【Ecological Focus】
Author: Zhang Wenjing (Researcher, Chinese Academy of Environmental Planning, Ministry of Ecology and Environment)
On May 1, 2024, the Water Conservation Regulations (hereinafter referred to as the "Regulations") will come into force. The "Regulations" stipulate that the local people's governments at or above the county level shall make overall plans and construction of infrastructure for the utilization of sewage resources and promote the utilization of sewage resources. The per capita water resources in mainland China are scarce, the spatial and temporal distribution is uneven, and the problem of resource-based and water-quality water shortage still exists, and the regional reclaimed water recycling is a new way to realize the "three-water integration" (water resources, water environment, and water ecology) system governance.
Spring flowers are blooming, and visitors are playing in Kunming Baofeng Wetland Park. Xinhua News Agency
Ning'an Road Primary School in Qingdao City, Shandong Province carried out the theme activity of "Dripping Water at the Fingertips and Saving Water in the Heart", and students were doing small experiments on sewage purification. Xinhua News Agency
Spring landscape of Lixiahe National Wetland Park, Xinghua City, Jiangsu Province Xinhua News Agency
In recent years, the continent has achieved a profound change in the use of water resources, from extensive and inefficient to economical and intensive, with 6% of the world's freshwater resources to feed nearly 20% of the world's population and create more than 18% of the world's total economic output. However, the per capita water resources on the mainland are scarce, the spatial and temporal distribution is uneven, and the problem of resource-based and water-quality water shortage still exists. In order to break through the bottleneck, some regions have innovated and carried out regional reclaimed water recycling, which not only improves the water ecological environment, but also alleviates the contradiction between supply and demand of water resources, and explores a comprehensive treatment model that organically combines pollution control, ecological protection and recycling.
What is regional reclaimed water recycling
The so-called regional reclaimed water recycling is to build engineering facilities such as water purification of constructed wetlands according to local conditions at key nodes such as the downstream of key sewage outlets, river estuaries (sea) estua, and tributaries flowing into the main stream.
Compared with the traditional point-to-point reclaimed water utilization mode, regional reclaimed water recycling has two advantages: first, the ecological purification facilities such as artificial wetlands endow the reclaimed water with natural attributes, so that the reclaimed water becomes "ecological water", which improves the public's acceptance of reclaimed water, and is conducive to the use of reclaimed water for ecology and life;
In the four lakes basin in the southeast of Shandong, the local ecological environment, water conservancy and other departments have worked together to fully consider the amount of reclaimed water generated, utilized, the amount of water that can be accepted by the constructed wetland, the storage capacity of the basin, the hydrometeorological conditions and other factors, and 21 million cubic meters of reclaimed water have been built in various cities in the basin, and 210 million cubic meters of reclaimed water are widely used in urban sprinkling and dust suppression, power plant operations, farmland irrigation, etc. At the same time, since the opening of the eastern route of the South-to-North Water Diversion Project, the water quality of Nansi Lake has been stable and better than the Class III standard of surface water, and the water quality safety has been effectively guaranteed.
Why do we need to implement regional reclaimed water recycling?
Regional reclaimed water recycling is a new way to realize the "three water integration" (water resources, water environment, and water ecology) system governance.
First, the overall promotion of reclaimed water recycling from the regional level can realize the diversified utilization of reclaimed water, improve the efficiency of water resource utilization, and solve the problem of "grabbing" surface water and "crowding" ecological water for industrial water, agricultural water and urban water supply. As a key link in the regional reclaimed water recycling, the constructed wetland can not only play a natural purification function, reduce the pollution load of the water body, and continuously improve the water quality of the water body, but also play the role of ecological regulation and control, optimize the structure of the water ecosystem, improve the coverage of aquatic plants, and promote the realization of the goal of having rivers and water, fish and grass, and harmony between people and water. At the same time, the constructed wetland itself is also an important ecological landscape, which creates good conditions for the construction of a green space in harmony between man and water. For example, the Xinfeng River Basin in Beijing has achieved an annual water replenishment of more than 46 million tons through the improvement of artificial wetland quality and ecological supply of reclaimed water, ensuring the ecological base flow of the river, and the river has developed from a single lotus variety to 28 species of aquatic plants, and the vegetation coverage has increased from 10% to 40%, and the types and numbers of fish and birds have gradually increased, and the comprehensive index of water ecological health has reached the "healthy" level.
