The Application Of Constructed Wetland Model No.1to Water Body Remediation And Domestic Wastewater Treatment By Constructed Wetlands

In this paper, the Constructed Wetland Model No(CWM1) was employed to describe thebiochemical reaction for pollutants in constructed wetlands. On this basis, the filtration and adsorption of mediums on particles in subsurface flow constructed wetlands, the sedimentationof particles in surface flow constructed wetlands and the assimilation of plants were considered for the impacts on reaction rates of each component. As a result, a model for pollutants removal with constructed wetlands was built up, which was then adopted to a small scale water improvement project for Weihe River in Xi’an Section, a surface flow constructed wetland of sewage treatment station in Tongyuan Town, Gaoling County as well as a subsurface flow constructed wetland for sewage treatment project of Shuilu Bay Resort in Lantian. The simulated analyses of pollutants at these points were conducted and the adaptability of the model was verified.The following conclusions were drawn:(1) The influent concentrations of chemical oxygen demand (COD),5-day biologicaloxygen demand (BOD5) and ammonia nitrogen (NH4+-N) of the in-site experiments were71~280mg/L,28~161mg/L and15~36mg/L respectively. The effluent COD, BOD5andNH4+-N concentrations of the three-stage sub-surface flow constructed wetland were16～47mg/L,2~4mg/L and2~8mg/L respectively. Removal efficiencies of COD, BOD5andNH4+-N of the sub-surface flow constructed wetland were77.1%~93.5%,92.7%~98.7%and66.7%~90%respectively.(2) The effluent COD, BOD5and NH4+-N concentrations of the two-stage surface flowconstructed wetland were36～75mg/L,5~12mg/L and6~15mg/L respectively. Removalefficiencies of COD, BOD5and NH4+-N of the surface flow constructed wetland were39.7%~85%,78.6%~94.9%and44.4%~66.7%respectively.(3) Plants tested in the water quality improvement projects were reed, Miscanthusfloridulus （Labill.）Warb. and cattail. According to the in-site experiments, reed and cattailgrew well in constructed wetlands, and Miscanthus floridulus （Labill.）Warb. can not to be awetland plant in this environment. Constructed Wetlands was covered by native plants whenmanagement was stopped. (4) CWM1mainly described the dynamic process of microbial growth. In this paper,taken the filtration and adsorption effects of the constructed wetland on substrates and plantsassimilation into consideration, the contamination removal model was constructed andapplied to the simulation of the contamination removals by the two-stage surface flowconstructed wetland and the three-stage flow constructed wetland.(5) The improved CWM1was utilized to simulate the dynamic process of the twoconstructed wetlands located in Tongyuan town, Gaoling County and Shuiluwan resort,Lantian County respectively, and the simulation results were in accordance with those ofexperimental results basically. The simulation results of the model to the wastewater treatmentplant located in Shuiluwan resort, Lantian County was better than those of Tongyuan town,Gaoling County.The following innovation results were obtained through experiments and theoreticalanalysis:(1) The pollutants in the Weihe River along urban reaches of Xi’an were regarded as theobject of the study. According to the method suggested by the CWM1, the parameters ofwater quality in the Zaohe River were defined.(2) On the basis of CWM1, taken the filtration and adsorption effects of the constructedwetland on substrates and plants assimilation into consideration, the contamination removalmodel for the constructed wetland was constructed.(3) The improved CWM1was calibrated and utilized to simulate the operation of waterquality improvement projects and domestic wastewater treatment projects， and thesimulation results were in good accordance with those of experimental results.