A Reaction Kinetics Study Of Decarbonization And Nitrogen Removal In Shallow Surface Flow Constructed Wetland

Along with the water pollution and the water shortage gradually deteriorated, domestic sewage treatment is facing new problems. Constructed wetland is a wastewater treatment technology developed in the late1970s, which has a strong pollutant removal ability, water quality and stability with easy operation and maintenance management, low cost of engineering construction and operating, and strong adaptability to load change, and can be used as an effective alternative to a conventional sewage treatment technology. At present, subsurface flow constructed wetlands and deep surface flow constructed wetlands are mainly the constructed wetland systems for researching and application, shallow surface flow constructed wetlands less in China. The experiment investigated the major effect factors of the shallow surface flow constructed wetland system to purify sewage, such as hydraulic loading, water surface height, the initial concentration of pollutants. To provide technical support and reference for broad applications of shallow-flow constructed wetland system, the studies that focus on purification effect, influencing factors and removal mechanism of the technology for sewage water are carried out in this thesis.The experiment’s results reveal that the chief major factor of influencing COD removal is the hydraulic loading, followed by the water surface height in the system with strong anti-COD ability. The optimal conditions for the removal of COD is obtained as0.15m3/m2。 d hydraulic loading, the water height of20cm, COD influent concentration of270mg L.Ammonia and total nitrogen of the system are removed in the optimal hydraulic loading0.2m3/m2·d.Removal rate of ammonia nitrogen on the surface of the water is best. And the total nitrogen removal with the surface height increases in volatility trends, and reaches max on the surface of water’s height15cm.Based on dissolved oxygen changing within the system, some conclusions can be drawn from the present study:Dissolved oxygen increase with the raise of the water surface height within the system, and the highest dissolved oxygen content is discovered on the surface where oxygen conditions are best. With the increase in dissolved oxygen within the system, the COD removal rate gradually changes higher, and the ammonia nitrogen removal rate gradually changes higher but the increase rate slows, and total nitrogen removal is now increasing and then decreasing.This experiment takes the lead in exploring the correlation about the sewage purification effect of the shallow surface flow constructed wetland system with the hydraulic loading, the surface height, the initial concentration of pollutants, and puts forward the primary reaction kinetics equations according to the system assumptions of the experiment, but the conclusion limited for this simplified system. On the premise of more laboratory equipments, more experiment conditions those affect the effect of domestic sewage purification system can be further discussed, such as changing matrix compositions, wetland plant, wetland system in the variation in content of oxygen, providing the basis for the solution to the actual working conditions.