Respirometry for assessing the biodegradation of petroleum hydrocarbons

The respiration method using the Micro-Oxymax (R) respirometer was applied to evaluate the bioremediation potential of hydrocarbon-contaminated soils in two biopiles at the oil refinery in Czechowice-Dziedzice, Poland. In biopiles 1 and 2, two different technologies, i.e., enhanced (engineered) bioremediation and monitored natural attenuation (MNA) were used, respectively. In biopiles 1 and 2, the bioremediation process lasted 6 years and 8 months, respectively. The biodegradation of petroleum hydrocarbons was evaluated on the basis of CO2 production and O-2 uptake. The CO2 production and O-2 consumption rates during hydrocarbon biodegradation were calculated from the slopes of cumulative curve linear regressions. The results confirmed the hydrocarbon biodegradation process in both biopiles. However, in biopile 2 the process was more effective compared to biopile 1. In biopile 2, the O-2 consumption and CO2 production means were 3.37 and 2.4 milliliters per kilogram of soil (dry weight) per minute, respectively. Whereas, in biopile 1, the O-2 consumption and CO2 production means were 1.52 and 1.07 milliliters per kilogram of soil (dry weight) per minute, respectively. The mean biodegradation rate for biopile 2 was two times higher - 67 mg hydrocarbons kg d.w.(-1)day(-1) compared with biopile 1, where the mean was 30 mg hydrocarbons kg d.w.(-1)day(-1). The results were correlated with petroleum hydrocarbon concentrations and microbial activity measured by dehydrogenase assay.