Separation And Screening Of Cold-tolerant Nitrogen-retaining Microorganisms

With the development of industry and agriculture,excessive inorganic nitrogen is discharged into the water body,causing a series of environmental problems.In the cold area,content of dominant bacteria in the water is less easy to lose with the water body because of low water temperature in winter in the sewage treatment plant,resulting in a decrease in the biological treatment effect of sewage.In view of the current situation of poor microbial treatment of low-temperature domestic sewage,six cold-resistant nitrogen-degrading bacteria with heterotrophic nitrification and aerobic denitrification were isolated and screened from the excess sludge at the bottom of the aquarium of the water station on campus.The bacteria grow well at 8 ?.After morphological observation,bacterial staining and physiological and biochemical experiments,referring to the "Common Bacterial System Identification Manual" and "Berger's Bacterial Identification Manual" for preliminary identification of strains,Bacillus,deputy Cocci,Alcaligenes,Paracoccus,Pseudomonas,Pseudomonas were identified respectively.The growth curves of each strain were tested at different temperatures,and the specific growth rate and generation time of different strains were calculated.It was found that B3,B5 and B6 were more suitable for growth at 8?than 20?,and all strains were active at 4?.By changing the pH,temperature,carbon-nitrogen ratio and dosage of the strains,the effects of environmental factors on the nitrogen removal performance of the strain were studied.It was found that the pH,temperature and carbon-nitrogen ratio had a great influence on the nitrogen removal performance of the strain.The strains dosage had little effect on its denitrification performance,and the effect of temperature and carbon to nitrogen ratio on the heterotrophic nitrification performance of the strain was greater than that on its aerobic denitrification performance.Strain B6 showed the strongest tolerance to environmental factors based on effects of comprehensive environmental factors on the heterotrophic nitrification and aerobic denitrification of strains.Microbial immobilization experiment of strain B6 was conducted by adsorption-embedding-crosslinking method using powdered activated carbon as adsorbent,sodium alginate and polyvinyl alcohol as embedding agent,and anhydrous calcium chloride-saturated boric acid solution as cross-linking agent.Through orthogonal test and comprehensive balance method,with ammonia nitrogen andnitrate nitrogen removal rate as reference indicators,the optimal conditions for immobilization were determined to be 1% sodium alginate content,12% polyvinyl alcohol content and 3% activated carbon content,and the crosslinking time at 12 h.By changing pH and temperature,it was found that the immobilized material could still achieve higher ammonia nitrogen and nitrate nitrogen removal effects in a short time,and improve the nitrogen removal performance of the single strain at 15?.