Industrial wastewater treatment with a bioelectrochemical process: assessment of depuration efficiency and energy production

Abstract Development of renewable energy sources, efficient industrial processes, energy/chemicals recovery from wastes are research issues that are quite contemporary. Bioelectrochemical processes represent an eco-innovative technology for energy and resources recovery from both domestic and industrial wastewaters. The current study was conducted to: (i) assess bioelectrochemical treatability of industrial (dairy) wastewater by microbial fuel cells (MFCs); (ii) determine the effects of the applied organic loading rate (OLR) on MFC performance; (iii) identify factors responsible for reactor energy recovery losses (i.e. overpotentials). For this purpose, an MFC was built and continuously operated for 72 days, during which the anodic chamber was fed with dairy wastewater and the cathodic chamber with an aerated mineral solution. The study demonstrated that industrial effluents from agrifood facilities can be treated by bioelectrochemical systems (BESs) with >85% (average) organic matter removal, recovering power at an observed maximum density of 27 W m−3. Outcomes were better than in previous (shorter) analogous experiences, and demonstrate that this type of process could be successfully used for dairy wastewater with several advantages

Role of Operating Conditions on Energetic Pathways in a Microbial Fuel Cell

AbstractThe electric performance of a Microbial Fuel Cell (MFC) fed with swine manure, and specifically the interactions between different coexisting bacterial populations are examined in relationship to the Organic Loading Rate (OLR) and External Resistance applied to the cell. Feasibility of swine manure treatment using MFCs was already demonstrated by previous studies, however low Coulombic efficiencies were attained due to a competing methanogenic degradation occurring in the same cells. External resistance (Rext) and Organic Loading Rate have been identified as two of the key parameters affecting the balance between exoelectrogenic and methanogenic bacterial populations in a MFC system; despite this, virtually no attention had been paid to the study of OLR influence on MFCs performance. This study evaluates the performance of a MFC, treating swine manure, in this perspective, demonstrating that high OLRs (up to 11.2kg COD m3/d) have a limiting effect on MFCs electrochemical losses, and increase absolute values of ORR (4.6kg COD m3/d) and current production (14.9mA). On the other hand, adoption of low OLR (as low as 0.7kg COD m3/d) translates in an increase of both organic matter removal efficiency (52%) and Coulombic efficiency (higher than 70%). These improvements can be directly connected with the shifting balance between exoelectrogenic and methanogenic biomass populations, as confirmed by the cell's anode off-gas analysis. Hence, by adopting the appropriate design value of ORL and operating conditions, the MFC's biofilm exoelectrogenic population fraction, and thus its overall activity, can be improved considerably

Simplified modelling of nonlinear electromethanogenesis stack for power-to-gas applications

Bioelectrochemical systems performing electromethanogenesis (EMG-BES) represent an emerging technology for Power-to-gas as well as wastewater treatment. Moreover, EMG-BES can be used as a high-capacity energy storage system to absorb surplus energy in the electrical grid. This paper presents a modelling approach, which is based on building an equivalent electric circuit of the EMG-BES, which can be used to emulate static and dynamic non-linear behaviour of EMG-BES for different input voltages, which is advantageous if compared to other existing models. This model is a suitable choice for future studies in the development of the electric converters for EMG-BES plants connected to the electrical grid. The proposed model consists of practical and commercial elements, including capacitors, resistors, voltage sources, and a diode. The modelling of non-linear behaviour is achieved by adding a diode to the model. Four simple tests were performed to determine the equivalent circuit parameters in a medium-scale EMG-BES prototype. This prototype was built by stacking 45 cells together and connecting them in parallel, and it was long-term operated and tested under different electric inputs to determine the model parameters. A comparative study was finally conducted as reported in this paper in order to validate the proposed model against experimental results and values collected with other models.The research leading to these results has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 712949 (TECNIOspring PLUS) and from the Agency for Business Competitiveness of the Government of Catalonia. Also, this work has been supported by the Spanish Ministry of Economy and Competitiveness under the projects RTI2018-100921-BC21. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect those of the host institutions or funders. The authors wish to acknowledge the Leitat collaborators who took part in Power2Biomethane project, which was financially supported by the Spanish Ministry of Economy and Competitiveness (RTC-2016- 5024-3, 2016).Peer ReviewedPostprint (author's final draft

Design, operation, modeling and grid integration of power-to-gas bioelectrochemical systems

Peer ReviewedPostprint (published version

An Integrated Mathematical Model of Microbial Fuel Cell Processes: Bioelectrochemical and Microbiologic Aspects

Microbial Fuel Cells (MFCs) represent a still relatively new technology for liquid organic waste treatment and simultaneous recovery of energy and resources. Although the technology is quite appealing due its potential benefits, its practical application is still hampered by several drawbacks, such as systems instability (especially when attempting to scale-up reactors from laboratory prototypes), internally competing microbial reactions, and limited power generation. This paper is an attempt to address some of the issues related to MFC application in wastewater treatment with a simulation model. Reactor configuration, operational schemes, electrochemical and microbiological characterization, optimization methods and modelling strategies were reviewed and have been included in a mathematical simulation model written with a multidisciplinary, multi-perspective approach, considering the possibility of feeding real substrates to an MFC system while dealing with a complex microbiological population. The conclusions drawn herein can be of practical interest for all MFC researchers dealing with domestic or industrial wastewater treatment