Nitrogen Removal Test Of Combination Ecological Process And EFDC Numerical Simulation

With the development of urbanization,river water is facing severe water pollution problems,affecting people’s production and life.Traditional chemical treatment methods need to put in large quantities of chemicals,which are easy to produce new pollution and increase the cost of treatment.Therefore,choosing ecological methods to solve water pollution problems has become a focus of attention.The results of 16 water quality monitoring sections of Xinkai River show that the water bodies of Xinkai River,Yongchun River,Leijiagou and Xixin Reservoir,Taipingchi Reservoir and Baluo Lake are all inferior type V water bodies.In order to ensure the water quality safety of the diversion project of"Yin-Xin-Ji-Tai",Changchun city combines the ways,nature and characteristics of water area and water pollution,proposes to use the"four methods in series"integrated ecological water control technology（aeration oxidation pond method,channel surface flow wetland method,ecological river method,reed wetland purification method）to purify the water body of Xin-Kai River,restore the river ecosystem and self-purification function.Taking each treatment unit as the research object,this paper introduces the design process,analyses the effect of constructed wetland filler on ammonia nitrogen adsorption,determines the optimal adsorption conditions,and carries out hydrodynamic simulation to simulate the flow situation of each treatment unit in the study area.The main results are as follows:1.Combining with the actual water quality of the project,in order to meet the effect of pollutant removal,according to BOD₅ load,the treatment areas of Acoman oxidation pond,surface flow constructed wetland and ecological river were determined as 1134 m²,1800 m² and 3540 m²,respectively.2.The treatment effects of each treatment unit on COD,ammonia nitrogen,Tri-nitrogen and total phosphorus are as follows:combined process>multi-stage constructed wetland>Acoran pan-oxidation pond.The highest treatment rates of COD,ammonia nitrogen,trinitrogen and total phosphorus were 53.3%,91%,97.07%and76%,all occurring in summer.The removal efficiency of pollutants by the combined process meets the design effluent standard.Suitable temperature and dissolved oxygen content have a positive impact on the treatment effect of ammonia nitrogen and COD.The removal rate of pollutants is high when the temperature is increased and aeration equipment is added.3.Design expert was used to design the experiment of NH₄⁺adsorption on bioceramics.Single-factor and multi-factor experiments based on reaction time,particle size and initial NH₄⁺concentration were carried out.The order of influence of the three factors from significant to unimportance was determined as initial concentration>particle size of bioceramics>reaction time.At the same time,the response surface model established by the experiment has a high fitting degree.The particle size is 9.61 mm,the initial concentration is 120 mg/L,and the adsorption amount of NH₄⁺is the largest when the reaction time is 1434 minutes.4.The hydrodynamic models of Akoram oxidation pond,surface flow constructed wetland,ecological river and mixed plant constructed wetland were constructed.The water depth was fitted by EFDC software.The model results show that,except for the difference between the simulated and actual monitoring values,the simulated water levels of the other units are close to the actual monitoring values.The measured and simulated water levels can be controlled within the range of 0 to 0.03m,and the relative error can be controlled between 0 and 15%.But the whole can better reflect the changing trend of water depth in the study area.