| The study and application of wastewater treatment with constructed wetland started in the end of 1970s. The 4th international conference on constructed wetland in Vienna, Austria symbolized that as a kind of special new wastewater treatment technology, constructed wetlands started to enter the fields of water pollution and water control. By now, it was widely applied to treat municipal wastewater, industrial wastewater, mineral wastewater, oil exploit wastewater, non-point resource pollution and eutrophication treatment. Many of countries in west Europe and North America have constructed plenty of wetlands. However, applied engineering examples are lack of in China, only in Shenzhen, Guangdong province, Jiaonan, Shandong province, Shenyang, Liaoning province 3 constructed wetland wastewater treatment plant were built. As a complete ecosystem, constructed wetland is made of water, medium (soil, silver sand, coarse sand, gravel etc.), vegetation (reed, cattail) and microbe realize effective wastewater purification utilizing multi-ecosystem's cooperation process of physical, chemical and biological through filtration, adsorption, deposition, ion exchange, vegetation assimilation and microorganism decomposition. It belongs to a kind of ecological technology of wastewater treatment. Constructed wetlands can be divided into 3 types, surface flow constructed wetland, subsurface flow constructed wetland, vertical flow constructed wetland. Among these 3 types, former 2 types both have engineering application, while vertical flow constructed wetland has no been reported on its application, still in pilot-scale study stage.The practical situation of wastewater treatment plant had been built in our country demonstrated that the pollutant removal efficiency of constructed wetland was high. The efficiency of surface flow constructed wetland is: COD (80%), BOD5 (86%), SS (91%), TN (64%), TP (75%). The concentration of effluent from constructed wetland can meet the second level standard. As for the purification effect, constructed wetland can be alternative to conventional biological treatment technology, but it is equivalent to 1/6～1/3 in invest, 1/7～1/4 in operation and maintenance of conventional biological treatment. However, constructed wetland needs large lands, about 4～6 times of conventional secondary biochemical treatment plant.Surface flow constructed wetland in the Changchun Carriage Factory occupied area 0.52hm2. Its organic load is 67kg BOD/ hm2.d and hydrological retention time (HRT) is 0.58d. Determination data demonstrated that treatment efficiency of main pollutants in this system is: SS (65%), BOD5 (33%), COD (29%), NH3-N (12%). In 20℃, the decomposition coefficient of BOD is 0.80d-1 and of COD is 0.67 d-1. The practice showed that even in cold winter, the system still is operational, but its efficiency drops down a little. The surface flow constructed wetland in the Changchun Carriage Factory derived from an aerobics pond, so it is not a typical example of industrial wastewater treatment through surface flow constructed wetland.Constructed wetland wastewater treatment technology is suitable to our country, especially in expansive village, small-middle scale city, adopting it to treat wastewater and non-point source pollution. In arid, semi-arid and salt-alkalization area, it is feasible to constructed wetland to treat industrial and municipal wastewater. This technology is adoptable in those cities where have useable land or pond, when the first or secondary effluent cannot meet water environmental require and need to be polished for landscape use. Non-point source pollution from runoff and effluent of farmland also should mainly adopt surface constructed wetland. Subsurface flow constructed wetland is feasible for small volume and disperse wastewater, at the same time it need strict management. General small town, village and cold climate area are not suitable to construct subsurface flow constructed wetland. Sole Surface constructed wetland shouldn't be adopted to treat indus...
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