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Thesis defences

PhD Oral Exam - Soodeh Abedini, Civil Engineering

Development of an electrochemical device for converting greenhouse gases to fuel and add-value products in wastewater treatment plants


Date & time
Monday, December 20, 2021 (all day)
Cost

This event is free

Organization

School of Graduate Studies

Contact

Daniela Ferrer

Where

Online

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

The rapid increase of greenhouse gases (GHG) in the atmosphere generates several consequences; one of them is global warming. One of the most obvious effects of global warming is the increase in temperatures around the world and changes in climate. Several sources which produce carbon dioxide, methane and nitrous oxide at a high level are recognized. Some of these sources are transportation, industrial sources, chemical production, petroleum production, agriculture, and wastewater treatment plants (WWTPs). WWTPs are recognized as one of the more extensive sources of GHG emissions such as CO2, CH4, and N2O. Due to biological microbial anaerobic and aerobic respiration processes.

Thus, conversion of CO2, CH4, and N2O generated in the WWTPs into add-value products without the utilization of fossil fuels is so important to control of the global warming.

The main objective of this study is production of add-value products from biogas and simultaneously mitigating the emission of GHG. For this reason, a novel electrochemical device has been proposed to convert of biogas to the fuel and simultaneously produce the valuable by-products (such as struvite, fungicide) and remove impurities from effluent served as an electrolyte. The investigations were conducted at lab and in a wastewater treatment plant in three phases and several stages. In phase 1, a novel electrochemical device was designed based on sustainable development principals. Phase 2 focused on generation the optimal operation conditions for electrochemical device to be able to convert CO2, CH4, the mixture of CO2 and CH4 into fuel and valuable by-products. The influence of gas input time, gas flowrate, the configuration of the electrochemical device, temperature and electrical potential on by-product production were investigated. The removal of N2O and its impact on the properties (the WWTP effluent used as an electrolyte) were also studied.

In the phase 3 the possibility of using real effluent as an electrolyte was investigated at WWTP. The study focused on conversion of biogas to the fuel and production of some by-products such as struvite from contaminated effluent.
The results showed that methanol is the main product of interest. Its production from pure biogas reached 83.95 ppm, while from real biogas 2.5 times less at lower temperature. Besides the device was able to produce copper (II) hydroxide and copper (II) sulphate, respectively, in ambient temperature using only 8V/cm.

The study described the impact of gas input duration, its flowrate, temperature fluctuation, electrical potential, and device configuration on methanol production.

Application of on-site WWTP effluent as an electrolyte, permitted to remove efficiently nitrate (87.86%), phosphate (98%), and sulphate (79.01%). Hence, this system beside depletion of GHG, production of methanol, struvite and fungicide can improve the quality of effluent and better protect water resources. Furthermore considering circular economy, produced methanol at WWTP on-site, can be return to the influent as an extra carbon source for nitrification process and decrease N2O generation.

Finally, a model was developed to investigate the effect of operational parameters on the methanol production efficiency. For this purpose, the Modelica V.17 based EMTtype simulation tool has been used.

The model demonstrates how different gas input durations, and the faradaic efficiencies of different products influence the methanol production. The results obtained through experimental study and modeling show good consistency.

This research results show the capability of the proposed device to convert biogas to methanol based on sustainable development principles. The electrochemical device can be introduced to a municipal wastewater treatment plant in order to mitigate greenhouse gases and reusing effluent as an electrolyte, but also it can be used in many industrial sectors.

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