Towards the new era of water reuse in China
China has been expanding water reuse over the past few decades. Hong-Ying Hu, Zhuo Chen, Shuran Hao and Yinhu Wu chart the progress and look at prospects for the coming years.
In recent years, water reuse in China has experienced a booming development. Use of reclaimed water has been increasingly considered as a sustainable strategy that can save substantial freshwater consumption, reduce treated effluent discharge, and contribute to a lower carbon footprint and progress towards a circular economy.
The development of water reuse has gone through several stages in China. The first of these was from 1981 to 1985 (6th Five-Year Plan period), which represented the preliminary stage of water reuse in China. The prospect and feasibility of reusing treated effluent was examined during that period via pilot projects in the cities of Qingdao and Dalian. These initial efforts demonstrated that the reclaimed water could be used as a reliable water resource after appropriate treatment.
From 1985 to 2000, in the ‘boot stage’, a series of case studies was launched in northern China because of the implementation of national water pollution control policy. For instance, a great number of water reuse projects were demonstrated in the cities of Xi’an and Tianjin. Wastewater treatment and reuse technologies were evolved accordingly.
The rapid development stage started in 2000, resulting from the enforcement of relevant policies and provision of financial support. Water reuse became a long-term strategy in water resource management to meet the rising water conflict and demand in China. The wastewater treatment and reuse ratio in water deficient cities of northern China thus soared. This took the country towards the next development phase, which has seen growth at a steady pace since 2010, with more and more cities making overall planning in which water reuse projects were developed at local and regional scales.
The current situation
Today, water reclamation facilities have been implemented and constructed in China at a steady increasing trend. Centralised water reuse systems have been the dominant pattern in urban regions, with decentralised water reuse systems sporadically implemented in some individual buildings and rural areas. As shown in Figure 1, the total municipal water reuse quantity in China reached 12.62 billion m3 in 2019, of which more than 80% was applied for ecological, environmental, and industrial uses (e.g., cooling-water, processing, and boiler feed water), followed by agricultural irrigation, urban miscellaneous uses (e.g., toilet flushing, gardening, car washing, and firefighting). Examples of reclaimed water applied for environmental applications are given in the photo above and on page 21. The length of pipelines constructed for reclaimed water uses has also increased rapidly, exceeding 15,000km by the end of 2019.
The water reuse rate achieved in urban areas of China has reached a relatively low level, at around 19.9%. Meanwhile, the quantity of wastewater discharged in urban areas of China is considerable, with an annual volume of 65.7 billion m3 in 2019, of which nearly 96.3% (63.3 billion m3) was treated.
Recently, the 14th Five-Year Plan (2021-25) proposed that, during this five-year period, the construction of reclamation facilities will be strengthened and the utilisation of sewage resources will be promoted. The newly constructed, rebuilt and expanded production capacity of reclaimed water shall not be less than 15 million m3 per day. Consequently, there is still great potential to further expand water reuse in terms of quantity and of applications. The key factors influencing the evolution and progress of water reuse in different places have been identified as the local water scarcity situation and the level of economic development (Figure 2).
In the past, compared with other public utility services, reclaimed water reuse projects have shown relatively low profit because of the upfront investment in facilities and lack of potential customers. So, the main investors were central and local government. In recent years, the Chinese government has increased the investment budget supporting reclaimed water projects and companies. According to the 13th Five-year Plan (2016-20) on construction of urban sewage treatment and recycling facilities, $88bn (CNY564.4bn) was planned to be invested in the development of urban wastewater treatment and reuse facilities. China’s annual investment in fixed assets for urban wastewater treatment and reclaimed water reached $16.28bn (CNY104.2bn) in 2019.
Standards and guidance
Government has inevitably played an important role in promoting the utilisation of reclaimed water in China. Previously, in early 1986, urban wastewater reuse was an issue on the national scientific and technological priority list. Subsequently, safety and efficiency of water reuse was emphasised during the 10th Five Year Plan period (2001-05). A series of national standards on water quality requirements for different reclaimed water applications and water reuse design codes have been enacted since 2002. The ever-stringent reclaimed water quality requirements also call for the evolution of treatment technologies. The activated sludge process used to be one of the commonly adopted methods in secondary treatment. Subsequently, because of concerns about eutrophication, denitrification processes were adopted. In the past 15 years, advanced treatment technologies, such as membrane bioreactors, membrane filtration (e.g., microfiltration, ultrafiltration and reverse osmosis) and disinfection (e.g., use of chlorine, ozone and ultraviolet irradiation) have been increasingly employed to produce high-quality reclaimed water.
