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

Sustainable processing of dairy wastewater: Long-term pilot application of a bio-electrochemical system

Demographic growth, increasing food demand and non-renewable fuels depletion require new sustainable industrial approaches in all areas of the agro-farming sector. Microbial fuel cells (MFCs) could represent an eco-innovative technology for energy and resources recovery from agrofood processes wastewaters. This study was conducted to: (i) assess the bioelectrochemical treatability of dairy wastewater by means of MFCs; (ii) determine the effects of the organic loading rate (OLR) on MFCs performance; (iii) evaluate the reactors’ overpotentials, and identify possible strategies oriented to their reduction. For this purpose, two replicate MFCs were built and continuously operated for 65 days. The anode chamber was fed with undiluted dairy wastewater at 1 L d−1. An aerated mineral medium was fed to the cathode chamber with the same flow-rate. The study demonstrated that these types of industrial effluents can be treated by MFCs with 82% (average) organic matter removal, recovering a maximum power density of 26.5 W m−3. Coulombic efficiency (CE) of the lab-scale reactors decreased by increasing the OLR (organic loading rate). The highest CE was found to be 24% at a OLR of 3.7 kg COD m−3 d−1. MFCs energy losses were mainly due to cathode reaction (34–39% of total loss) and ionic transport through the membrane (27–33%). Achieved results were better than previously reported MFC-experiences dealing with dairy (or similar) wastewater treatment

Sustainability of decentralized wastewater treatment technologies

In many Countries, small communities are required to treat wastewater discharges to increasing standards of lesser environmental impacts, but must achieve that goal at locally sustainable costs. While biological membrane treatment (membrane bio-reactors (MBRs)) is quickly becoming the industry standard for centralized wastewater treatment plants, and would also be ideally suited also for small plants potentially subject to relatively large hydraulic load variations, its investment and operating costs are usually high for that class of applications. Consequently, small treatment plants are generally configured as anoxic or aerated biological tanks with little sedimentation, making them quite susceptible to hydraulic loads transient and sludge quality changes. As an alternative, Constructed Wetlands Systems (CWSs) are gradually and successfully being introduced in many Countries. CWSs are designed to utilise the natural functions of wetland vegetation, soils and their microbiological populations to treat wastewater. Pretreatment occurs by filtration and settling, followed by bacterial decomposition in a natural-looking lined marsh. A new technology, a new type of membrane-like aerobic reactor initially designed for the degradation of hydrocarbon-derived groundwater contaminants, was recently tested for treating domestic, with performance similar to that of MBRs. Examples from the above applications are illustrated and compared in this paper. The paper also discusses merits and drawbacks of the various illustrated technologies, in view of their sustainability potential, and according to the new development paradigms for urban water systems, that encourage the development of local water-cycle clusters with local reuse and recycle of the resource, and possible local recovery of energy and/or materials