Kinetic modelling of in situ treatment of petroleum hydrocarbon contaminated soil using bone char and NPK fertilizers

Abstract This study investigates the effectiveness of bone char (organic) and inorganic nitrogen, phosphorous, and potassium (NPK) fertilizers as stimulants in the degradability of petroleum hydrocarbon contaminants on soil. The physicochemical properties of the hydrocarbon sludge were used to assess the effectiveness of this process over an 8-week period using 0.5–3.5 kg mass of each fertilizer at different experiments. A first order kinetic model was used to estimate the rate of degradation of the total hydrocarbon content (THC) and total organic carbon (TOC) contaminants and the half-life of the remediation process. The microbial population within the period was also determined. The p-value (p < 0.05) indicated that these fertilizers were effective in degrading these contaminants on the soil, because of the significant difference between the treated and the control soil samples. A direct relationship was observed between with the mass and performance of the fertilizers. With 3.5 kg mass of the fertilizers, rate constants of 0.018 and 0.019 d− 1 were obtained for the removal of the THC and TOC contaminants, respectively, using the bone char fertilizer, whereas NPK fertilizer gave rates of 0.03 and 0.023 d− 1 respectively. The performance of the NPK fertilizer is attributable to its nitrogen and phosphorous content. The model adequately described the process and showed the effectiveness of both fertilizers in the remediation process.