Evaluation of microbial electrolysis cells in the treatment of domestic wastewate

Wastewater can be an energy source and not a problem. This study investigates whether rapidly emerging bioelectrochemical technologies can go beyond working in a laboratory under controlled temperatures with simple substrates and actually become a realistic option for a new generation of sustainable wastewater treatment plants. The actual amount of energy available in the wastewater is established using a new methodology. The energy is found to be considerably higher than the previous measurement, or estimates based on the chemical oxygen demand with a domestic wastewater sample containing 17.8 kJ/gCOD and a mixed wastewater containing 28.7 kJ/gCOD. With the energy content established the use of bioelectrochemical systems is examined comparing real wastewater to the ‘model’ substrate of acetate. The abundance of exoelectrogenic bacteria within the sample, and the acclimation of these systems is examined through the use of most probable number experiments. It is found that there may be as few as 10-20 exoelectrogens per 100 mL. The impact of temperature, substrate and inoculum source on performance and community structure is analysed using pyrosequencing. Substrate is found to have a critical role, with greater diversity in acetate fed systems than the wastewater fed ones, indicating that something other than complexity is driving diversity. Laboratory scale microbial electrolysis cells are operated in batch mode fail when fed wastewater, whilst acetate fed reactors continue working, the reasons for this are examined. However a pilot scale, continuous flow microbial electrolysis cell is built and tested at a domestic wastewater treatment facility. Contrary to the laboratory reactors, this continues to operate after 3 months, and has achieved 70% electrical energy recovery, and an average 30% COD removal. This study concludes that wastewater is a very complex but valuable resource, and that the biological systems required to extract this resource are equally complex. Through the work conducted here a greater understanding and confidence in the ability of these systems to treat wastewater sustainably has been gained.EThOS - Electronic Theses Online ServiceEPSRCSchool of Chemical Engineering and Advanced MaterialsGBUnited Kingdo

Bioelectrochemical Systems for Energy Valorization of Waste Streams

Bioelectrochemical systems (BES) encompass a group of technologies derived from conventional electrochemical systems in which the electrodic reactions are directly or indirectly linked to the metabolic activity of certain types of microorganisms. Although BES have not yet made the leap to the commercial scale, these technologies hold a great potential, as they allow to valorize different liquid and gas waste streams. This chapter is devoted to exploring some of the possibilities that BES offer in the management and valorization of wastes. More specifically, it focuses on analyzing practical aspects of using BES for energy valorization of wastewaters and CO2-rich streams. Here, it is shown how BES can compete, in terms of energy usage, with conventional wastewater treatment technologies by exploiting the energy content of some of the chemicals present in the wastewater. Moreover, it explores how BES could enable using wastewater treatment plants as load regulation system for electrical grids. It also includes some insights on the capability of BES to recover valuable products such as fertilizers form wastes, a feature that allows this technology to promote energy efficiency in the fertilizers industry, and a sector that demands substantial amounts of energy in our world today. Finally, some of the most relevant scale-up experiences in the field are also covered