Screening And Characterization Of Phenol-Degrading Bacteria From Coking Wastewater

China is the main country of the coking production, coking consumption and coking export. However, the outdated production techniques and equipments seriously polluted the water environment. In 2010, something has been done toactively promote the optimization and upgrading of coking industry in China. It is planned and ruled that the development mode would change from the mainly expanding capacity to the higher-valued coking products in the way of "low carbon" and "green" direction. The coking wastewater treatment are paid more attentions.Coking wastewater mainly contains phenol, polycyclic aromatic hydrocarbons, heterocyclic compounds, tar and other organic compounds except for cyanide, sulphide, high concentrations of NH3-N and other inorganic compounds. Due to the complicated compositions, heavy chromaticity and strong toxicity, the coking wastewater is a typical organic wastewater difficult to treat. Since July 1,2010, the implementation of coking industry emission standards (GB 16171-2011) provides the limits of direct discharge of COD, for the existing factory is from 150 mg/L to 100 mg/L, the new enterprise from 100 mg/L to 50 mg/L. Clearly, phenolic substances as the main contribution of COD, their degradation efficiency has the direct relation with meeting the requirements of the coking wastewater discharge standards. For this purpose, it is investigated the treatment process and selected the bacteria to degradate the phenolic substances in this thesis. The details is as follows:1. It theoretically discusses the necessity and feasibility of constructing gene engineering bacteria to degrade the coking wastewater effectivly. The capacity of activated sludge strains isolated to degrade the coking wastewater is often limited. The use of genetic technique for genetic transformation strains obtained can significantly increase the degradation enzyme activity and expand the scope of the degradation substrate. The phenolic compounds has higher degradation rate than nitrogen heterocyclic compounds in the coking wastewater during the microbial degradation process, while gene engineering bacteria reduce the antagonism among microorganisms, increase the degradation efficiency and get the double degradation of phenolic compounds and heterocyclic substances.2. Activity sludge from Taiyuan Coal Gasification Company's second coke plant is served as the bacterial source. Two training programs are developed bydifferent liquid medium, selective enrichment culture technology and the increase of phenol concentration. In the screening program (1), when phenol concentration is 1800 mg/L we get phenol degradation bacterium A1; in the screening program (2) when phenol concentration is 2000 mg/L we get phenol degradation bacterium C1, D2 and D3. These four strains screened have higher tolerance to phenol and take phenol as sole carbon source. 3. By the means of biomass staining, colony morphology observation, investigation of physiological and biochemical characteristics, these four phenol degrading bacteria were identified. A1 is as Sphaerobacter, C1 as Acinetobacter, D2 as Comamonas and D3 as Novosphingobium. Biotechnology company (Genolab Biotech Co.,Ltd.) was commissioned to do 16s rDNA molecular identification, C1 is Acinetobacter baumannii, D2 is Comamonas testosteroni and D3 is Novosphingobium naphthalenivorans.4. Four strains in different phenol concentration 500mg/L, 1000mg/L, 1500mg/L and 2000mg/L were determined the efficiency of phenol degradation. It was found that strain D2 had better results than the other three. D2 strain was further selected and studied the environmental factors on the rate of phenol degradation experiments, such as temperature, pH and rotation speed. The optimization of environmental conditions was.In summary, four strains of phenol degrading bacteria has been screened out during this study. All of them have higher tolerance and better degradation ability for phenol. All of these can be as the candidate recipient strain in constructing genetic engineering strain using in the coking wastewater degration. In addition to, Strain A1 is not a common strain as usually we used, that means it can enrich microbial resources for phenol cracking. Through the environmental impact experiments, the environmental conditions of strain D2 have been optimized in the process of degradation of phenol. It provides data as reference for coking wastewater treatment by activated sludge.