No abstract

A submersible microbial fuel cell (SMFC) was utilized to treat sewage sludge and simultaneously generate electricity. Stable power generation (145 +/- 5 mW/m2, 470 omega) was produced continuously from raw sewage sludge for 5.5 days. The maximum power density reached 190 +/- 5 mW/m2. The corresponding total chemical oxygen demand (TCOD) removal efficiency was 78.1 +/- 0.2% with initial TCOD of 49.7 g/L. The power generation of SMFC was depended on the sludge concentration, while dilution of the raw sludge resulted in higher power density. The maximum power density was saturated at sludge concentration of 17 g-TCOD/L, where 290 mw/m2 was achieved. When effluents from an anaerobic digester that was fed with raw sludge were used as substrate in the SMFC, a maximum power density of 318 mW/m2, and a final TCOD removal of 71.9 +/- 0.2% were achieved. These results have practical implications for development of an effective system to treat sewage sludge and simultaneously recover energy.

Overview of challenges and opportunities in microbial fuel cells for in-field operation.

The growing use of herbicides in agriculture poses increasing concerns on the pollution of water systems worldwide. To be able to assess the presence of these compounds in waters and limit their impact on human health and ecosystems, the development of effective in-situ monitoring tools is key. Yet, many existing sensing technologies are not suitable for in-situ and remote applications, due to challenges in portability, durability, cost, and power requirements. In this study, we explore for the first time the use of an algae-assisted cathode in a photosynthetic microbial fuel cell (p-MFC) as a self-powered dissolved oxygen probe for herbicides detection in water. The cathode is enriched with the alga Scenedesmus obliquus and two different electrode materials are tested, graphite felt and indium tin oxide, which differ in porosity, surface roughness, and transparency. Despite the much larger specific surface area of graphite felt compared to indium tin oxide, the current generated under light was only 10 times larger (109 ± 2 µA vs. 10.5 ± 0.6 µA) and eight times larger in the dark (37 ± 5 vs. 4.2 ± 0.6 µA). By generating a current output that correlates with the dissolved oxygen in the catholyte, the resulting p-MFCs could detect the EU legal atrazine concentration limit of 0.1 µg L −1. The use of graphite felt led to shorter response times and better sensitivity, as a result of the greater current baseline. In both cases, the current baseline was recovered after exposure of the sensor to frequent toxic events, thus showing the resilience of the cathodic biofilm and the potential of the p-MFCs for early warnings of herbicides pollution in water.