Screening And Compounding Of Low-temperature-resistant Dominant Bacteria And Their Application In Constructed Wetlands In Cold Regions

Constructed wetland treatment system has become the main technology for advanced treatment of tail water of municipal wastewater treatment plant and purification of river and lake water.In view of the problem that microbial activity in constructed wetland decreases under low temperature conditions in winter,resulting in the decrease of pollutant removal efficiency,this paper takes the vertical subsurface flow constructed wetland wastewater treatment system in cold area as the research object,and at low temperature of 4-7 ?,from the angle of microorganisms.Starting from the degree of low temperature,the treatment efficiency and internal microbial distribution of subsurface constructed wetland were explored;the dominant strains resistant to low temperature were screened out and constructed as a composite microbial agent with high degradation efficiency;the microbial population distribution changes before and after adding microbial agent were compared by adding microbial agent to simulated constructed wetland system to enhance the treatment effect under low temperature conditions.The results are as follows:The start-up time of subsurface constructed wetland under low temperature is about 10 days longer than that under normal temperature.After stable operation,the treatment efficiency of COD,ammonia nitrogen and total nitrogen are 80%,48%,38%,respectively.The treatment efficiency of low temperature constructed wetland is only 74%,17%and 27%.The bacterial content of each layer in the simulation device of subsurface constructed wetland under low temperature is relatively constant.There are less than one to two orders of magnitude under temperature conditions.Carbon removal bacteria,ammoniating bacteria,nitrifying bacteria,nitrifying bacteria and denitrifying bacteria were screened out,and two strains with better efficiency were screened.The optimum proportion of denitrifying bacteria was ammoniating bacteria:nitrifying bacteria:denitrifying bacteria=2:3:1:2,and the removal rates of ammonia nitrogen and total nitrogen were 16.59%and 17.86%respectively.The optimum proportion of the agent is carbon removal bacteria:denitrifying bacteria agent=4:1,the removal rates of COD,ammonia nitrogen and total nitrogen are 28.81%,21.34%and 18.59%,respectively.The removal rates of COD,ammonia nitrogen and total nitrogen can be increased by 4.06%,5.78%and 7.69%respectively when the dosage of bacteria is 0.5%of the unit volume in the low temperature subsurface flow constructed wetland simulator.But after 10 days,the removal rate of each index decreased,and should be repeated in 10 days.The optimum dosage was 1%of the unit volume,the total nitrogen could reach the first A standard,and the COD removal rate could reach more than 80%.The number of ammoniating bacteria,nitrifying bacteria,denitrifying bacteria in the enhanced group increased in different degrees after adding compound microbial agent.