Enhanced ex-situ bioremediation of soil contaminated with petroleum refinery waste effluents by biostimulation through electrokinetics and inorganic fertilizer
Ex situ bioremediation is an attractive and often cost-effective technology for the clean-up of organics-contaminated sites; however, it often requires extended treatment time under field conditions. Electrokinetic bioremediation is an emerging technology to remediate organic-contaminated soil. Thus, the objective of this study was to investigate the feasibility and effectiveness of using electrical biostimulation processes to enhance ex-situ bioremediation of soils contaminated with organic pollutants. The effect of different applied voltages (0.33 – 1.0 V/cm) as well as the effect of inorganic (NPK) fertilizer on the electrokinetic bioremediation of soil was evaluated. A bench-scale uniform electrokinetic system was developed for this purpose and tested by using a sandy loam soil spiked with petroleum refinery waste effluent having total organic compound (TOC) as model organic pollutant. The results demonstrated that the application of a low direct current (voltage) could be an effective strategy to accelerate the movement and ex situ biodegradation or removal of TOC in the soil. At the application of 0.33, 0.67 and 1.0 V/cm voltage, electricity biostimulation correspondingly and averagely remove 65.7%, 70% and 73.3% of TOC from soil in only 15 days without nutrient (NPK fertilizer) application; while with nutrient application, electricity biostimulation correspondingly and averagely removed 71.8%, 77.4% and 81.6% of TOC from soil. Thus, bioremediation of soil contaminated with petroleum refinery waste effluents can be enhanced by electrokinetics and the rate of TOC biodegradation or removal relatively increased with increased specific voltage application. The electrokinetic bioremediation of soil can further be enhanced or accelerated with the addition of nutrient in the form of nitrogen, phosphorus and potassium (NPK). Small changes in soil pH and/or moisture were induced by the applied electric field.
Keywords: Bioremediation; Electrokinetics; NPK Fertilizer; Refinery Waste Effluents; TOC.