Optimization Of Heating Method Of Horizontal Subsurface Flow Constructed Wetland In Solar Greenhouse

Artificial wetland sewage treatment technology,has the characteristics of simple construction,low initial investment,high pollutant removal efficiency,but in winter due to low temperature artificial wetland will be frozen,and plant wilting microbial activity reduced resulting in artificial wetland can not work normally or treatment effect is poor.In order to solve the problem of low treatment efficiency of constructed wetland in winter,a horizontal subsurface flow constructed wetland system was designed by combining constructed wetland and solar greenhouse.Through sampling and testing,the characteristics of water quality and water temperature of rural domestic sewage were analyzed,and the optimal operating temperature of horizontal subsurface flow constructed wetland in winter was studied experimentally.The mathematical model of thermal environment of horizontal subsurface flow constructed wetland in solar greenhouse is analyzed theoretically.The variation of water temperature in the heating pool in solar greenhouse was studied experimentally and numerically.The hourly heating load of the constructed wetland to maintain the optimal operating temperature in winter was calculated by numerical simulation,and the life-cycle cost optimization design of the heating system of three different heat sources was carried out to provide technical support for improving the pollutant removal efficiency of the constructed wetland in winter.The main work and conclusions of this thesis are as follows:1)The water quality and water temperature characteristics of rural domestic sewage in typical villages and towns in Xuzhou area were sampled and tested,and the main water pollution index values were determined.Domestic sewage was allocated in the laboratory with chemical reagents,and the pollutant removal rate of horizontal subsurface flow constructed wetland under different sewage temperatures was experimentally studied.The optimal operating temperature of horizontal subsurface flow constructed wetland in winter was determined to be 18℃.2)The mathematical model of thermal environment of horizontal subsurface flow constructed wetland in solar greenhouse was established.According to the actual situation,the heat transfer process of solar greenhouse,heating pool and constructed wetland is simplified,and the heat balance equation of the horizontal subsurface flow constructed wetland with heating type in solar greenhouse and the calculation formula of solar radiation intensity received in solar greenhouse are established.3)Taking 48 h as a warming period,the field measurement of the horizontal subsurface flow constructed wetland of the solar greenhouse warming type was carried out for 14 days.The variation law of air temperature and soil temperature in solar greenhouse,the variation law of sewage temperature in heating pool,the thermal insulation effect and pollutant removal efficiency of constructed wetland were obtained by field measurement.The results show that the sewage in the heating pool has a certain heating effect,the thermal insulation performance of the horizontal subsurface flow constructed wetland is good,and the water quality of the wetland outlet reaches the standard.4)COMSOL MULTIPHYSICS(?) multi-physics simulation software was applied to obtain the law of sewage temperature change in the heating pool of the solar greenhouse warming type horizontal subsurface flow constructed wetland by numerical simulation.The results showed that the numerical simulation results were in good agreement with the field measured results,and the correlation coefficient between the simulated value and the measured value was above 0.96.The maximum absolute error is 1.64℃,the maximum relative error is 8.7%,and the relative error is within the allowable range of the project.5)COMSOL MULTIPHYSICS(?) multi-physics simulation software was used to numerically calculate the air temperature,soil temperature and effluent temperature of the horizontal subsurface flow constructed wetland system under the optimal operating temperature of the solar greenhouse warming type in winter in a typical meteorological year in Xuzhou,and calculate the hourly heating load of the constructed wetland system.Through the cost analysis of the whole life cycle,the hot water heating system of electric heating,air source heat pump and biogas boiler was optimized.The average cost per ton of water treatment in the life cycle of the three different heating methods was 1.321,1.253 and 1.272,respectively,and the hollow air source heat pump of the three heating methods was relatively better.This thesis has 51 figures,22 tables and 94 references.