What is a constructed wetland?

As for constructed wetlands, it can be said that they have a long history in China. Since people began to plow with knives and cook with fire, China has its own artificial wetland. Those rice fields, artificial fish ponds and so on. They are the most qualified old people in constructed wetlands, and they will tell people stories about wetlands. Month after month, year after year, they worked tirelessly for the great cause of environmental protection. Until one day, people gave them a formal name-artificial wetland! Constructed wetland technology originated in 1950s. After decades of development, it has become a mature sewage treatment technology and has been widely used in developed countries in Europe and America. In recent years, this technology has also been widely used in China, and has produced good environmental governance effects.

What is the magic of constructed wetlands, which can play a great role in water purification and water restoration? Constructed wetland is a kind of ground built and supervised by human beings, similar to swamp. In the field of environment, the research and application of constructed wetland sewage treatment are more and more extensive. In the process of sewage flowing in a certain direction, the three synergistic effects of physics, chemistry and biology in wetland natural ecosystem are mainly used to realize efficient purification of sewage through filtration, adsorption, precipitation, ion exchange, plant absorption and microbial decomposition. Please see the following: The report "Constructed Wetland: Beautiful Scenery by Fuxian Lake".

1. Constructed Wetland: Controlling Pollution by Natural Methods "A large flock of seagulls flew to Fuxian Lake!" People in Yaonigou area on the north bank of Fuxian Lake are arguing over the red-billed gull from Siberia. What attracted hundreds of seagulls to fly to the north shore of Fuxian Lake? People in the environmental protection circle hit the nail on the head: Fuxian Lake is sky-blue and water-blue, and the constructed wetland makes seagulls find a new home.

In June 2002, the first large-scale constructed wetland in Yunnan Province was built in Yaonigou, the north bank of Fuxian Lake, under the careful design of Nanjing Institute of Geography and Lakes and Yuxi Institute of Environmental Science of Chinese Academy of Sciences. After the foul sewage flows through the constructed wetland, it becomes a clear trickle. From June 5 to 10, 2003, the second constructed wetland was built and put into use on the north bank of Mario River. The monitoring results of environmental protection department show that the effluent quality of Yaonigou constructed wetland reaches Class III standard of surface water, and that of Maliaohe constructed wetland reaches Class II standard of surface water. When I came to the Mario Estuary in the suburb of Chengxian County, the reporter saw the magical constructed wetland. At the entrance of the wetland, workers salvage the garbage and floating objects in the water. After the black sewage passes through the slag retaining door,

Slowly flow into the wetland. This artificial wetland, which covers an area of nearly 30 mu, is built in the shape of several "fields" and separated by cement ridges. There are many kinds of aquatic plants 10 in different areas. After the sewage enters the constructed wetland, the first pond it flows into is the biological oxidation sedimentation tank, where the sewage is oxidized. After phosphorus, nitrogen and other nutrients in sewage are filtered layer by layer and fully absorbed by these plants, the nutrients contained in it have been greatly reduced. Then it flows into a pool paved with sand and stones, where plants grow, and the sewage is precipitated and filtered again when it is undercurrent underground; The last process is completed in the surface shallow-flow biological purification pool, and the algae and aquatic plants in the pool reabsorb the nutrients in the water. At this time, the sewage has become crystal clear. At the outlet not far from the lake, the originally turbid and smelly sewage has turned into a clear spring and flowed into the beautiful Fuxian Lake. The ability of constructed wetland to treat sewage is amazing. Yaonigou is one of the seriously polluted rivers entering the lake on the north bank of Fuxian Lake. After the completion of the Yaonigou constructed wetland covering an area of 26 mu, the daily sewage treatment capacity will reach 1 10,000 tons. The monitoring shows that the removal rates of total nitrogen and total phosphorus are 50% and 40% respectively, the removal rate of suspended solids is over 80%, the removal rates of chemical oxygen demand and biochemical oxygen demand are 60% and 50% respectively, and the water quality is improved 1 ~ 2. According to reports, the pollution control effect of Maliaohe constructed wetland is better than that of Yaonigou constructed wetland, and the effluent quality reaches Class II standard of surface water.

