Study On Selection And Training Of The Strain Degrading High-chlorinated Biphenyls And Its Degradation Characteristics

PCBs, a class of very complex synthetic polymer chemicals, was started in 1929 worldwide large-scale industrial production, and then was banned on opening globally in 1970s. In the course of consumption such as leakage or intentional, unintentional discharges, PCBs has caused large-scale pollution, and posed a serious threat to human security, and thus, are in need of treatment urgently.PCBs at home and abroad for the treatment of pollution can be generally divided into sealing method, thermal treatment, chemical, microbiological and other methods at present. Sealing method was not possible to fundamentally solve the problem of PCBs contamination, and because of the leakage phenomenon due to shell corrosion, environmental hidden trouble still exist. Thermal treatment is a widely used method on waste disposal, but mostly at an experimental stage domestically. Chemical method can complete waste disposal, needs simple equipment and easy to design into a vehicle devices. There are more microbiological stydies currently. However, the current domestic biodegradation study has not made major progress, only for some preliminary work, also degrading bacteria and the selection has not yet acquired significant progress with the problems such as the small number of selected strains, low-efficiency. As a more economical method which can transform PCBs and other persistent organic pollutants in a way of protecting environment, there are broad prospects for development. Therefore it is necessary to do in-depth research.In this dissertation, the efficient predominant strains of PCBs was screened from the PCBs contaminated soil. Through the methods of one time investment of high concentration compound and added relatively low concentration compound timingly and quantitatively, tow strains of P1 and P2 are acquired. Using 7 item physiological and bio-chemical experiments, catalase, glucose oxidase fermentation, the oxidation of ethanol fermentation, in V-P, methyl red experiments, hydrolysis of starch, gelatin liquefaction, hydrogen sulfide generation, to strains of P1 and P2. Through 16S rRNA gene sequence homology analysis, P1 strain can be identified as Alcaligenes, while P2 belonging to Bacillus.Seeing about degradation with different nitrogen source, bacteria can both use organic and inorganic nitrogen source, but different in usage levels. Overall inorganic nitrogen medium significantly lower than organic nitrogen. With the majority of microbial nitrogen demand of the law. Between pH 5-8, mycelium of PCBs have some degradation. Cell growth was restrained with the acid or alkali, dechlorination speed reduced; With the temperature rising, cell growth conditions gradually improved, when the temperature reached 30℃, on the 7th day, P has degraded PCBs up to 97.86%. High temperature helps the microbe attack the PCBs with special position of Cl by 2,3-dioxygenase and Extracellular Polymeric Substances adsorption of organic; Inoculation of 5mL has a best degradation effect. When the inoculum size is small, the rate of degradation increases with the amount of bacteria gradually increasing, but when their excessive coverage of bacteria in poor nutritional status, growth and metabolism to a certain extent; Loading volume on the effects of bacterial degradation of PCBs affect more apparently. When liquid volume is very low, high content of dissolved oxygen promote the growth of bacteria, handle the corresponding concentration of PCBs with strong capacity, but excessive liquid cause the bateria gain not enough oxygen, thus, growth is restricted.Control experiment showed that reduce of decconcentration of PCBs due to the adoption of bacteria. Then, PCBs was degraded because of the decrease of pH.Kinetic experiments on bacteria are conducted, and do a comparison through experimental data double countdown chart. Analysis of both the control method of mapping parameters: it can be seen that the experimental method and the results of the penultimate double mapping obtained are similar, which further verified that mixed bacteria P biological degradation of PCBs in the reaction process is a dynamic process irreversible.Using artificial water distribution as raw water, PCBs as the sole source of carbon and nitrogen, adding different concentrations of PCBs according to the experimental demands, after a period of tame, degradation experiments show that the cell has certain wastewater degradation.This dissertation aim at the high-chlorinated biphenyls, selected predominant strains with high efficient degradation, through identification and its degradation studies, providing basic data for in-depth study of microbial degradation of PCBs contaminants.