Isolation And Identification Of Oligotrophic Aerobic Denitrifying Bacteria And Denitrification Characteristics

As a kind of major pollutants in water, nitrogen is one of the main causes ofeutrophication. There are physical-chemical methods and biological methods toremove nitrogen pollution, biological denitrification become a hot topic with itscost-effective, no secondary pollution, etc. In this paper, we discussed the screeningmethods of aerobic denitrifying bacteria in depth, and the screening was efficientaerobic denitrifying bacteria scanning electron microscopy and16S rRNA moleculesidentified. We also investigated the impact of environmental factors on the effect ofnitrogen removal, and putting the combined dominant bacteria into raw water to makea small test analysis. The main conclusion of the study include:(1) We collected sediments in the reservoir, Shandong Zaozhuang. The aerobicdenitrifier in sediments is domesticated by gradually reducing the content of sodiumacetate and sodium nitrate. Then we obtained the plant colony of the same colonycharacteristics after separation and purification. There are totally412stains. In pureculture conditions, the412aerobic denitrifier were nitrogen removal analysisrespectively. After6days of culture, there are21stains’ removal rate of the sum ofnitrate nitrogen and nitrite nitrogen more than60%. Selected three of the bacterias withhigh removal rate (nitrate and nitrite nitrogen and the removal of more than70%,total nitrogen removal rate over40%) ZN1, ZN2and ZN3bacteria as a source offurther research.(2) Gram strain results showed: three dominant bacteria ZN1, ZN2and ZN3were negative (G-); it’s showed that three bacterias are all bacillus belonging further byresult of electron microscope, which ZN1have depression, ZN2was like peanuts, ZN2and ZN3are relatively full. It’s showed that ZN1and ZN3belongs to the iron-reducingbacteria, ZN2belonging to the Zoogloea sp. by comparing gene sequence obtainedusing molecular biological methods to measure this three bacteria ation of16S rRNAsequencing with the GENBANK database. Comparison this three dominant bacteria16S rRNA sequences and reported aerobic denitrifying bacteria phylogenetic analysisshowed that this three dominant bacteria and reported with good homology. Byperiplasmic nitrate reductase subunit gene (napA) amplification experiments provedthis three bacteria periplasmic nitrate reductase does exist, it is driven catalytic aerobicdenitrification.(3) At the pure culture conditions, in selective aerobic denitrifier medium, at30℃,120r/min cultured47h, strain ZN1, ZN2and ZN3nitrate nitrogen removal ratereached more than80%, total nitrogen removal rate reached more than40%. Researchon the effects of environmental factors derived strains ZN2nitrogen removal, the bestnitrogen ratio was12/1, the optimum initial pH value was7, the best inoculation was1.0%, the optimum temperature was30℃. Also it is showed that, ZN2strain has goodnitrification properties, it can also be nitrite as nitrogen aerobic denitrification.(4) Take a raw water in one reservoir, ZN1, ZN2and ZN3strains was adopt to theraw water respectively. We made three dominant bacteria gradually adopt to the rawwater environment by gradually changing the proportion of medium and raw water.Then putting the adaptation strain to raw water to make a small test in different amount.The results showed that after running the40d, when the dosage was100ppm, totalnitrogen and nitrate nitrogen removal are the highest, and total nitrogen removal rateup to about45%, nitrate nitrogen removal rate was about65%. The result provides ascientific basis for poor nutrition aerobic denitrifying bacteria in the water ofmicro-polluted water body restoration application.