Technical guide for water purification of constructed wetlands



A few days ago, the Ministry of Ecology and Environment issued the "Technical Guide for Water Purification of Constructed Wetlands" (hereinafter referred to as the "Guide"), which is used to guide the relevant work of water purification of constructed wetlands. Relevant responsible comrades of the Department of Water Ecology and Environment of the Ministry of Ecology and Environment answered questions from reporters on the background, principles and main contents of the formulation of the Guide.

Q: What is the background and significance of the Guidelines?

A: The 14th Five-Year Plan is the first five-year plan to embark on a new journey to comprehensively build a modern socialist country and promote the building of a beautiful China. To further strengthen ecological protection and restoration of rivers and lakes, The Technical Outline for the preparation of the 14th Five-Year Plan for Water Ecological Environment Protection in Key River Basins and the Guide to the Storage of the Central Ecological Environment Fund Project Reserve (2020) issued by the Ministry of Finance and the Ministry of Agriculture both regard constructed wetlands as an important measure to improve the ecological environment of rivers and lakes. The "Guiding Opinions on Promoting the Utilization of Sewage Resources" jointly issued by ten ministries and commissions also regards constructed wetlands as an important way to realize the utilization of sewage resources.

In recent years, Shandong, Anhui, Yunnan, Shanghai, Qinghai and other places have taken the lead in building constructed wetlands in key nodes such as the downstream of sewage treatment plant outfalls, river inlets into lakes, and branches into main streams according to local conditions, using ecological methods to further improve the drainage and micro-polluted river water after treatment standards, and achieving good environmental, ecological and social benefits. At present, the above places have raised the relevant practice to local standards.

At the national level, the former Ministry of Environmental Protection and the Ministry of Housing and Urban-Rural Development respectively issued industry standards such as the "Technical Specifications for Constructed Wetland Sewage Treatment Engineering" and "Technical Regulations for Natural Sewage Treatment Engineering" in 2010 and 2017, but the above standards regard constructed wetlands as high-concentration sewage treatment facilities. It has not adapted to the new requirements of improving the water quality of wastewater treatment plants to meet the standard of drainage and micro-pollution, achieving the water environment target of rivers and lakes, or the reuse of reclaimed water under the current new situation; In addition, the above standards focus on design, and the operation and maintenance of constructed wetlands are not considered enough.

Therefore, it is necessary to summarize local beneficial experience in a timely manner, formulate and introduce relevant technical documents, and better guide the relevant work of water purification of constructed wetlands in the country.

Q: What is the main purpose of the Guide?

A: The main consideration of the "Guide" is from the perspective of "effective, easy to use and solve problems", through the systematic guidance of the whole process of the water purification project of constructed wetlands from design, construction, acceptance to operation and maintenance, to prevent and dispose of common problems of constructed wetlands, stabilize the water purification effect of constructed wetlands, and achieve long-term effective operation.

Q: Everyone is interested in the compilation of the Guide. Could you briefly introduce the main contents of the Guide?

A: The Guide consists of four chapters: The first chapter is the general provisions, which clarifies the purpose, scope of application and basic principles of the Guide, and defines the main terms. The second chapter to the fourth chapter is the main part, which is the design, construction, acceptance, operation and maintenance of the constructed wetland water purification. The chapter "Water purification design of constructed wetland" mainly makes detailed provisions on the overall design, process design, auxiliary engineering, etc., including the standard specifications to be implemented, the applicable process types and design parameters. In the chapter "Construction and Acceptance", the requirements and standards for the construction process of the main project, auxiliary project and supporting facilities are systematically specified, and the management and technical requirements for the completion of environmental protection acceptance are clearly defined. The "Operation and maintenance" chapter puts forward the ability and qualification requirements for the operation and maintenance units and operation management personnel of constructed wetlands, and stipulates the conditions and standards that should be met in production debugging, daily operation and maintenance, safety production, emergency management, monitoring and recording, etc. In addition, a list of suggested measures is put forward for the classification of common problems of constructed wetlands.

Q: What are the basic principles that should be followed in the process of implementing water purification in constructed wetlands?

A: First, accurate positioning. The water purification project of constructed wetland only undertakes the task of improving the water quality of low-pollution water such as the effluent of sewage treatment plant discharged to the standard, and does not act as a pollution control facility for direct treatment of production and domestic sewage.

Second, ecological priority. The water quality purification project of constructed wetland should give priority to the use of natural or near-natural ecological ways to improve the ecological quality of water through the synergistic effects of physics, chemistry and biology in the wetland ecosystem, and it is not appropriate to use strengthening measures such as adding chemicals to purify water quality. Native species should be chosen to avoid invasion by alien species.

Third, adapt to local conditions. The site, layout, process, parameters and vegetation of the water purification project of constructed wetland are selected according to the actual situation of local temperature, rainfall, landform, land resources, etc. Encourage the use of pits, depressions, wasteland and other easily used land, urban green belt, corner land and so on to carry out the construction of constructed wetlands.

Fourth, the performance is clear. As a pollution control facility, the water quality purification project of constructed wetlands should strengthen the supervision of water entering and leaving and clarify the requirements for pollutant reduction. Adhere to both construction and management, improve the operation and maintenance mechanism, guarantee the operation and maintenance funds, and achieve long-term operation.

Q: In 2010, the former Ministry of Environmental Protection issued the "Technical Specifications for Constructed Wetland sewage Treatment

Engineering", may I ask what are the differences and highlights of the "Guidelines" released this time?

A: First, the scope of application is different, and the requirements for entering and leaving water are further clarified. The "Guide" stipulates that the treatment object of the constructed wetland water purification project is the effluent from the sewage treatment plant, the micro-polluted river water, the farmland backwater and similar low-pollution water. When the treatment object is the effluent from a centralized sewage treatment plant, the effluent should meet the local water pollutant discharge standards. When the treatment object is river lake water, farmland backwater, the inlet water should be better than the local water pollutant discharge standards. It is clear that the effluent water quality should in principle meet the requirements of the ecological environmental protection objectives of the receiving water body, and when there is a demand for recycled water reuse, the effluent water quality should meet the requirements of the relevant water quality standards for recycled water reuse.

The second is to increase the list of climate zoning, process comparison and common problem measures to achieve accurate guidance for zoning classification. According to the climate conditions of each province and city, the country is divided into five climate zones, namely, cold regions, cold regions in summer and winter, hot regions in summer and warm regions in winter, and moderate regions. According to the current situation of ecological protection and restoration of constructed wetland, the paper puts forward the suggestions of site selection and appropriate process type. In view of the problems that the reconstruction light pipe affects the water purification effect and service life of the wetland, detailed guidance is made for the operation and maintenance of the wetland from the aspects of production debugging, daily operation and maintenance, and effluent monitoring, etc., and the causes and countermeasures are given for 18 common problems in 5 categories such as wetland silting and effluent quality decline, so as to facilitate the use of operators.

The third is to further deepen the design, construction, acceptance and operation and maintenance of the whole process guidance. From the perspective of practicality and operability, the operational requirements, key parameters and technical standards of each link are fully refined and realized. Not only to meet the "easy to use" of technical personnel, but also to meet the "good management" of managers. In addition, in the face of the long-term problem of "heavy construction, light management" of wetlands, we are highlighting the requirements of operation and maintenance in the "Guide", and stipulate how to effectively guarantee the long-term operation and conservation of constructed wetlands from the technical level.