Optimization of field scale biopiles for bioremediation of petroleum hydrocarbon contaminated soil at low temperature conditions by response surface methodology (RSM)

• The study successfully assessed and compared biodegradation of TPHs under cold weather conditions.
• A factorial design was employed for statistical analysis and regression of data.
• Response surface methodology was used to optimize the process.

Ex-Situ Bioremediation has been increasingly viewed as an appropriate remediation technology for hydrocarbon contaminated soils under cold climates conditions in countries like Canada. A response surface methodology (RSM) based on a factorial design was performed to investigate and optimize the effects of the microbial consortia application rate and amount of mature compost amendment on the TPH removal (964 μg g−1 initial concentration). 18 field-scale biopiles (16 m3 each) were constructed, maintained and subjected to different microbial consortium and mature compost application rates under cold climate conditions over a period of 94 days. TPHs removal rates in the range of 74–82% was observed in the treatments setups where mature compost and microbial consortia were used simultaneously, compared to an average 48% of TPHs removal in control setup.The interaction between these two factors were studied and modelled using a statistical regression model, which showed that the microbial consortia application rate, the mature compost amendment and their interactions had a significant effect on TPHs degradation with a coefficient of determination (R2) of 0.88. Furthermore, using a numerical optimization approach, the optimum rates predicted via RSM were estimated at 4.1 ml m−3 and 7% for microbial consortia and compost application rates to obtain a maximum TPH removal of 90.7%.