2. Ecological benefits: hold the throat of non-point source pollution.

Agricultural non-point source pollution is the biggest killer of Fuxian Lake, and domestic sewage and farmland runoff are the main reasons for the decline of water quality. According to statistics, in 2002, the amount of chemical fertilizer applied in the runoff area of Fuxian Lake was 4968 1 ton, of which about 20% of nitrogen fertilizer and 15% of phosphorus fertilizer were lost with water. The application amount of pesticides is nearly 30 tons, and the loss is about 30%, which directly leads to the increase of total phosphorus and total nitrogen. The monitoring results of environmental protection department show that the runoff area of Fuxian Lake enters the lake every year with 2487 tons of nitrogen fertilizer and 0/000 tons of phosphorus fertilizer, which poses a serious threat to the ecological environment of the lake area. However, crop waste and domestic garbage flow into the lake with the river water, which also causes pollution. At present, the amount of garbage flowing into the lake reaches 33,600 tons every year. In the runoff area of Fuxian Lake, the annual discharge of domestic sewage is 4.06 million tons, and the discharge of human and animal feces is 600,000 tons. A considerable part of these pollutants enter Fuxian Lake through surface runoff and stratum leakage. Mario River is one of the rivers with serious pollution in the suburbs of Chengjiang County. There are large areas of farmland on both sides of the river. Fertilizer, pesticide and crop waste flow into Fuxian Lake along with the river, and some domestic sewage and garbage from the county also enter the lake. Especially in the rainy season, the Mario estuary is in chaos. Under the ravages of sewage and garbage, the nearby lakes are eutrophic, and the good place for swimming in the past has become a dirty pool. Now, the Maliaohe constructed wetland is put into use, workers salvage garbage at the entrance of the constructed wetland, and all the sewage flows into the wetland, and the sewage flows into the lake after "washing". In the next few years, a large-scale constructed wetland will be built next to Fuxian Lake. 9 km sewage intercepting ditch, 100 hectare constructed wetland and 700 hectares landscape wetland will be built on the north bank of Fuxian Lake. Xu Shaowu, director of the Environmental Protection Bureau of Chengjiang County, said that by 20 10, only Chengjiang will build 28 pollution control projects at the end of the river entering the lake, the main content of which is to build artificial wetlands. After the large-scale construction of the constructed wetland in Fuxian Lake, the constructed wetland will control the main rivers that inject pollution into Fuxian Lake and hold the throat of non-point source pollution.

3. Economic benefit: the sewage treatment cost is low.

In the interview, Ma Defen, deputy director of Chengjiang County Environmental Protection Bureau, calculated such an account: Chengjiang County Sewage Treatment Plant processes 4,000 tons of sewage every day, while it costs 0.98 yuan to treat 1 ton of sewage, and nearly 4,000 yuan is invested every day; However, the daily sewage treatment capacity of Maliaohe constructed wetland is 1.45 million tons, and it only needs 0.03 ~ 0.05 yuan to treat 1 ton sewage, and the daily investment is only a few hundred yuan. In other words, the sewage treatment cost of constructed wetland is only 1/20 of that of sewage treatment plant.

4. Social benefits: After sightseeing, I was inspired. In Maliaohe constructed wetland, dozens of acres of constructed wetland are like a picture of environmental protection, and the constructed wetland will turn "sewage into clean water", which is amazing. Walking on the ridge between wetlands is like walking in lakeside park. The well-known and unknown plants in the wetland are absorbing dirt and accepting dirt, but they are also showing vigorous vitality, and the surrounding water gurgles. If you are interested, you can get on the boat, pick and manage these lovely creatures with the workers, and feel a "national black tour".

For a time, the constructed wetland has become a beautiful scenery beside Fuxian Lake while controlling pollution. In recent years, many wetlands that benefit mankind from nature have become tourist hotspots. In Tengchong, Yunnan, beihai wetland, a national nature reserve, has become a highlight of tourism, attracting more and more tourists. In some places, constructed wetlands have also become tourist attractions and environmental education bases.

It can be seen that the constructed wetland has been built, which is a beautiful scenery. It can not only treat sewage with little money, but also build a scenic spot. The same is probably true of the green environment that we have been advocating.