Microbial community study in a petrochemical industry wastewater treatment system by PCR-DGGE

To improve the efficiency of petrochemical wastewater purification, the relationship between bacterial community structure and pollutants loading/degrading rates in A/O process for petrochemical wastewater treatment was investigated by denaturing gradient gel electrophoresis (DGGE) of the 16S rRNA gene fragments amplified by polymerase chain reaction (PCR). Results show that while the influent COD and NH4+-N concentrations are 425.92-560 mg/L and 64-100 mg/L respectively, the corresponding average concentrations of the effluent are 160 mg/L and 55 mg/L, which are 1.6 and 3.6 times more than the national standards respectively. It demonstrates that the performance of pollutants removal process is inefficient. The analysis of PCR-DGGE profile indicates that the bacterial community structure of the activated sludge in A/O system is species-rich but unstable, and the highest and the lowest similarity coefficients are 36% and 6.25% respectively, which shows that remarkable community structure evolution exists in the system. The variation of bacterial community structure and pollutants loading influences the removal efficiency of pollutants obviously, and relatively stable community structure leads to the stable operational performance of biological wastewater treatment system.