Degradation of petroleum hydrocarbons and characteristics of bacterial communities of sedimentary microbial fuel cell supplied with oil sludge

Sedimentary microbial fuel cell (SMFC) is a technology, which ensures a high pollution control, good performance in electricity production, and long term stability operation. Using this technology for the oily sludge treatment, the sludge separation can be effectively avoided while development of a new method for the sludge treatment is provided. In this work, a SMFC with oily sludge as anode substrate was constructed and operated for 21 days. The removal efficiency of chemical oxygen demand (COD) and total petroleum hydrocarbons (TPH) were 55.81 and 44.73%, respectively. The degradation efficiency of TPH was 10.1 times higher than the control that obtained by the common anaerobic degradation. The degradation rate of n-alkanes followed the order of high carbon number (> C27) > low carbon number ( medium carbon number (C21 ~ C26). The odd-even alkane predominance (OEP) increased, indicating that a high contribution of the alkanes with even number of carbon atoms whose degradation predominates. The OUT number, Shannon index, AEC index, and Chao1 index of the sludge treated with SMFC (YN2) are greater than those of the original sludge (YN1). In addition, the Simpson index YN2 is lower (0.10) than for YN1 (0.16), showing that the microbial diversity of sludge increased after SMFC treatment. The relative abundance of Chloroflexi, Bacteroidia increased significantly. In addition, Pseudomonadales appeared, pointing out that the microbial species and their abundance in sediments are essential for the degradation of the organic matter and electricity production.