Sediment microbial fuel cells (SMFC) are bioelectrochemical systems that can use different wastes for energy production. This work studied the implementation of nanoparticles (NPs) of α-FeOOH (goethite, which is well-known as a photoactive catalyst) in the electrodes of an SMFC for its potential use for dye removal. The results obtained demonstrate the feasibility of the NPs activation with the electrical potential generated in the electrodes in the SMFC instead of the activation with light. The NPs of α-FeOOH were synthesized using a hydrothermal process, and the feasibility of a conductive bio-composite (biofilm and NPs) formation was proven by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and electrochemical techniques. The improvement of the power density in the cell was more than twelve times higher with the application of the bio-composite, and it is attributed mostly to the presence of NPs. The results also demonstrate the NPs effect on the increase of the electron transfer, which resulted in 99% of the COD removal. The total electrical energy produced in 30 days in the SMFC was 1.2 kWh based on 1 m² of the geometric area of the anode. The results confirm that NPs of α-FeOOH can be used to improve organic matter removal. Moreover, the energy produced due to its activation through the potential generated between the electrodes suggests the feasibility of its implementation for dye removal.

Microalgae can grow in alternative media, such as wastewater, since they can consume the nutrients present in it, generating high productivity of biomass and high-value compounds, such as fatty acids, carbohydrates, and pigments. This research aimed to optimize the concentration of ammonium, phosphates, and luminosity for the cultivation of the microalgae Leptolyngbya sp. and Chlorella sp. in synthetic wastewater, to study the consumption of nutrients and their influence on the biomass and lipids yield, which can be used for the biodiesel production. Different culture conditions were tested, such as: nutrient stress, photo-stress, excess nutrients, as well as under heterotrophic and mixotrophic conditions. The results indicated an optimal point for the consumption of ammonium and phosphates of Chlorella sp., In the concentration of 58.82 mg L⁻¹, ammonium, 30.17 mg L⁻¹, phosphates and 3645.54 lux of illumination: while for Leptolyngbya sp., in the concentrations of 58.82 mg L⁻¹, ammonium, 30.17 mg L⁻¹, phosphates and 3645.54 lux of illumination. Leptolyngbya sp. presented the highest lipid and biomass concentrations.