Abstract: The microbial treatment of petroleum-contaminated groundwater was carried out in Zhipo, China. Ten strains of degradation bacteria were isolated from petroleum contaminated land. The experimental result showed that the degradation efficiency of single strain ranged from 20 to 50%; and that of mixed strains MZ9402 was 71.4%. In a simulation reactor contained with petroleum contaminated groundwater, the degradation efficiency of MZ9402 was up to 53.1% when the concentration of injected bacteria was 10⁶ individuals·ml^-1 . Field scale experiments showed that when the concentration of injected bacteria MZ9402 was 10⁹ individuals·ml^-1, a more stable microbial zone could be formed in the waterflow section after 11 days, and 35% of the petroleum could be degraded. According to the tentative identification. no mutation was occurred for the injected MZ9402 strains.

Key words: Groundwater, Petroleum contamination, Microbial treatment