Investigation Of Chemical Sewage Treatment Using Danhe Artificial Wetland

With the rapid development of economy in recent years, there is a great change along Dan River Basin. Due to the surrounded by chemical industries, the water of Dan River Basin has been polluted very seriously and its treatment has practical significance.In Jincheng city, planning the project of artificial wetland will be constructed in order to achieve the blue sky and clear water. The project includes two period projects, the first period project has been completed and the second one is constructing. The paper focuses on the first period project of Danhe wetland. The first period of the project has been all built in the A region, and the wetland has been divided into A1, A2, A3and A4four wetland beds. Cattail has been planted in Al and A3area and reeds has been planted in A2and A4area.The sewage derived from chemical industries has been treated in Dan River upstream by artificial wetland and the effect of sewage treatment at different area has been compared in constructed wetland in view of pH, DO, COD, BOD, ammonia nitrogen, total nitrogen and total phosphorus, and even removal rates of fluoride and cyanide. Some conclusions are as follows:(1) The pH values in the different area of artificial wetland system changes smoothly, it basically maintains at between7.4-7.6. The DO values in different exports of artificial wetland system changes sharply, the main reason is that the DO value is not only related to the temperature, but also related with the ability of radial oxygen of aquatic plants. The wetland system water has the relatively strong self-regulating capacity due to large bodies of water.(2) The changes of each water index of different exits in artificial wetland system are almost consistent; these indexs include COD, BOD, ammonia nitrogen, total nitrogen and total phosphorus. The concentration of index in each export changes with the concentration of water inlet. These results indicated that the wetland system can be able to achieve better removal efficiency for chemical sewage.(3) The fluoride and cyanide which are hard to degrade in wetland system are not basically removed, and the concentration of exports and imports are almost the same. This indicates that the wetland system cannot remove the basic undegraded compounds. It should be consider a combination of wetland and other technology if these pollutants are polluted very seriously.(4) The removal efficiencies of COD, BOD, ammonia nitrogen, total nitrogen and total phosphorus are obvious, and the COD removal efficiency of 30.37-61.43%and the BOD removal efficiency of30.64-70.29%, ammonia nitrogen removal efficiency of7.29-59.68%and total nitrogen removal efficiency of9.05-63.95%as well as the phosphorus removal efficiency of-7.55-24.05%. The phosphorus removal rates appeared negative value; the reason is the phosphorus from plants into water.(5) The total nitrogen and total phosphorus has been determined for different parts of plant, such as roots, stems and leaves after the plants harvest in artificial wetland. The nitrogen absorption capacity by reeds is better than cattails, but the phosphorus absorption capacity by reeds is almost approaching to that by cattails. Not only reeds but also cattails the nitrogen and phosphorus absorption capacity of aerial parts is better than underground parts, so harvesting plants is a useful method for removal nitrogen and phosphorus of sewage.(6) Removal rates of total nitrogen in sewage by cattails and reeds absorption which occupies the proportion of the TN removal rate in cattails wetland system and reeds wetland system are1.68%and3.05%, but removal rates of total phosphorus in sewage by cattails and reeds absorption which occupies the proportion of the TP removal rate in cattails wetland system and reeds wetland system are39.1%and39.0%. The plants absorption on phosphorus is better than the absorption on nitrogen, but the contribution of plants absorption is small relative to the overall removal efficiency and the plants absorption is not the dominant position on removal of nitrogen and phosphorus in wetland system.In summary, in this paper, the removal efficiency of chemical sewage in the first period of Dan River artificial wetland has been investigated. But there are many inadequacies due to time constraints and the limitations of practical engineering, so it is essential to improve the engineering from the design and provide a foundation basis for the effect of wetland sewage treatment.