Study On Mutation Breeding And Biological Characteristics Of Denitrifying Phosphorus-accumulating Bacterium

Nitrogen and phosphorus pollutants are the main factors leading to eutrophication of many inland lakes,reservoirs and even rivers.Their synergistic removal is the main goal of biological wastewater treatment.Conventional sewage treatment process can effectively reduce the biodegradability of organic matter and suspended solids in the water,but the nitrogen and phosphorus nutrient removal can only exist at the same time from 10% to 20%,a large number of phosphorus containing wastewater directly discharged into the water.Due to the biological removal of nitrogen and phosphorus are two relatively independent processes,in the same processing system will inevitably produce some contradictions,contradictions such as age,carbon source competition,nitrate interference etc..The discovery of denitrifying phosphorus accumulating bacteria?DPAB?provides the possibility to solve the contradiction between carbon source utilization and SRT,so that the two processes of biological nitrogen removal and phosphorus removal can be carried out simultaneously.In this paper,the denitrifying phosphorus accumulating bacteria were prepared by Protoplast Mutagenesis technique from the enrichment,screening and isolation of denitrifying phosphorus accumulating bacteria from high performance,carbon and nitrogen sources,temperature,p H value etc,studied its suitable growth conditions and effect of removal of nitrogen and phosphorus.And the establishment of bacteria proliferation dynamics and degradation dynamics equation of nitrogen and phosphorus.The main results of this paper are as follows:?1?Three highly strains of DPAB were screened and named N11,N14 and N23,which were screened by nitrate reduction and denitrification and phosphorus uptake experiment.and then the three strains were identified as Thauerap sp.,Klebsiella sp.and Arthrobacter sp.by physiological and biochemical experiments,16 S r DNA gene sequence analysis and phylogenetic tree construction.?2?The optimum conditions of protoplast preparation were determined for denitrifying phosphorus accumulating bacterium of N11,N14 and N23.The protoplasts of DPA N11,N14,N23 were mutagenized by UV,UV + lithium chloride?Li Cl?,ultraviolet + ethidium bromide?EB?and ultraviolet + diethyl sulfate?DES?,seven mutants were selected,and their ability to synchronize nitrogen and phosphorus removal is stronger than the starting strain?P<0.05 or P< 0.01?.Four mutant strains?UDN11-02,UEN11-01,UEN14-02,UEN23-03?,which denitrification rates or phosphorus removal rates were higher than wild fungus more than 10% were subcultured,after five generations their denitrification rates and phosphorus removal rates were relatively stable.?3?Nitrogen source,carbon source,temperature and p H had significant effects on the growth of strains?P<0.05 or P<0.01?.Three strains of wild bacterium and 4 strains of mutants bacterium suitable for the growth of nitrogen source is LB medium;the suitable carbon source were: LB medium,propionic acid,sodium acetate,sodium acetate,sodium acetate,LB medium,LB medium,respectively;the suitable temperature were 35 ?,30 ?,35 ?,35 ?,35 ?,30 ?,35 ?,respectively;suitable for p H were 8,8,7,8,7,8,8,respectively.The concentrations of COD,NO3--N and PO43--P in the culture supernatant and PHA in bacterium's body of the 7 strains were significantly changed in the anaerobic-anoxic culture conditions.After incubation for 48 h,nitrogen removal rates were 81.2 %,84.7 %,80.9 %,91.5 %,91.4 %,93.6 % and 86.1 % respectively,the removal rates of phosphorus were 81.0 %,73.8 %,59.3 %,82.0 %,82.3 %,87.0 % and 78.0 %,respectively.The phosphorus metabolism patterns of N11 and N23 were different from those of traditional denitrifying phosphorus-accumulating bacterium,and the other five strains had the same phosphorus metabolism pattern as traditional denitrifying phosphorus-accumulating bacterium..?4?Nitrogen and phosphorus degradation models and population multiplication models of denitrifying phosphorus accumulating bacteria under anoxic condition were established,and the parameters of the corresponding model were determined.The model of nitrogen and phosphorus degradation is: ???,model parameter values are: v_max?P?=0.6538 mg/L/h,Ks?P?=0.1212 mg/L,k?P?=35.96 mg/L;v_max?N?=0.6474 mg/L/h,Ks?N?=1.7288 mg/L,k?N?=118.15 mg/L.Different culture time of population under Logistic proliferation model:???,model parameter values are: K=544.01mg/L,d=3.9749,v=0.29671 /h,The population growth model under different inoculum size was:???,the model parameter values are: k=0.358/h,K=0.769,mg/L,S=3.547,mg/L.