Understanding the Effects of Kinetic Limitations on Degradation Rates for Different Substrates in MFCs and the Impact on Trophic Layers on these Rates

全球对清洁能源和水的需求日益增长，引发了人们对微生物燃料电池（mfc）的兴趣。尽管在过去的25年里，这项技术取得了重大进展，但人们仍然缺乏对mfc内发生的过程的了解，例如复杂有机化合物的降解率。关于这些速率在现实条件下的有限文献阻碍了这项技术的优化。该研究项目的第一阶段旨在通过研究不同底物（醋酸盐、葡萄糖和淀粉）在动力学和非动力学有限系统以及不同温度下的降解率来帮助填补这一研究空白。先前的研究表明，与复杂的化合物（淀粉）相比，使用更简单的化合物（醋酸酯）的功率输出要高得多，因为醋酸酯不需要通过发酵来分解，这表明水解是这些系统中的限速步骤。然而，这是在充分搅拌的条件下进行的。实际上，许多mfc以批处理模式运行，而那些连续的mfc具有如此低的流量，以至于湍流不能产生充分搅拌的条件。如果要将mfc用于真正的废水处理，则需要充分了解其降解率和局限性。这样的速率需要对MFC反应器进行有效的建模和设计。为了确定系统是否受到动力学限制，将使用两种实验规模的反应堆配置；一种是充分搅拌，可以确定主要降解途径的基本限制；另一种是不搅拌的，这表明系统内的过程是发生在散装液体中还是发生在生物膜上。搅拌和非搅拌条件将用于确定mfc内的传质限制，并最终帮助设计反应器和操作条件，以最大限度地提高其处理复杂废物的效率。该研究项目的第二阶段将涉及重复这些初始实验，但采用更大的MFC配置来模拟分散的处理规模。这将允许在更现实的条件下进行测试。由于废水由高度多样化的底物组成，需要优化复杂化合物的分解。这个问题的一个潜在解决方案是在MFC系统中加入植物和基于土壤的培养基。植物MFC （p -MFC）是MFC的一种改进型材料，近年来在MFC性能方面取得了可喜的进展。研究表明，基于植物的mfc是成功的。然而，要提高这些系统在冬季的产量，还有很多工作要做。希望将土壤和植物引入MFC系统将在代谢食物网的营养水平上进一步受益。将植物连接到阴极的土壤将充满微生物，如蠕虫和许多不同的微生物群，所有这些都可能有助于这些系统内的消化/降解途径，并最终提高它们的性能和随后的废水处理和能量回收。一些研究已经证明了在家庭和大规模使用蠕虫处理和转化废水、污水和湿污泥的有效性。因此，本研究项目的最后阶段将调查营养层对l级mfc降解速率的影响。这些反应堆将设计和内置三套，并将在各种条件下进行初步测试。最初，测试将在实验室进行，最终将在室外进行测试，以使我们能够确定这项技术是否可行，是否可以应用于现实生活中。

Increasing global demand for clean energy and water has sparked recent interest in Microbial Fuel Cells (MFCs). Despite significant progress in improving this technology over the last 25 years, there remains a lack of understanding of the processes occurring within MFCs, such as degradation rates of complex organic compounds. Limited literature on what these rates are under realistic conditions hinders this technology's optimisation. This first phase of this research project aims to help fill this research gap by investigating the degradation rates of different substrates (acetate, glucose and starch) in kinetic and non-kinetic limited systems and at varying temperatures.Previous research has shown that power outputs when using simpler compounds (acetate) are significantly higher when compared to complex compounds (starch) due to acetate not needing to be broken down by fermentation, indicating hydrolysis is the rate-limiting step in these systems. However, this was under fully stirred conditions. In reality, many MFCs operate in batch mode, and those which are continuous, have such low flow rates that turbulence does not create fully stirred conditions. If MFCs are to be used for real wastewater treatment, the degradation rates and limitations need to be fully understood. Such rates are needed to model and engineer MFC reactors effectively.To determine whether the systems are kinetically limited, two bench-scale reactor configurations will be used; one that is fully stirred, allowing the basic limitations of the main degradation pathways to be determined; and one that is not stirred, giving an indication as to whether the processes within the system are taking place in the bulk liquid or on the biofilm. Stirring and non-stirring conditions will be used to determine the mass transfer limitations within the MFCs, and ultimately help design reactors and operational conditions which maximise their efficacy for treating complex wastes.The second phase of this research project will involve repeating these initial experiments but with larger MFC configurations that simulate decentralised treatment scales. This will allow for more realistic conditions to be tested. Since wastewater is comprised of highly multifarious substrates, the breakdown of complex compounds needs to be optimised. A potential solution to this is problem is the incorporation of plants as well as a soil based medium to the MFC system. Plant MFCs (P-MFCs), a modification of MFCs, have recently emerged and show promising results for MFC performance. Studies have demonstrated that plant based MFCs are successful. However, work still needs to be done to improve the output of these systems in winter months. It is the hope that the introduction of soil and plants to an MFC system will give the further benefit of trophic levels within the metabolic food web. The soil connecting the plants to the cathode will be full of organisms such as worms and many different microbiota, all of which could possibly aid the digestion/degradation pathways within these systems and ultimately increase their performance and subsequent wastewater treatment and energy recovery. Several studies have demonstrated the effectiveness of using worms to treat and transform wastewater, sewage, and wet sludge at both household and large-scale.The final phase of this research project will therefore investigate the impact of trophic layers on the rates of degradation in L-scale MFCs. The reactors will be designed and built-in triplicate and will undergo preliminary tests under variable conditions. Initially, tests will be carried out in the laboratory, and eventually will be tested outside to enable us to determine if this technology is viable and if it can be implemented into real life set ups.