Identification Of Rhizosphere Microorganisms Isolated From Several Kinds Of Wetland Plants And Research On Their Sewage Purification Effects

The wetland is a comprehensive ecosystem that has many kinds of ecologicalfunction, such as flood control and water storage, climate regulating and waterpurification. As a new kind of wastewater treatment technologies, the constructedwetland composing of substrates, aquatic plants and microorganisms, could purifywaste water by filtration, absorption, coprecipitation, ion exchange of plant anddegradation of symbiotic microorganism, which referring to physical, chemical andbiological mechanisms. Microorganisms, be it a major decomposer, probably play akey role in degrading pollutants and purifying wastewater in the constructed wetland.The purpose of this research is to identify the composed species (mainly for bacteria)of rhizosphere microorganisms isolated from several wetland plants, and then selectsome strains with effective ability that can remove COD and nitrogen contained in thewaste water, this can provide theory and application reference in the constructedwetland construction.Thus this paper focused on introducing isolation and identification of somerhizosphere bacteria from several wetland plants, as well as the purification effect oneffluent quality of the isolated bacteria. The16S rDNA sequence analysis techniquewas used for bacterial identification, and then both physiological and biochemicalcharacteristics of the selected strains were measured, such as salt tolerance, oilhydrolysis and proteolytic and so on. COD and ammonia nitrogen are adopted as twoendpoints for sewage determination, both changes would be tested after vaccinationwithin48h (every12h determination once) then removal rate in each group after48hwould also be calculated to determine the purification efficiency. Potassiumdichromate method and hash water quality analyzer（DR2700） were used fordetermination of COD and ammonia nitrogen concentration used. Results are asfollows:1)12purified strains in total were isolated, including four strains Bacillus, two strains of Janthinobacterium, one strain of Rhodanobacter, Planomicrobium,Aeromonas, Planococcus and Pseudoxanthomonas, as well as one strain of which thetaxonomic status has not yet been identified by its homologous sequences.2) With the highest salinity tolerance, strain M3could be cultivated in theenvironment with10%salinity, while its optimum salinity for growth was1%. ZL2and ZL11could grow in the substrates with a salinity of less than10%, and theoptimum salinity for growth is1%. BL1could be cultivated below7%salinity, whichcould be in better status with the salinity of0and1%. Other strains excluded abovecould be only cultivated in the substrates with a salinity of0and1%. All strainsexcept for BL18and BL21had grease hydrolysis characteristics, of which M3had thehighest ability. Hydrolysis circles appeared around the colonies of BL15, BL18, ZL2,M3and S9, indicating that these bacteria possessing ability of hydrolyzing proteinscompared with others strains.3) The concentration of COD and ammonia nitrogen within48hours of thesewage into which different strains were introduced, showed different changes. After48hours, strains with COD removal efficiency (with a larger removal rate than thatthe control group) including ZL2(98.04%), M1(89.01%), BL1(87.86%), M3(76.57%), ZL11(64.99%), S9(61.87%), BL15(48.30%), S5(45.58%), BL21(42.76%), BL8(28.77%). ZL2had the highest COD removal efficiency, of which theremoval rate was significantly higher than that of other treatment groups (P <0.05). Inaddition, M1, BL1, M3, ZL11and S9also had a good removal efficiency, all ofwhich the COD removal efficiency were above60%.After48hours, strains with ammonia nitrogen removal efficiency (with a largerremoval rate than that the control group) including BL1(99.53%), ZL2(92.31%), theM1(91.49%), E. coli BL21(41.98%), ZL11(35.32%), S9(25.52%), S5(22.30%),M3（18.39%）,BL15（17.01%）. BL1had the highest ammonia nitrogenremoval efficiency, of which the removal rate was significantly higher than that ofother treatment groups (P <0.05). Followed by ZL2and M1, the ammonia removal ofboth were more than90%but without significant differences from others(P>0.05).The ammonia removal efficiency of other groups were much weaker.In conclusion,there are twelve purified bacterial strains we have got,and eleven of them have been identified.Except for the strain M3which is pathogenic bacteria，we finally got five strains with high effect on COD removement(ZL2,BL1,M3,ZL11and S9) and two strains with high effect on NH3-N removement(BL1and ZL2).