Study On Isolation And Identification Of Phenol-degrading Strain Of Heterotrophic Nitrification-aerobic Denitrification And Its Characteristics

Phenolic compounds are the common organic pollutants in industrial wasterwater,such as petroleum chemical industry,coking plants.It is one of priority control pollutants in our country.Although at low concentration,they do harm to biomass for its toxic properties.High concentration phenolic wasterwater can not only be a serious threat to human being,but also make the ecological environment more deteriorative.Microbical methods of phenolics removal are preferable in wastewater treatment process as relatively low costs and small possibility of a secondary pollution.The key of this method is to isolate microorganism that have the capacity of phenol degradation.Considering the common serious occurrence of nitrogen pollution in many phenolic wastewaters,besides,heterotrophic nitrification and aerobic denitrification,a newly biological nitrate removal technology,can simultaneously degradation of carbon and removal of nitrogen in wasterwater.Carbon resource is not dosed during denitrification process.This provides the theory basis for simultaneously phenol degradation and nitrogen removal.It is also show that microorganisms which have the capacity of simultaneously phenol degradation and nitrogen removal do exist in all possibility.In addition,the heterotrophic nitrification-aerobic denitrification mechanism of removal nitrogen and high concentration of phenolic wastewater treatment must be further studied.It is helpful to apply the isolated strain to the practical engineering.And it has advantageous of grasping the metabolic process of the strain exactly.With high initial phenol as carbon source,a newly stable and metabolically versatile simultaneous heterotrophic nitrification and aerobic denitrification strain was isolated from the domesticated microbes under aerobic condition using the traditional microbial technology.The optimum degradation condition were investigated(temperature 30?,initial pH 7.2 and shaking speed of 180 r/min).Its capacity of phenol degradation reached 1400 mg/L under this best condition.Based on its physiology,biochemical characters and the analysis of its 16S rDNA gene sequence,the isolate named PD-7 was identified as a member of the genus Diaphorobacter.With phenol as the sole carbon and energy source,the process of its growth was investigated using Haldane kinetic model at the phenol concentration range of 0-1400mg/L.Specific substrate degradation rate and the specific cell growth rate are related using Luedeking-Piret equation.The fitted curve had a good correlation with test measured.The parameters were:?max(maximum specific growth rate)=0.324 h-1,Ks(half-satruration constant)=9.36 mg/L,Ki(inhibition constant)=146.72 mg/L.Based on the enzyme analysis of phenol degradation process,the strain could be induced to synthesize intracellular catechol-2,3-dioxygenase.The preliminary inference was that the strain Diaphorobacter sp.PD-7 degraded phenol through between an open mid-loop way.Nitrogen removal under aerobic condition showed almost entirely removal of 120.69 mg/L ammonium nitrogen within 75h in the heterotrophic nitrification medium with initial 1,400 mg/L phenol.During the whole cultivation,there were 5%NO2--N and 13%NO3--N accumulated.Nitrate nitrogen removal reached 91.5%within 60 h in the denitrification medium with initial 1,400 mg/L phenol and 165 mg/L nitrate nitrogen.Moreover,by adopting the method of cell disruption,the cells were broken,and its enzyme activitise measured through the substrate changes.Hydroxylamine oxidase,periplasmic nitrate reductase and nitrite reductase were certain expressed in the isolate during the whole nitrogen removal process of strain Diaphorobacter sp.PD-7.