Analysis For The Effect Mechanism Of Phosphorus On Nitrogen Migration And Transformation In Deep Soil Infiltration System

Environmental problems, such as massive emission of sewage, eutrophication and phosphorus deficiency in soil, lead us to walk on the development road of recycle treatment- irrigating their farmlands with sewage. This sewage treatment technology, which could make sewage useful, resource recycling and environmental friendly, is a pratical use of soil infiltration system, the topic in this paper. In soil system, denitrification as the limiting step of nitrogen removal, usually occurs in deep soil because of the anaerobic conditions, while, the shallow soil a large of adsorption of phosphorus due to its strong intercept action. So the question whether it is the lack of phosphorus, the nutrition element affects the activity of denitrifying in soil, that inhabits denitrification, thus cause low nitrogen removal rate remains to be proven. Based on the above two points, this topic regard soil infiltration system as the main subject, combined with the assumption that phosphorus is the possible limiting factor of denitrification in deep soil, discuss the effect of phosphorus on nitrogen migration and transformation in deep soil infiltration treatment.The organic glass PVC column with a radiu of 0.3m and a height of 2.0m was used to simulate the real soil infiltration system, with 2.0m deep soil loading in the glass, the soil came from Beijing shunyi, irrigation with simulated sewage of different phosphorus concentration, to research the transitions and transforms of TOC, N, P in soil infiltration system, as well as the influence of phosphorus on them, especially the influence on nitrogen migration.Soil has a strong adsorption and fixation of phosphorus, which is the main way of removing phosphorus; increasing phosphorus loading can help extending the vertical migration distance, at the same time promoting the transformation effect of phosphorus in the surface soil, speeding up the phosphorus adsorption saturation of the surface soil. Nitrogen removal in soil is mainly depend on the process of nitrification – denitrification; high phosphorus loading can improve the removal rate, especially the denitrification rate; a certain soil depth is needed to complete the nitrogen and phosphorus purification. Among the three situations in the experiment,when phosphorus loading is 30mg/L, the denitrification is more quick, the soil depth needed to reach the effluent standard,0.8m, is also the smallest among them.