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ABSTRACT
This study aimed at optimizing the bioremediation of crude oil-contaminated soil using a mix of corn cobs as biochar and NPK 15:15:15, employing a Box-Behnken design with response surface methodology (RSM). Soil pollution from crude oil has emerged as a serious global environmental and human health issue, with large amounts of used oil discharged into the environment without proper treatment (Wu et al., 2016). To carry out this experiment, materials including uncontaminated soil, crude oil, corn cobs, NPK 15:15:15 fertilizer, and chemicals like hexane were collected. The specific density of crude oil was determined using a density bottle, and biochar was prepared from corn cobs through carbonization. The experimental setup involved contaminating soil with crude oil, adding biochar and NPK 15:15:15 mix to the bioreactors, and conducting bioremediation under aerobic conditions. The residual hydrocarbon content (RHC) in the soil was determined by extraction using hexane and measuring absorbance. This study utilized a Box-Behnken design and response surface methodology to optimize the bioremediation process and analyze results. A total of 29 experimental runs were carried out. The experiments achieved a minimal residual hydrocarbon content of 141.26mg/Kg and heavy metal concentration of 0.0079mgL and this was achieved at Run 10 (i.e. at Crude oil concentration of 85.6ml, , Biochar dosage of 40g, NPK 15:15:15 dosage of 100g, and 4 remediating weeks) with R2 values of 0.9883 and 0.9402 for RHC and heavy metal concentration, showing the effectiveness of biochar and NPK 15:15:15 mix in removing crude oil from contaminated soil. The optimal conditions obtained from the experimental design using Box-Behnken are 51.7041mg/Kg residual hydrocarbon content (RHC) and 0.00639447mg/L heavy metal concentration.
