Characteristics of organic carbon metabolism and bioremediation of petroleum-contaminated soil by a mesophilic aerobic biopile system

Abstract

An innovative mesophilic aerobic biopile technology was explored to improve the bioremediation efficiency of petroleum-contaminated soil. Under the suitable soil conditions (C:N:P at 100:5:1 and soil moisture content at 18%), the soil pH was hold in the range of 7.4 to 6.8 throughout the bioremediation process, the mesophilic (30 °C-40 °C) and forced aeration (3 h-on/1 h-off) conditions were the critical factors to enhancing petroleum biodegradation. The consumption of bioavailable organic carbon (BAC) which was one of the most important factors regulating microbial metabolism, was positively related (R2 = 0.85, 40 °C) with the rate of petroleum removal. The 50% threshold of BAC could be regarded as the signal for supplementing the soil nutrients in the mesophilic aerobic biopiles to favor petroleum removal. The optimal conditions (40 °C, 3 h-on/1 h-off) maximized the utilization of BAC, promoted the petroleum degradation, and remained the microbial abundance and community composition stable to the greatest extent. In addition, the accumulation of aliphatic acids affected the microbial activity, which limited the efficiency of petroleum degradation to a certain extent. Jointly considering the energy consumption, time cost and soil conditions maintenance, a cost-effective biopile technology was obtained by temperature and aeration regulation and BAC supplementation, which could be applied to engineering application.