Study On The Isolation Of Superior Strain For O-xylene And Its Bioaugmentation On Coking Wastewater

Coking wastewater mainly from the coking produced in the process of surplus ammonia water, containing pollutants including phenols, heterocyclic or polycyclic aromatic hydrocarbons and benzene series. These compounds have a certain or strong risk of biological toxicity to microbe which can inhibit its growth, and the traditional biological treatment doesn’t eliminate the residue completely and it cannot satisfy the needs for environment protection. In recent years, many experts and scholars did substantive research in the field of coking wastewater by adopting the bioaugmentation technology and achieved significant progress. But majority of the former research relate only to phenols and N- heterocyclic and few deal with benzene series.In this study, o-xylene was used as the target pollutant and one high efficiency bacterium was isolated from coking-wastewate-contaminated soil. First, morphological observation, gram stain, physiological and biochemical properties and 16 S rDNA sequence were analyzed to identify the strain. Then, the growth and degradation conditions, the degradation kinetics and the range of substrate degradation were investigated. Finally, compound bacteria with the strain and the other six high efficiency strains were built, then its growth characteristics and bioaugmentation in coking wastewater were discussed. The main research conclusions of this study are as follows:1. O-xylene was used as the target substrate and a high efficiently degradation bacterium OX5 was isolated. The strain was identified as Pseudomonas aeruginosa sp. by physiological and biochemical characteristics test and 16 S rDNA sequence identification.2. The optimum temperature, initial pH, shaker rotary speed and bacterialload for OX5 was 30~35 ℃, pH 7.0~8.0, 150 r/min and inoculating quantity 2%, respectively. O-xylene started to inhibit OX5 proliferation when its mass concentration reached up to 200 mg/L. The degradation of o-xylene on strain OX5 follows the Monod kinetic equation, and when the initial o-xylene mass concentration ρ?64.32 mg/L, the degradation rate was 43.29 mg/(L·h).3. Compound bacteria which composed of strains for phenols(F、LF1)、strains for N- heterocyclic(Q、P3)、strain for alkane C16、strain for naphthalene N、strain for o-xylene OX5 at the ratio of LF1:P3:C16:F:OX5=2:2:1:2:1 had the highest degradation rate to COD of coking wastewater. The optimum temperature, initial pH and shaker rotary speed was 30 ℃, pH 7.0~8.0 and 200 r/min.4. The removal rate of COD increased from 48.5 % to 58.3% with glucose, however sucrose hardly had an effect on it. It had a best influence on the removal of COD while adding peptone as nitrogen source, the removal rate was up to 54.2%, and the effect of adding carbamide or KNO3 is less than using peptone or(NH4)2SO4.5. Comparing with the single strain, compound bacteria had a wider range of substrate degradation and the larger dehydrogenase activity, and could increase the removal rate of COD by 19%~29%. The COD could be removed 87.3% within 72 h on “compound bacteria+ activated sludge” in flask-shaking.