The Experiment On The Treatment Of Water Body Containing Phosphorus By Multistage Combination Of Constructed Wetland And Pond

With China’s economic development, people become more and more aware of the environmental dependence of human beings as well as concerned about the pollution of water body. The eutrophication of water body has been discussed in recent years. In China, it is of practical significance to control the eutrophication of lake by phosphorus removal because the concentration of phosphorus is the limiting factor of lake eutrophication. Because of the low concentration of phosphorus in water and the larger treatment, the traditional methods are difficult to deal with. Combination system of constructed wetland and pond has a good effect on low concentration phosphorus as well as strong adaptability to the load change, which is the lack of traditional methods. Multistage combination system which increase units on the basis of combination system of constructed wetland and pond, can adapt to more complex water environment.The effects of water temperature, phosphorus pollution concentration and hydraulic retention time(HRT) on the treatment of phosphorus and organic pollutants in rich nutrition water body by multistage combination system have been discussed in this paper, and the removal mechanism of phosphorus and organic pollutants in the system analyzed. The effects of water temperature, phosphorus pollution concentration and hydraulic retention time(HRT) on the treatment of phosphorus pollutants have been firstly researched in the system by using orthogonal test method and SPSS software which could be used to confirm influence degree of these three factors on the system as well as establish the optimum operating parameters of the system for phosphorus removal. Secondly, single factor analysis method is used to study the concentration changes of phosphorus and organic pollutants when the multistage combination system operating in different water temperature, hydraulic residence time and concentration of phosphorus pollution. Finally, under the optimal operating condition, variation of phosphorus pollution concentration along the system has been studied to ensure the most efficient unit for phosphorus removal in the multistage system and analyze removal mechanism of phosphorus.This study have mainly get following conclusions.1) orthogonal test:Total phosphorus(TP) removal rate of the multistage combination system could be 85 ~ 98.90%, and TP concentration of effluent could reach class Ⅲ of Environment Quality Standards for Surface Water(GB3838-2002). Influence degree for TP removal in the multistage combination system influence could be concluded asfollows: water temperature, phosphorus pollution concentration, hydraulic retention time. All of the 3 factors could have significant influence on TP removal. The optimum operating parameters of the system for phosphorus removal is concluded as follows: phosphorus pollution concentration is 1.35 mg/L, the water temperature30 ℃, hydraulic retention time 6d.2) hydraulic retention time test:In addition to the hydraulic retention time of 2d, TP concentration of effluent could reach class Ⅴ of the Standards. System of TP removal rate increases with the increase of hydraulic retention time. With the increase of HRT, system of removing the DTP and DOP were higher in turn. Multistage system TP first order kinetics model of combination system correlation coefficient is 0.9143, the model can well reflect the TP removal process of the system.3) the influence of seasonal variation on the system test:Seasonal variation of multistage combination system has obvious correlation, TP removal effect temperature of correlation and TP removal rate was 0.83. Different seasons of the system on phosphorus treatment effect is as follows: summer, autumn,spring, winter. Influenced by seasonal change on DIP, DIP treatment effect comparison of the four seasons is as follows: summer, autumn, spring, winter.4) the mechanism of the test:TP removal of multistage combination system mainly occurs in the pond 1.Multi-stage pond combination artificial wetland system, the removal efficiency of organic matter is as follows: surface flow constructed wetland 1, pond 1,subsurface constructed wetland, pond 2, surface flow constructed wetland 2. DIP removal in the system mainly occurs in the pond 1 and 2, DOP removal occurs mainly in the pond 1and subsurface constructed wetland, and PP removal mainly in surface flow constructed wetland 1 and subsurface constructed wetland.