Novel trickling microbial fuel cells for electricity generation from wastewater.

There are two main challenges associated with the scale-up of air-cathode microbial fuel cells (MFCs): performance reduction and cathode leakage/flooding. In this study, a novel 13.4 L reactor that contains 4 tubular MFCs was designed and operated in a trickling mode for 65 days under different conditions.

Accelerated tests for evaluating the air-cathode aging in microbial fuel cells.

Air-cathode stability is a key factor affecting the feasibility of microbial fuel cells (MFCs) in applications. However, there is no quick and effective method to evaluate the robustness and durability of the MFC air cathodes. In this study, a three-phase decrease of power density was observed in multiple MFCs that have been operated for about a year.

Millimeter scale electron conduction through exoelectrogenic mixed species biofilms.

The functioning of many natural and engineered environments is dependent on long distance electron transfer mediated through electrical currents. These currents have been observed in exoelectrogenic biofilms and it has been proposed that microbial biofilms can mediate electron transfer via electrical currents on the centimeter scale. However, direct evidence to confirm this hypothesis has not been demonstrated and the longest known electrical transfer distance for single species exoelectrogenic biofilms is limited to 100 μm.

Redox Conductivity of Current-Producing Mixed Species Biofilms.

While most biological materials are insulating in nature, efficient extracellular electron transfer is a critical property of biofilms associated with microbial electrochemical systems and several microorganisms are capable of establishing conductive aggregates and biofilms. Though construction of these conductive microbial networks is an intriguing and important phenomenon in both natural and engineered systems, few studies have been published related to conductive biofilms/aggregates and their conduction mechanisms, especially in mixed-species environments. In the present study, current-producing mixed species biofilms exhibited high conductivity across non-conductive gaps.

Enhanced performance and mechanism study of microbial electrolysis cells using Fe nanoparticle-decorated anodes.

Anode properties are critical for the performance of microbial electrolysis cells (MECs). In the present study, Fe nanoparticle-modified graphite disks were used as anodes to investigate the effects of nanoparticles on the performance of Shewanella oneidensis MR-1 in MECs. Results demonstrated that the average current densities produced with Fe nanoparticle-decorated anodes up to 5.

Nanoparticle decorated anodes for enhanced current generation in microbial electrochemical cells.

The development of highly efficient anode materials is critical for enhancing the current output of microbial electrochemical cells. In this study, Au and Pd nanoparticle decorated graphite anodes were developed and evaluated in a newly designed multi-anode microbial electrolysis cell (MEC). The anodes decorated with Au nanoparticles produced current densities up to 20-fold higher than plain graphite anodes by Shewanella oneidensis MR-1, while those of Pd-decorated anodes with similar morphologies produced 50-150% higher than the control.

Quantification of the internal resistance distribution of microbial fuel cells.

Identifying the limiting factors in a microbial fuel cell (MFC) system requires qualifying the contribution of each component of an MFC to internal resistance. In this study, a new method was developed to calculate the internal resistance distribution of an MFC. Experiments were conducted to identify the limiting factors in single-chamber MFCs by varying the anode surface areas, cathode surface areas, and phosphate buffer concentrations.

Hydrogen production using single-chamber membrane-free microbial electrolysis cells.

Microbial electrohydrogenesis provides a new approach for hydrogen generation from renewable biomass. Membranes were used in all the reported microbial electrolysis cells (MECs) to separate the anode and cathode chambers. To reduce the potential losses associated with membrane and increase the energy recovery of this process, single-chamber membrane-free MECs were designed and used to investigate hydrogen production by one mixed culture and one pure culture: Shewanella oneidensis MR-1.

Sustainable power generation in microbial fuel cells using bicarbonate buffer and proton transfer mechanisms.

Phosphate buffer solution has been commonly used in MFC studiesto maintain a suitable pH for electricity-generating bacteria and/or to increase the solution conductivity. However, addition of a high concentration of phosphate buffer in MFCs could be expensive, especially for wastewater treatment. In this study, the performances of MFCs with cloth electrode assemblies (CEA) were evaluated using bicarbonate buffer solutions.

High-performance planar pH fluorosensor for two-dimensional pH measurements in marine sediment and water.

A new plate fluorosensor foil was developed for two-dimensional pH measurement in marine sediments and overlying waters. The fluorescent dye 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (HPTS) was covalently linked onto a transparent poly(vinyl alcohol) membrane backed by polyester sheet. Both excitation and emission bands of the immobilized HPTS showed large red shifts in comparison to HPTS in free solution.

Biodegradability of Atrazine, Cyanazine and Dicamba under methanogenic condition in three soils of China.

Persistence and degradation of the herbicides Atrazine, Cyanazine and Dicamba were measured in laboratory microcosms incubated under methanogenic condition using three soils of China. Results showed that Atrazine was more resistant to degradation than Cyanazine and Dicamba for the 300 days of incubation. Between 30% and 40% of the initially introduced chemicals were found to be not recoverable through solvent extraction of the incubated soils.

Relationship between structures of substituted indolic compounds and their degradation by marine anaerobic microorganisms.

Degradation of selected indolic compounds including indole, 1-methylindole, 2-methylindole, and 3-methylindole was assessed under methanogenic and sulfate-reducing conditions using the serum-bottle anaerobic technique and marine sediment from Victoria Harbour, Hong Kong as an inoculum. Our results showed that indole degradation was achieved in 28 days by a methanogenic consortium and 35 days by a sulfate-reducing consortium. During degradation under both conditions, two intermediates were isolated, purified and identified as oxindole and isatin (indole-2,3-dione) suggesting that both methanogenic and sulfate-reducing bacteria use an identical degradation pathway.