Technical guide for water purification 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.