Study On The Pollutant Removal Law And Mechanism Of Artificial Wetland And Its Dynamic Model

The research progress of Constructed Wetland for surface water pollutants at home and abroad,this paper takes the constructed wetlands of the sewage treatment system in second-groove Fenghuang River in Chengdu as the case example,from the analysis of water quality monitoring and assessment of river health risk assessment and treatment level evaluation,laboratory simulation and dynamic analysis have been carried out artificial wetland contaminant removal regularity,mechanism and dynamics analysis.The water quality is firstly sampled and monitored for assessing the current situation of water quality by adopting the recommended formulas in environmental impact assessment;then determine the pollution extent quantitatively through healthy risk assessment for toxic substance in Fenghuang River,different risk evaluation models are established based on the detected concentrations of Genotype toxic substances,cancerogenic substance and Non carcinogens;and then quantify the treatment effect of constructed wetlands in sewage treatment project of second-groove Fenghuang River,the removal efficiency as well as the regulations of COD,TN,TP and SS by treatment of wetlands are researched,a quantitative assessment of the sewage treatment level of the constructed wetland was carried out to assist in the simulation of the constructed wetland system in the laboratory.Finally,the removal kinetics model was established to predict the discharge concentration of the outlet of the constructed wetland system under the condition of a certain hydraulic retention time and a certain influent concentration.The research results are as follows:1.Artificial rapid infiltration system pretreatment upstream sewage treatment system using the Phoenix river two ditch,an artificial wetland system for processing,the original serious exceed the standard upstream runoff downstream can reach when the main indexes can meet the“surface water environmental quality standard"(GB3838-2002)limit class standard,at the same time,the "urban sewage treatment plant pollutant discharge standard(GB18918-2002)" a standard can be achieved.2.By carrying out the two phoenix river water environmental health risk assessment,it can be confirmed the carcinogen cadmium(Cd)and chromium(Cr)in river water environment for years the level of risk generated by personal controllable.Specifically,on the one hand,this kind of carcinogenic substances and the International Commission on Radiological Protection(ICRP)recommended maximum acceptable content and the U.S.Environmental Protection Agency advocated in drinking water can hurt a person's all kinds of heavy metal pollutants in the risk limit comparison,it did not reach the limit;on the other hand for the exposed population,such carcinogenic substances will not bring obvious threat to its health risk.At the same time,the model and the demonstration results show that the two gully of Phoenix river has a good effect on the establishment of safety surface water source protection system and river water risk management.3.The water pollutant concentration monitoring of the artificial wetland system,on the one hand,total phosphorus removal rate reached 53%,the removal rate of SS reached 74%,the removal rate of COD reached 35%,the total nitrogen removal rate of more than 52%,it showed that the artificial wetland system has good processing level;on the other hand,the artificial wetland treatment process the microbial derived DOM is relatively high,the high degree of humification.FRI method(fluorescence zone integration)showed that DOM was more biodegradable than humic substances and fulvic acids,which contained tyrosine like substances(PI,n).The study also showed that COD,TN,DOC and many kinds of tyrosine substances(PI,n)were positively correlated with the degree of humification,which will lead to COD,TN,DOC and DOM decreased with the increasing of the decomposition and humification degree.4.The constructed wetlands simulated system is constructed in laboratory,through the modeling of treatment for the domestic sewage,the regulations of migration,transformation and degradation of pollutants such as COD,TN and TP are further researched,the degradation mechanism of pollutants,especially the nitrogen and phosphorus,is also studied.The reasons of TN and TP with low removal rate in artificial wetland system are analyzed,which lay a foundation for optimizing the pool structure of artificial wetland,composition of filtering media in rapid infiltration filter and operational mode,improvement for the removal efficiency of pollutants.5.Based on the theory of organic matter degradation in artificial wetland,the expressions of organic matter concentrations are established,which belongs to the deterministic model.And then by exploring the stochastic theory,the Wiener process is induced into the deterministic model,the organic matter concentration stochastic model is established;At the same time,in order to study the migration and transformation of nitrogen elements and simulate the ecological process of nitrogen elements in the constructed wetland system,STELLA software was introduced to establish the corresponding ecological dynamics model.The results show that,in a given period of time,the changes of nitrogen and growth of plants and microorganisms in the constructed wetland system can be predicted by the ecological dynamics model,and good results are obtained.