Impact of chemical oxidation on indigenous bacteria and mobilization of nutrients and subsequent bioremediation of crude oil-contaminated soil

After stepwise Fenton pre-oxidation at a low H2O2 concentration (225 × 4), the remaining indigenous bacterial populations reached their peak (4.8 ± 0.17 × 106 CFU/g), the nutrients were mobilized rapidly, and the subsequent bioremediation of crude oil was improved (biodegradation efficiency of 35%). However, after stepwise Fenton pre-oxidation at a high H2O2 concentration (450 × 4), only 3.6 ± 0.16 × 103 CFU/g of indigenous bacteria remained, and the indigenous bacteria that degrade C15-C30 alkanes were inhibited. The nutrient mobilization was then highly limited, and only 19% of total petroleum hydrocarbon was degraded. Furthermore, the recovery period after the low H2O2 concentration stepwise Fenton pre-oxidation (225 × 4) was less than 20 days, which was 20-30 days shorter than with the other pre-oxidation treatments. Therefore, stepwise Fenton pre-oxidation at a low H2O2 concentration protects indigenous bacterial populations and improves the nutrient mobilization and subsequent bioremediation.