Modified Fenton oxidation of polycyclic aromatic hydrocarbon (PAH)-contaminated soils and the potential of bioremediation as post-treatment

This work focuses on the remediation of polycyclic aromatic hydrocarbon (PAH)-contaminated soil using modified Fenton (MF) treatment coupled with a novel chelating agent (CA), a more effective technique among currently available technologies. The performance of MF treatment to promote PAH oxidation in artificially contaminated soil was investigated in a packed column with a hydrogen peroxide (H2O2) delivery system simulating in-situ soil flushing which is more representative of field conditions. The effectiveness of process parameters H2O2/soil, Fe3 +/soil, CA/soil weight ratios and reaction time were studied using a 24 three level factorial design experiments. An optimised operating condition of the MF treatment was observed at H2O2/soil 0.05, Fe3 +/soil 0.025, CA/soil 0.04 and 3 h reaction time with 79.42% and 68.08% PAH removals attainable for the upper and lower parts of the soil column respectively. The effects of natural attenuation and biostimulation process as post-treatment in the remediation of the PAH-contaminated soil were also studied. In all cases, 3-aromatic ring PAH (phenanthrene) was more readily degraded than 4-aromatic ring PAH (fluoranthene) regardless of the bioremediation approach. The results revealed that both natural attenuation and biostimulation could offer remarkable enhancement of up to 6.34% and 9.38% in PAH removals respectively after 8 weeks of incubation period. Overall, the results demonstrated that combined inorganic CA-enhanced MF treatment and bioremediation serves as a suitable strategy to enhance soil quality particularly to remediate soils heavily contaminated with mixtures of PAHs.

► Modified Fenton oxidation of PAHs in soil column experiments was optimised.
► Mild reagent concentration that is less costly was required at optimised condition.
► Natural attenuation as post-treatment promoted further PAH removal of up to 6.34%.
► Biostimulation as post-treatment promoted further PAH removal of up to 9.38%.
► Modified Fenton-bioremediation is a suitable strategy to enhance soil quality.