Second, regional reclaimed water recycling is conducive to promoting the synergy of pollution reduction and carbon reduction. Generally, the pollution control process is an energy-consuming process, such as the operation of sewage treatment plant equipment and the dosing of chemicals, which will increase carbon emissions. Compared with traditional in-depth sewage treatment, it can remove pollutants such as nitrogen and phosphorus, play a role in improving water quality, and can also reduce the energy consumption and drug consumption of advanced sewage treatment, thereby reducing carbon emissions. In addition, the implementation of regional reclaimed water recycling can also reduce the demand for water transfer outside the region, and indirectly reduce the carbon emissions caused by remote water transfer.
Third, regional reclaimed water recycling is an important measure to promote the coordinated development of ecological environmental protection and economy and society. The good ecosystem created by the constructed wetland water purification project contains considerable economic value, which can drive the development of surrounding ecological planting and breeding, cultural tourism, Internet marketing and other industries, promote ecological protection and restoration, environmental governance, and area development, realize the overall premium and value-added of the region, and form a new pattern of mutual promotion between ecological construction and economic development. In this regard, Jining City, Shandong Province, has built Weishan Lake into a hotspot and boutique for wetland eco-tourism, and the integration and development of e-commerce and Weishan Lake's characteristic industries has accelerated, with e-commerce retail sales reaching 720 million yuan in 2021.
How to implement regional reclaimed water recycling
In an area, the production, utilization, and storage of reclaimed water, including the purification capacity of the water cycle in the constructed wetland, must be matched, otherwise it will cause inconsistencies and may cause engineering problems. In order to ensure that the regional reclaimed water recycling can give full play to the benefits, it is necessary to fully grasp three key links in the implementation process.
The first is to strengthen source control and avoid toxic and harmful substances from entering the regional reclaimed water recycling system. About 1/5 of the urban sewage treatment plants in the mainland have accepted industrial wastewater, which may contain toxic and harmful substances, which are difficult to effectively remove, once recycled into the field of life and ecology, the health and ecological risks are greater, and the current reclaimed water safety management foundation is weak, so it is necessary to properly solve the risk prevention problem, standardize the selection of sewage water sources, and provide a reliable guarantee for the regional reclaimed water recycling.
Second, the constructed wetland water purification project is not a treatment unit of a sewage treatment plant. It is the responsibility and obligation of the sewage treatment plant to achieve stable discharge standards, and the positioning of the constructed wetland is ecological purification, which only undertakes the task of improving water quality, not the task of pollution control, and cannot use the constructed wetland to discharge sewage beyond the standard.
Third, when making full use of natural endowments such as rivers and reservoirs to build a regional reclaimed water recycling system, it is necessary to fully consider external influences such as natural force majeure. In the process of regional reclaimed water recycling, the production, storage, transmission and distribution of reclaimed water, and the utilization of reclaimed water, the reduction of the storage and transportation capacity of rivers and reservoirs in the flood season, and the reduction of the degradation efficiency of pollutants in constructed wetlands under low temperature conditions are all key issues affecting the smooth operation of the whole system, which must be considered in advance in the design process.
To sum up, the regional reclaimed water recycling is of great significance, and involves all aspects and multiple fields, which needs to be studied from the three dimensions of technology, economy and management, grasp its laws, and form a complete framework system, so as to provide support and services for top-level design and grassroots exploration.
Guangming Daily (2024-04-06 08 edition)
Source: Guangming Net-Guangming Daily