Optimization Study Of Domestic Sewage Treatment In Rural Areas By Using The Integrated SBR And Wetland Processing Approach

The rural economy is weak,the geographical environment is complex,and the characteristics of domestic sewage discharge are significantly different in time and space.Designing a decentralized sewage treatment process with economic,environmental and social benefits according to local conditions is of great significance to promoting rural domestic sewage treatment.Comprehensively using research methods such as field investigation,physical test and numerical simulation,according to the actual situation of rural areas in Xuzhou,the domestic sewage treatment process of"Sequencing Batch Reactor（SBR）+Downflow Vertical Underflow Constructed Wetland"was carried out.optimization studies.The effects of temperature,operation mode,plant type of constructed wetland,packing method and hydraulic load on the operation effect of the combined process of the SBR process system were studied,and the optimal design and operation scheme of the combined process in different seasons was determined.An engineering case of rural domestic sewage treatment.The main research contents and conclusions of this paper are as follows.1)The field investigation has mastered the current situation of rural domestic sewage treatment in Xuzhou and the characteristics and laws of its discharge.The domestic sewage in the rural areas of Tongshan District is still scattered;the domestic water consumption in summer is significantly higher than that in winter,and the water quality is better than that in winter;there is a significant correlation between water temperature and atmospheric temperature（P<0.05）,and the daily variation range of water temperature is small.2)The combined process physical experiment platform of"SBR+Downflow Vertical Subsurface Constructed Wetland"was independently constructed,and the isothermal adsorption characteristics of phosphorus and NH₃-N by constructed wetland fillers,and the effects of SBR system temperature,operation mode and constructed wetland plant species on the operation of the combined process were obtained.The isotherm adsorption characteristics of the volcanic rock and gravel for phosphorus and NH3-N are in line with the Langmuir and Freundlich isotherm adsorption models（R²>0.9）.The removal rate was positively correlated with temperature（P<0.05）;Properly prolonging the aeration and stirring time of SBR process is beneficial to reduce the effluent concentration;The former has better removal effect on COD and NH₃-N than the latter,and the removal effect on TP is inferior to the latter.3)A numerical simulation model of constructed wetland was established,and the influence of packing composition and hydraulic load on the purification effect of constructed wetland was obtained.The numerical simulation and physical experiment results showed good consistency and no significant difference（P>0.05）.The multiple regression equations of COD,NH₃-N and TP removal rates in vertical subsurface constructed wetland effluent with different filler heights of filter material layer were established（P<0.05）.Reducing hydraulic load can improve the removal rates of COD,NH₃-N and TP in constructed wetland effluent.4)The optimal design and operation scheme of the combined process is determined.The SBR process adopts operation mode 1 in cold season（water intake,stirring for 4 hours,continuous aeration for 3 hours after the start of stirring for 1 hour,sedimentation for 1 hour,drainage and standing for a total of 1 hour）,system temperature of 20°C.In warm season,operation mode 4（water inlet,standing for 1h,continuous aeration for 2h,sedimentation for 1h,drainage,standing for a total of 1h）withput the control of temperature is prefered;the artificial wetland is planted with cattails,and the optimal filler composition of the filter layer is 5～8 mm volcanic rock:8～16 mm gravel:8～16 mm volcanic rock=375 mm:625 mm:0,the hydraulic load of the incoming water should not be greater than 0.35 m³?m^-2?d^-1.Reducing the hydraulic load can improve the removal rate of COD,NH₃-N and TP in the effluent of constructed wetland.5)The combined process engineering case of"SBR+constructed wetland"with daily treatment water volume of 20 t in Xuzhou area was designed.Solar energy storage and heat exchange device is selected as heating unit.Through seasonal adjustment of system temperature and operation mode,7300 T of domestic sewage can be treated after one year of operation,and the emission reduction of COD,NH₃-N and TP is 2.77 t,0.55 t and 0.07 t,respectively.The social and environmental benefits are significant.There are 64 figures,50 tables,and 107 references in this thesis.