How Underground Wastewater Treatment Plants Contribute to China’s Sustainable Urbanization?
How Underground Wastewater Treatment Plants Contribute to China's Sustainable Urbanization?
Rapid economic expansion, increasing population, and urbanization in China have caused an increase in urban wastewater discharge, and the shortage of urban land resources, which made the underground wastewater treatment plants increasingly urgent. By 2020, China's urban wastewater discharge has reached 57.14 billion cubic meters. According to the "2020 Urban and Rural Construction Statistical Yearbook" of the Ministry of Housing and Urban-Rural Development, as of 2020, there were 2,618 urban wastewater treatment plants in the country, with an annual wastewater treatment capacity of 55.73 billion cubic meters. The urban wastewater treatment rate was 97.53%, and the centralized treatment rate of urban wastewater treatment plants was 95.78%.
Current application of the underground wastewater treatment plants
On July 31, 2022, the first underground MBR wastewater treatment plant project in Shanghai is completed. After the plant has been put into operation, the daily wastewater treatment capacity reaches 150,000 tons, further improving Shanghai's water resources treatment capacity.
On December 31, 2021, the first underground wastewater treatment plant in Huaihai Economic Zone and the largest underground wastewater treatment plant in Jiangsu Province officially start operating.
On December 27, 2021, the reconstruction and expansion project of the Lanzhou Qilihe Anning Wastewater Treatment Plant officially starts. After the project has been completed, it will become the largest underground MBR wastewater treatment plant in Northwest China.
The wastewater treatment plant is located underground, and the park is on the ground level. The green lawns and patchwork vegetation defy the concept we usually have of odorous and noisy wastewater treatment plants. Consequently, this type of environmentally friendly underground wastewater treatment plant with a smaller area and no odor or noise pollution has gradually attracted people's attention.
Development trend of underground wastewater treatment plants around the world
The underground wastewater treatment plants originated in Finland. It is said that the Finns began to build them in 1932. Originally, underground wastewater treatment plants were built to save space. Traditional above-ground wastewater treatment plants take up a lot more space and urban land. Therefore, underground wastewater treatment plants can make urban planning easier. Furthermore, the geology of caves in Finland is also suitable for underground construction. The main treatment structures of the Viikinmäki Central Sewage Treatment Plant, the largest underground sewage treatment plant in Finland and the whole of Northern Europe, are built in caves. Sweden's first underground wastewater treatment plant was built in the 1950s, but the UWTP failed to develop further due to geological and technical conditions.
Since the 1970s and 1980s, in Finland, Sweden, Norway, Japan, and other countries, with superior geological conditions and advanced excavation technologies, a certain number of UWTPs have been built. In some big cities in the Netherlands, South Korea, England, Singapore, Malaysia, etc., many UWTPs have also been established, alleviating urban land occupation and environmental pollution problems.
China has only recently introduced underground wastewater treatment plants, but things move pretty fast: from 2010 to 2019, more than 30 UWTPs were put into operation, and some UWTPs are under construction. The first fully underground wastewater treatment plant in China, Shenzhen Buji Wastewater Treatment Plant, was completed and put into operation in 2011. As of the end of 2021, there were nearly 200 underground wastewater plants under construction across the country, of which Guangdong, Sichuan, and Guizhou are the top three.
Rapid urbanization took a toll on land resources, so underground wastewater treatment plants come as a solution for wastewater treatment because they save up space. From the perspective of environmental protection, underground wastewater treatment plants operate stably and are less affected by the external environment. The main structures are built below the ground. Through system design, secondary pollution such as odor and noise can be effectively isolated.
From an economic point of view, underground wastewater treatment plants are compact in layout and occupy a smaller area. The ground area can be used for other purposes, such as parks public facilities, stadiums, and parking lots, to name a few. E.g., 6 underground wastewater plants in Erhai (Dali) save about 160 mu of land compared to the original plan; the underground wastewater plant in Tianfu saves 360 mu of land, saving space for a park, and Tianfu West China Hospital, among other public facilities.
Another great example is the underground wastewater treatment plant at the Qicai Lake in Guiyang, (Guizhou) above which the ground has been transformed into an ecological park, and the treated wastewater is used for ecological replenishment of the park. The energy generated by the water source heat pump can also be used to heat the surrounding communities and office facilities.