Study On Simultaneous Nitrification And Denitrification Bacteria Resisting Extreme Environment With The Assistance Of Osmotic Compensation Solute

Ammonia is considered as the main pollutant of water.Ammonia pollution has become a serious social and environmental problem.SND denitrification is a simultaneous denitrification process with heterotrophic nitrification and aerobic denitrification under the same operating conditions and in the same reactor.SND denitrification technology has become a hotspot in the research of biological denitrification.Because it has many advantages,such as high efficiency of nitrogen removal,the system in a stable pH,suitable for the treatment of ammonia wastewater containing organic pollutants,the process operation is simple,etc.Although SND denitrification has many significant advantages,ammonia wastewater treatment will be restricted to a large extent in some extreme environments.The reason is that the reverse environment can inhibit the normal growth and metabolism of certain SND denitrification strains,leading to reduced or even loss of nitrogen removal ability.Many industrial and agricultural wastewater often have the characteristics of high ammonia and NaCl concentration.Most SND denitrification strains will be restricted due to lack of resistance and the denitrification efficiency will be reduced.Ectoine(1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid)is an osmotic compensated solute which is synthesized by moderate halophiles in response to high osmotic stress.Ectoine can maintain intracellular and extracellular osmotic pressure balance,it is often used as a protective agent for cells,enzymes and nucleic acids.SND strain can obtain resistance after absorbing Ectoine,so as to improve the denitrification efficiency of ammonia wastewater in reverse environment.Based on the characteristics of Ectoine to assist the cells in resisting the extreme environment,investigating the effect of its assistance to the denitrification properties of the SND strain will have an important significance for the purification of high concentration ammonia wastewater in the extreme environment.An SND denitrification strain P07 was isolated and purified from the aeration tank of a sewage treatment plant in Dalian.The strain P07 was identified as Pseudomonas by the results of 16S rDNA and morphological identification,named as Pseudomonas sp.P07.The growth characteristics of strain P07 were investigated.The optimum carbon source for growth was sodium glutamate,optimum carbon source concentration(calculated as C)was 15 g/L,initial pH was 7,strain P07 is not a salt-tolerant bacterium.The Influencing factors of denitrification of strain P07 were investigated.The optimum denitrification carbon source was trisodium citrate,oxygen supply and NaCl concentration were 30 mL/300 mL conical flask and 0,C/N and initial pH were 5 and 8.The SND process was detected in the optimum condition,after 120 hours of treatment,NH4+-N concentration decreased from 2000 mg/L to 146.30 mg/L,and the denitrification rate reached 91.86%.The assistance to resist the reverse environment by different osmotic compensation solutes were investigated.When Ectoine was added as the promoter,the denitrification rate reached the highest,which was 47.3%,and relatively low concentration(50 mg/L)of Ectoine can play a significant role in resisting the reverse environment for denitrification.In addition,the effects of Ectoine on strain P07 denitrification in different concentrations of NH4+-N and pH were investigated.When the concentration of NH4-N was 1000?2500 mg/L,the effect of Ectoine on the SND denitrification was the best,and the denitrification rate increased evenly by nearly 20%;Ectoine has a strong effect on SND denitrification of strain P07 when the pH condition was 6-8,especially when the pH was 6,the denitrification rate was increased by 29.4%compared with the control which did not add Ectoine.Therefore,it can be used for the treatment of ammonia wastewater in which NH4+-N concentration was between 1000?2500 mg/L and pH was within the range of 6-8 in practical applications.The combination of Pseudomonas sp.P07 and Ectoine secreting strain Halomonas sp.B01 was applied to denitrification treatment of simulation wastewater with high concentration of salt and ammonia.The nitrogen concentration decreased from 475.2 mg/L to 140.8 mg/L after 120 hours of treatment,the denitrification rate was 70.2%,and there is no accumulation of nitrates and nitrites in the process.