School of Studies Process and Chemical Engineering (V)
Scientists at the Institute of Technical Microbiology are examining the wastewater of breweries and municipalities for substances that can be used to produce electricity or hydrogen.
The project focuses its work on analyzing wastewater for organic substances that serve as substrates for microorganisms. Brewery wastewater, wastewater from the cellulose filter industry and municipal wastewater are particularly suitable for treatment. The substances multiply in so-called microbial fuel cells (MFC) or microbial electrolysis cells (MEC).
Setting the flow of electricity in motion
To understand this process, it is helpful to imagine a battery. In it, current is generated by the electrochemical flow of electrons from the anode to the cathode. Similarly, in the early 20th century, it was first observed that some species of bacteria were capable of transferring electrons to an anode, this was later called a "microbial fuel cell." Since then, many basic mechanisms of electron transfer have been studied, but a deeper understanding of the processes is needed to optimize and commercialize these processes.
Every day, large amounts of wastewater are generated from industry as well as from private households. Proper treatment and purification is mandatory before returning the water to the environment. However, this process consumes a lot of energy and/or chemicals. For this reason, great efforts are being made worldwide to develop novel methods for environmentally friendly, resource-saving wastewater treatment. "A pioneering biological process is the microbial fuel cell, as organic carbon can be removed from wastewater and electrical power can be generated at the same time" says project supervisor Ahmed Elreedy.
The concept of this process is based on the ability of some microorganisms to transfer electrons directly or indirectly to external insoluble electron acceptors such as electrodes. Electrons, protons and CO2 are produced during the biological oxidation of organic matter in the anode. This process is the basis for energy conservation and growth of microorganisms. To generate a flow of electrons (electric current), the oxygen present in the cathode is reduced by the excess electrons. What remains is water. For example, treating one cubic meter of domestic wastewater can generate electricity of up to 1000 amperes.
Wastewater becomes clean
The fundamentals of electron transfer to an anode have only been partially studied and remain the subject of current research. "Our work, in addition to studying these electron transfer processes, is mainly focused on evaluating and optimizing process efficiency when dealing with real industrial wastewater," explains Ahmed Elreedy. "With this technology, we are not only able to purify water in a resource-saving way, but at the same time use this wastewater as a substrate for the sustainable generation of electric power," he said.
Ahmed Elreedy works as a research associate at the Institute of Technical Microbiology at Hamburg University of Technology. His research focuses on biological wastewater treatment with simultaneous energy generation using bioelectrochemical systems.
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