Wet air oxidation of leachate containing emulsifed and solubilized hydrocarbons from crude oil‑contaminated soil

The present research work is focussed on the treatment of leachate generated from crude oil-contaminated soil sites using wet air oxidation as an advanced oxidation process. The factors afecting the wet air oxidation (WAO) process, viz. temperature, pressure and time of treatment were optimized using central composite design and response surface methodology. The signifcant factors were optimized to maximize % COD removal from the leachate. The linear efects of pressure and temperature (p=0.000); the square efects of pressure (p=0.019) and time (p=0.007) and the interaction efect of temperature–pressure (p=0.002) were found to be signifcantly governing the % COD removal. The maximum COD removal of 76% was obtained at temperature=244 °C, time=30 min and pressure=5 bar. Further, the biodegradability index (BOD5/COD) increased from 0.14±0.007 of the untreated leachate to 0.48±0.02 of the wetox-treated leachate. Moreover, the degradation of recalcitrant hydrocarbons in initial leachate by WAO treatment was confrmed using GC–MS analysis.