Browsing by Author "Jain, Akshay"

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    Cathode-enhanced wastewater treatment in bioelectrochemical systems
    Jain, Akshay; He, Zhen (Nature Research, 2018-12-05)
    Bioelectrochemical systems (BES) have been intensively studied as a new technology for wastewater treatment. However, the treatment efficiency of BES anodes is limited and the anode effluent usually cannot be directly discharged or reused. To enhance the treatment, BES cathodes may be used for additional treatment of selected contaminants. This has been investigated in a number of approaches, which can be grouped into cathode-stimulated treatment and cathode-supported treatment. The former involves electron transfer directly to reduce contaminants like nitrate or dye compounds, while the latter can accomplish contaminant removal by aerobic oxidation, algal growth, production of strong oxidants for advanced oxidation, and/or membrane treatment. This paper aims to provide a concise view and discussion on the cathode-promoted wastewater treatment in BES, analyze challenges pertaining to the cathode treatment, and offer suggestions on the future development of BES for maximized treatment performance.
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    Feasibility of using Waste Heat as a power source to operate Microbial Electrolysis Cells towards Resource Recovery
    Jain, Akshay (Virginia Tech, 2020-05-05)
    Wastewater treatment has developed as a mature technology over time. However, conventional wastewater treatment is a very energy-intensive process. Bioelectrochemical system (BES) is an emerging technology that can treat wastewater and also recover resources such as energy in the form of electricity/hydrogen gas and nutrients such as nitrogen and phosphorus compounds. Microbial electrolysis cell (MEC) is a type of BES that, in the presence of an additional voltage, can treat wastewater and generate hydrogen gas. This is a promising approach for wastewater treatment and value-added product generation, though it may not be sustainable in the long run, as it relies on fossil fuels to provide that additional energy. Thus, it is important to explore alternative renewable resources that can provide energy to power MEC. Waste heat is one such resource that has not been researched extensively, particularly at the low-temperature spectrum. This was utilized as a renewable resource by converting waste heat to electricity using a device called thermoelectric generator (TEG). TEG converted simulated waste heat from an anaerobic digester to power an MEC. The feasibility of TEG to act as a power source for an MEC was investigated and its performance compared to the external power source. Various cold sources were analyzed to characterize TEG performance. To explore this integrated TEG-MEC system further, a hydraulic connection was added between the two systems. Wastewater was used as a cold source for TEG and it was recirculated to the anode of the MEC. This system showed improved performance with both systems mutually benefitting each other. The operational parameters were analyzed for the optimization of the system. The integrated system could generate hydrogen at a rate of 0.36 ± 0.05 m3 m-3 d-1 for synthetic domestic wastewater treatment. For the practical application, it is necessary to estimate the cost and narrow the focus on the functions of the system. Techno-economic analysis was performed for MEC with cost estimation and net present value model to understand the economic viability of the technology. The application niche of the BES was described and directions for addressing the challenges towards a full-scale operation were discussed. The present system provides a sustainable method for wastewater treatment and resource recovery which can play an important role in human health, social and economic development and a strong ecosystem.