Overview
Our project has now achieved a complete proposed implementation. Sewage treatment plants are our target users. We install MFCs in wastewater treatment plants to harvest energy from organic matter in municipal wastewater and convert it into electricity for storage. The stored energy can be used in the daily use of the sewage treatment plant, thereby achieving energy conservation and emission reduction. More energy can also be further utilized by the power company. We respond to user needs and pay attention to the security problems in the application process and propose solutions. At the same time, we also took into account the shortcomings of the product and formulated a follow-up improvement plan.
Our product has the following advantages. First, users can reduce the cost of sludge incineration. Second, the electricity we generate can be stored for daily use, further reducing operating costs. Finally, the costs saved can be further invested in the research and development of technologies. We will also continuously improve our products to provide better solutions to the climate crisis from an energy perspective.
Target Users
The city we live in, Nanjing, China, is a super-large city with a population of over 9 million, which will inevitably produce a lot of life and industrial sewage. Our survey data shows that the total sewage volume in Nanjing reached 1,088.57 million tons a year, of which the total chemical oxygen demand (COD), an indicator to measure the content of organic matter in the water, was 63,100 tons. Therefore, urban sewage treatment plants can be our ideal target users and urban sewage can indeed be used as a direct source of electricity for our batteries.
Specific Process of Project Implementation
We use a special porous inorganic material to immobilize our strains. We will use specific plates to hold the material and wires to connect the plates to the outside world. When users use it, they only need to fix the electrode plate in the organic matter treatment tank and isolate oxygen, and it can be placed in multiple layers to increase the use area. According to the calculation of LOTUS, the annual loss rate will be less than 10%, and the plate can be replaced regularly. Using this method can save at least 5 million yuan in sludge treatment costs a year for a sewage treatment plant. The generated electricity is used for cascade utilization using retired power batteries, which further reduces the cost of power storage equipment. The large amount of electricity generated can be used for the daily operation of the sewage treatment plant, and the excess electricity can be further utilized by the regional power company.
Respond to User Needs
In the early design of the application scheme, we originally tried to immobilize the bacteria on a wyhole biofilm. However, after visiting the sewage treatment plant, we learned that the current sewage treatment method will produce a large amount of sludge. On the one hand, sludge has high water content, and incineration will consume a lot of energy. On the other hand, our biofilms will also be covered with sludge reducing their efficiency. Therefore, we contacted LOTUS to explore new application scenarios. This is our specific response to user needs.
Safety
For leakage prevention, we planned to design a completely sealed MFC unit because of the anaerobic environment required. The electrical pathway is the only connection between the whole system and the outside world. Therefore it can prevent the leakage of bacteria and silver ions. About Leakage Solution, for the elemental silver, we will use the standard metal leakage process. For the strains, on the one hand, a section of pipe containing an ultraviolet lamp could be designed downstream. On the other hand, filtering measures can be taken to reduce leakage. For ending plant solution, a conventional sterilisation procedure is applied directly to strains in the MFC containment vessel, e.g. UV irradiation or alcohol dunking. For elemental silver, we need to work only on the utilisation of the silver-containing wastewater. For more information please visit: Safety
Challenges
We still face many challenges that need to be solved gradually. First, how to build an oxygen-free environment in the organic matter treatment tank? If our unit provides an inlet and an outlet for the flow of sewage, how does the oxygen content of the water affect our efficiency? Second, can the modified strains adapt to the complex environment in sewage? Third, what is the power generation efficiency of using organic matter in sewage? Fourth, how should we choose the plate material so that it can be combined with our special material without compromising efficiency? Many problems are still waiting for us to solve, but we hope to push our project into reality with the greatest perseverance. In the process of product design, we have received affirmation and many suggestions from experts and practitioners, which is a great encouragement to us. Thanks to them here.
Wider Scenarios
In our interviews, many people have given us more inspiration, so that our MFC can be used in more scenarios. Professor Tian mentioned, if our MFCs can be used as a power source for artificial hearts under the premise of ensuring biosafety, it will be a boon for patients. Dr Song suggested small emergency storage batteries or medical devices such as pacemakers or detectors. Professor Li said if our battery could last for a month under the condition of controlled volume, it would be of great help to his research. Thanks to them for providing us with various ideas, in the follow-up work, we will consider more possibilities and better realize our value - improving human survival.