Recently, with approval by the China State Council, an official document entitled Guidance document on promoting wastewater resource utilisation was jointly issued by the China National Development and Reform Commission (NDRC), and nine other national Ministries, on 11 January 2021. Based on the document, China will vigorously improve wastewater reclamation, reuse and resource utilisation at the national level. The Guiding Document aims to further promote and speed up wastewater resource utilisation systematically in domestic, industrial, ecological, and agricultural applications. Water deficient and water sensitive regions are targeted as key areas, and the establishing of pilot demonstration cities is encouraged.
The overall target is to achieve water reuse rates of more than 25% in water deficient cities, with more than 35% in the Beijing-Tianjin-Hebei region of China by the year 2025. The corresponding market, as well as policies and guidelines on wastewater treatment and reuse, will be formed. It is anticipated that, by 2025, a systematic, safe, environmentally friendly, economically feasible and efficient pattern of wastewater resource utilisation will be established. Given this, wastewater reclamation, reuse and resource utilisation will have bright and broad prospects in China in the near future.
Even so, for long-term sustainable practices of water reuse, continuous research and development is essential. The concepts of ‘fit for purpose’ and ‘fit for case’ were proposed to encourage water reuse in an economically feasible manner. ‘Fit for purpose’ describes the treatment of reclaimed water to a quality that meets the needs of the intended water reuse applications. ‘Fit for case’ highlights the need to consider case-specific conditions (i.e., different situations and characteristics) during water reuse. The corresponding Chinese national standards regarding reclaimed water classification and water quality requirements for different applications can be followed. These can improve the overall appeal of reclaimed water, by making it economically feasible in treatment and reclamation, and adaptive to the end uses. Simultaneously, guidelines, standards, regulations and policies are significant when conducting water reuse planning, design, construction, operation, management and end use applications. •
Qu, J. et al., Municipal wastewater treatment in China: development history and future perspectives, Front. Environ. Sci. Eng. 2019, 13 (6), 88.
Ministry of Housing and Urban-Rural Construction of the People’s Republic of China (MOHURC), National municipal wastewater treatment management system, Ministry of Housing and Urban-Rural Construction of the People’s Republic of China, Beijing, China, 2019.
Xu, A. et al., Towards the new era of wastewater treatment of China: development history, current status, and future directions, Water Cycle. 2020, 1, 80–87.
Chen, Z. et al., Centralised water reuse system with multiple applications in urban areas: lessons from China’s experience, Resour. Conserv. Recycl. 2017, 117, 125–136.
Professor Hong-Ying Hu, Dr Zhuo Chen, Ms Shuran Hao and Associate Professor Yinhu Wu are at the School of Environment, Tsinghua University, Beijing, PR China.
Beijing city case study
Beijing represents a typical metropolitan city in northern China, with a population of 21.9 million. At the same time, the water resources are nearly the lowest per capita in the world (114.2 m3 per capita per year), with a heavy reliance on groundwater extraction. With continuous expansion of urbanisation and growth of population, the conflicts between conventional water supply and water demand have become more apparent. Therefore, Beijing has been vigorously promoting the long-distance water diversion from southern cities, as well as the utilisation of reclaimed water to alleviate the shortage of water.
In 2019, the amount of reclaimed water use in Beijing was 1.15 billion m3, accounting for 27.6% of the city’s total water supply, and the water reuse rate has reached 58.2%. Most reclaimed water is applied for ecological and scenic environment uses, such as the supplementing of environmental flows in lakes and river channels within the city, which has greatly improved the urban landscape and ecological environment. In addition, some reclaimed water is used for industrial applications, such as cooling, boiler feed and industrial processing.
In 2020, the reclaimed water use quantity for industrial applications in Beijing was 5.8 million m3. Some high-tech companies in the Beijing Economic-Technological Development Area are using reclaimed water as important water sources for producing highly purified water (above).