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Online monitoring of groundwater quality in shallow wells to detect faecal or organic pollution could dramatically improve understanding of health risks in unplanned peri-urban settlements. Microbial fuel cells (MFC) are devices able to generate electricity from the organic matter content in faecal pollution making them suitable as biosensors. In this work, we evaluate the suitability of four microbial fuel cell systems placed in different regions of a groundwater well for the low-cost monitoring of a faecal pollution event. Concepts created include the use of a sediment/bulk liquid MFC (SED/BL), a sediment/sediment MFC (SED/SED), a bulk liquid/air MFC (BL/Air), and a bulk liquid/bulk liquid MFC (BL/BL). MFC electrodes assembly aimed to use inexpensive, durable, materials, which would produce a signal after a contamination event without external energy or chemical inputs. All MFC configurations were responsive to a contamination event, however SED/SED and BL/Air MFC concepts failed to deliver a reproducible output within the tested period of time. BL/BL MFC and SED/BL MFCs presented an increase in the average current after contamination from -0.75 ± 0.35 μA to -0.66 ± 0.41 μA, and 0.07 ± 0.2 mA to 0.11 ± 0.03 mA, respectively. Currents produced by the SED/BL MFC (SMFC) were considerably higher than for the BL/BL MFCs, making them more responsive, readable and graphically visible. A factorial design of experiments (DOE) was applied to evaluate which environmental and design factors had the greatest effect on current response in a contamination event. Within the ranges of variables tested, salinity, temperature and external resistance, only temperature presented a statistically significant effect (p = 0.045). This showed that the biosensor response would be sensitive to fluctuations in temperature but not to changes in salinity, or external resistances produced from placing electrodes at different distances within a groundwater well.

Bioelectrochemical metal remediation and recovery of Au 3+ , Co 2+ and Fe 3+ metal ions.

Photocatalysis has shown the ability to inactivate a wide range of harmful microorganisms with traditional use of chlorination. Photocatalysis combined with applied bias potential (photoelectrocatalysis) increases the efficiency of photocatalysis and decreases the charge recombination. This work examines the inactivation of fecal coliform bacteria present in real urban wastewater by photoelectrocatalysis using nanoparticulated films of TiO and TiO/Ag (4%w/w) under UV light irradiation. The catalysts were prepared with different thicknesses by the sol-gel method and calcined at 400°C and 600°C. The urban wastewater samples were collected from the sedimentation tank effluent of the university sewage treatment facility. The rate of bacteria inactivation increases with increasing the applied potential and film thicknesses; also, the presence of silver on the catalyst surface annealed at 400°C shows better inactivation than that at 600°C. Finally, a structural cell damage of Escherichia coli (DH5α), inoculated in water, is observed during the photoelectrocatalytic process.