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The aim of this study is to increase the electricity generation capacity of sediment microbial fuel cell (SMFC) using sewage sludge as a substrate source in anode media via an attractive electrode material. For this purpose, several electrochemical and molecular techniques have been employed to evaluate the performance of SMFC. The max power density and charge transfer resistance of SMFC running on sewage sludge were 187 mW/m2 and 84.7 Ω, respectively. The polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) analysis indicated that bacteria in anode biofilm belonged to the Clostridia, d‐proteobacteria, g‐proteobacteria, and b‐proteobacteria. Scanning electron microscopy and fluorescence in situ hybridization observations demonstrated that a viable biofilm was formed on the anode surface and the abundance of bacteria was significantly higher than archaea. Consequently, this study showed that sewage sludge could be used as a substrate in the anode media of SMFC for producing high power density.

Tetracycline (TC) in aqueous environment could be reductively degraded by using a hydrogen-based membrane biofilm reactor (H-MBfR) under denitrifying conditions as it provides an appropriate environment for the antibiotic-degrading bacteria in biofilm communities. This study evaluates the performance of H-MBfR for simultaneous removal of nitrate and TC, formation of degradation products of TC, and community analysis of the biofilm grown on the gas-permeable hollow fiber membranes. Hence, a H-MBfR receiving approximately 20 mg N/l nitrate and 0.5 mg/l TC was operated under different H pressures, hydraulic retention times (HRTs), and influent TC concentrations in order to provide various nitrate and TC loadings. The results showed that H-MBfR accomplished successfully the degradation of TC, and it reached TC removal of 80-95 % at 10 h of HRT and 6 psi (0.41 atm) of H gas pressure. TC degradation took placed at increased HRT and H pressures while nitrate was the preferred electron acceptor for most of the electrons generated from H oxidation used for denitrification. The transformation products of TC were found at part per billion levels through all the experiments, and the concentrations decreased with the increasing HRT regardless of H pressure. Analyses from clone library showed that the microbial diversity at the optimal conditions was higher than that at the other periods. The dominant species were revealed to be Betaproteobacteria, Acidovorax caeni, and Alicycliphilus denitrificans.

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