Thermal Environment Analysis And Winter Operation Of Constructed Wetland In Cold Area

Constructed wetland is advanced wastewater treatment technology that has emerged in recent years.It is man-made ecosystems that treat wastewater through the combined action of the physical,chemical,and biological processes between plants and microorganisms in the wetland.It has a simple structure,low energy consumption,water quality is good,easy to operate,low operating costs,etc.,it is a very promising sewage treatment technology.However,the effect of constructed wetlands on wastewater treatment is affected by such factors as the types of wetlands,the load of pollution,the growth of wetland plants,operation modes and temperature changes.Among them,the influence of temperature change on the wastewater treatment effect of wetland system can not be ignored.Therefore,at present,the constructed wetlands are mostly used in the south area and have not been widely popularized and used in the northern part of our country.The cold winter temperature condition in the north is the main reason why constructed wetland technology has not been widely used in northern China.In this paper,we read the existing literature to adjust the operating conditions of constructed wetlands to find the optimum operating conditions of constructed wetlands in winter,and through adding appropriate insulation materials to the constructed wetlands for heat preservation,so that the constructed wetlands,a good prospect of sewage treatment technology can be promoted and used in northern China.In this paper,the constructed wetland in the cold area is taken as the research object to establish the biochemical reaction model and the heat transfer model of the constructed wetland respectively.Firstly,the biochemical reaction model of constructed wetland was established by using SubWet2.0 software.Secondly,the heat transfer model of constructed wetland was established by using Gambit software.The model was divided into grids and boundary conditions.SubWet2.0 software and Fluent The software simulates the biochemical reaction in the wetland bed and the heat transfer of the bed respectively.By changing the inlet water temperature,the hydraulic retention time and the water distribution method,the removal rate of the constructed wetland pollutants and the distribution of the temperature field in the constructed wetland are obtained The effects of different operating conditions on the temperature distribution and pollutant removal in constructed wetlands were compared and analyzed.Through the heat preservation of the constructed wetland,the removal rate of wetland pollutants and the distribution of the temperature field are simulated to determine the optimal operating conditions of the constructed wetland in winter.Through the study of this paper,it is found that with the increase of inlet water temperature and hydraulic retention time,the bed temperature and the removal rate of pollutants in wetland gradually increase.When the hydraulic retention time reaches 2d,the bed temperature and the removal rate of each pollutant tend to be stable.In addition,by changing the water distribution of wetlands,making wetlands more uniform water distribution,but also can improve the bed temperature and pollutant removal rate.On the basis of this study,we found that with the increase of the thickness of the insulation layer,the temperature of the bed body and the removal rate of pollutants are gradually increased by adding the civil cloth as the insulation material of the wetland.When the thickness of the insulation layer increases,Slowdown.Finally,the simulation results are compared and analyzed,and the optimal insulation thickness corresponding to different influent temperature and different hydraulic retention time are summed up to obtain the optimal operation condition of constructed wetland in winter.In this paper,the effects of different factors on the artificial wetland bed temperature field and wetland pollutant removal rate in cold area are simulated to provide technical support and theoretical basis for the promotion and use of constructed wetland in the cold areas of northern China.