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Title: The effect of complex feed on bioelectrical systems (BESs) performance
Authors: Zhao, Fei
Issue Date: 2019
Publisher: Newcastle University
Abstract: Bioelectrochemical systems (BESs) are being widely proposed as an energy neutral or even positive alternatives to current aerobic wastewater treatment technologies. However, to achieve this goal their electrogenic performance will need to be substantially improved. In particular, the disparity of the performance of acetate-fed BESs and complex wastesfed BESs needs to be understood. In order to obtain rationale of the strategy of this improvement, this study sought to investigate the complex composition of wastewater in BESs by peeling off this effect into two major parts: the effect of the complex pathway in electron donor and the effect of the presence of alternative electron acceptor. In particular, glucose and sulphate was used as the model of complex electron donor and alternative electron acceptor respectively. In addition, this study investigated the effect of anode potential/carbon:sulphate (C:S) ratio on the major electrogenic pathways of these two components in BESs. This study found that the observed low current production and low coulombic efficiency of glucose-fed BESs was attributed to the low acetate availability (<6.24mM acetate) and the electron loss in the degradation pathway of glucose, formate and ethanol. In addition, the low abundance of the electrogenic microorganism Geobacteraceae was also associated with the low current production in the glucose-fed BESs. Increasing of anode potential improved the abundance of the electrogenic microorganism Geobacteraceae in the glucose-fed BESs but did not improve the acetate availability. The low current production in the BESs in the presence of sulphate was also attributed to the low abundance of the electrogenic microorganism Geobacteraceae. This was attributed to the toxicity of the by-products of sulphate presumably sulphide. The BESs reactors with a higher acetate concentration in their feed had a higher tolerance to this toxicity and were able to support a higher Geobacteraceae population. On the other hand, lower coulombic efficiency in the BESs in the presence of sulphate was largely attributed to the electron accumulation in the anodic sulphur deposit. Moreover, the negative impact of sulphate on the electrogenic performance in BESs was generally lower than the negative impact of complex organics such as glucose, sucrose and starch. Increasing anode potential increased the coulombic efficiency in the BESs in presence of sulphate in ii the short term, however this was caused by higher acetate consumption rather than lower sulphate reduction. In summary, this study provides detailed information of the effect of the complex components on the electrogenic performance of BESs and effect of anode potential/C:S ratio on the major electrogenic pathways of these complex components in BESs. This can be used to adjust anode potential in BESs to optimize the electrogenic performance based on the type of influent and to determine the role of BESs in wastewater treatment in terms of energy and valuable products recovery based on the upstream effluent.
Description: PhD Thesis
Appears in Collections:School of Engineering

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