
The first Concept WWTP in China
The CCWC also promotes implementation of the Concept WWTP. The first plant to have been built around the concept is Sui County No.3 WWTP, which serves a population of about 900,000. This is in Sui County, Henan Province, in central China, approximately 700km south of Beijing and 800km northwest of Shanghai.
Surface water in the county is in short supply and of poor quality. The evaporation rate is high and it is common for groundwater to be overdrawn. The county also has an active livestock and poultry breeding industry. Small to medium size farms are scattered over the county. Inadequately managed manure forms non-point pollution sources, causing water pollution problems. Furthermore, the southeast section of the county has experienced rapid urbanisation in the early 2010s. A wastewater treatment plant was desperately needed to manage the increasing amount of sewage generated in this area and to prevent further degradation of local water quality. This proved to be an excellent opportunity to build the Sui County No.3 WWTP around the goals set out by the CCWC.
The project, which has a total budget of 180 million yuan (approximately $26 million), began construction in the second half of 2017, and the plant started operation in early 2019. A public-private-partnership (PPP) model was used for the plant construction. Through an open bidding process, the Sui County government selected CSD Water Service (CSDWS) as the private sector partner. The Henan Water Conservancy Investment Group Co., Ltd was the project lead. The project team also included the First Engineering Bureau of Henan Water Conservancy Co., Ltd. CSDWS was responsible for process design, technology and equipment supply, plant construction, and plant operations.
The Sui County No.3 WWTP is designed to treat an average flowrate of 40,000m3/day. In the first phase, the average design flowrate is 20,000m3/day. The plant includes a liquid treatment area, an organic waste processing area, a constructed wetland, agriculture and sponge city demonstration areas, and an office building and education centre.
Wastewater is treated by preliminary treatment (screens and aerated grit chamber), primary clarification and fermentation, and a step-feed activated sludge process with biological nutrient removal. Secondary effluent is polished by denitrification filters and disinfected by ozonation, which is also effective for destruction of trace levels of emerging contaminants. Treated effluent passes through a constructed wetland, replenishing local surface water bodies, but could be reused in industrial applications.
A wastewater treatment plant was desperately needed to manage the increasing amount of sewage
The organic waste processing system is designed to treat 100 tons/day. Sludge produced from wastewater treatment is co-digested with manure collected from livestock and poultry farms and straw from agricultural operations throughout the county. This uses the DANAS (Dry ANAerobic System) process, a dry anaerobic digestion technology developed by CSDWS. Design capacity for the first phase project is 50 tons/day. Co-digestion not only mitigates the non-point source pollution problems in the county, but also produced 510,000m3 of biogas, 438,765kWh of electricity and 4500 tons of fertiliser in 2020.
The constructed wetland, agricultural demonstration area (using the organic fertiliser produced on site), and sponge city demonstration area make up an ecological park that demonstrates the synergy between wastewater treatment and the surrounding environment. The office building houses a modern control centre and an exhibition hall that displays the treatment technologies employed at the plant. It also serves as an education centre to demonstrate the importance of environmental protection and how various resources can be recovered from wastewater and reused beneficially.
Wastewater as a resource
The Sui County No.3 WWTP serves as an example for future WWTP planning and design in China, promoting environmental and social sustainability. The high-quality effluent produced helps alleviate some of the water resources-related challenges facing the county. The processing of organic waste reduces non-point source pollution and produces compost that can be reused beneficially as an organic fertiliser. The recovered biogas is used to generate heat and power for plant operations. These aspects are connected in a material cycle (see diagram). Creation of the ecological park also helps promote this example.
Having adopted the goals set out by the CCWC, the Sui County No.3 WWTP project has received national recognition, with achievements including an energy self-sufficiency of 50% (see figure).
The Sui County No.3 WWTP has also attracted much interest from wastewater professionals throughout China. Several further treatment plants are already being constructed following the Concept WWTP model.
Yixing Wastewater Resource Concept Plant is another important Concept Plant planned by the CCWC. From the beginning of 2017 to the end of 2019, after five drafts were changed, the design was finally completed by the Beijing Municipal Institute, SUP Atelier and THUPDI Architectural Design Branch. Construction of this plant will be completed in early 2021. Yixing Concept Plant will not only become a water resource recovery facility, but also build a full-scale R&D centre aiming at comprehensive research and verification of forward-looking technologies.
In the future, after the Yixing Concept Plant goes into operation, the CCWC will strive to build approximately 100 Concept Plants in the coming five to eight years, applying advanced technologies and covering various local conditions, different capacities, distinctive features, and diverse models. These will promote substantial changes and upgrades in industry construction forms, technology, and standards.
Overall, after seven years of planning and practice, the idea of building a future-oriented wastewater concept plant has deeply affected the industry in China. Many water companies have shown great interest and strong demand for building Concept Plants. China National Development and Reform Commission has also recently issued guidelines on promoting the utilisation of wastewater as a resource, which will further promote Concept WWTP developments. Progress with China Concept WWTPs is expected to continue and they will reshape the wastewater treatment landscape in 21st century China. •
Han-Qing Yu is at CAS Key Laboratory of Urban Pollutant Conversion, University of Science & Technology of China, Hefei
Hongchen Wang is at School of Environment and Nature Resources, Renmin University of China, Beijing
Jun Chen is at CSD Water Service, Beijing