Enhanced degradation of phenanthrene and pyrene in freshwater sediments by combined employment of sediment microbial fuel cell and amorphous ferric hydroxide.

The degradation of phenanthrene and pyrene in freshwater sediment was investigated under three kinds of treatments (addition of amorphous ferric hydroxide to sediments, employment of sediment microbial fuel cell (SMFC), and the combination of ferric addition and SMFC employment). After 240 days of experiments, it was found that the combined treatment led to the highest removal efficiencies of phenanthrene (99.47 ± 0.15%) and pyrene (94.79 ± 0.63%), while the employment of SMFC could obtain higher removal efficiencies than Fe(III) addition. The combined approach improved potentials of phenanthrene and pyrene biodegradation in sediments under anaerobic pathways except methanogenic condition, and also stimulated humification of organic matters in sediments. At the end of experiments, ratios of humic acid to fulvic acid in sedimentary organic matters reached to 2.967 ± 0.240 in the combined treatment, and were only around 1.404-1.506 in the other treatments. Thus, organic matters in sediments in the combined treatment could adsorb tightly residual PAHs with less bioavailability. Considering both enhanced biodegradation and final sequestration of PAHs in sediments, the combined application of Fe(III) addition and SMFC employment offered a new promising remediation technology for contaminated sediments.