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Recovering valuable resources from wastewater will transform wastewater management from a treatment focused to sustainability focused strategy, and creates the need for new technology development. An innovative treatment concept - osmotic bioelectrochemical system (OsBES), which is based on cooperation between bioelectrochemical systems (BES) and forward osmosis (FO), has been introduced and studied in the past few years. An OsBES can accomplish simultaneous treatment of wastewater and recovery of resources such as nutrient, energy, and water (NEW). The cooperation can be accomplished in either an internal (osmotic microbial fuel cells, OsMFC) or external (microbial electrolysis cell-forward osmosis system, MEC-FO) configuration. In OsMFC, higher current generation than regular microbial fuel cell (MFC) was observed, resulting from the lower resistance of FO membrane. The electricity generation in OsMFC could greatly inhibit the reverse salt flux. Besides, ammonium removal was successfully demonstrated in OsMFC, making OsMFCs a promising technology for "NEW recovery" (NEW: nutrient, energy and water). For the external configuration of OsBES, an MEC-FO system was developed. The MEC produced an ammonium bicarbonate draw solute via recovering ammonia from synthetic organic solution, which was then applied in the FO for extracting water from the MEC anode effluent. The system has been advanced with treating landfill leachate. A mathematical model developed for ammonia removal/recovery in BES quantitatively confirmed that the NH4+ ions serve as effective proton shuttles across cation exchange membrane (CEM). / Ph. D.

Partial nitritation combined with the anaerobic ammonium oxidation (Anammox) process offers a way of replacing the conventional nitrogen removal process of nitrification-denitrification, lowering the need for oxygen and chemical input, as well as reducing the production of sludge. However, as a by-product of the biochemical reaction driven by anammox bacteria, it produces nitrate-nitrogen (NO3- - N) (16-26% nitrogen removed), which is problematic. Microbial desalination cells (MDCs) are a promising technology capable of converting biodegradable organics into electricity (by electroactive bacteria), providing for simultaneous desalination, and wastewater treatment. Despite being a promising technology, MDCs have limitations. The first-proof of-concept of MDC was demonstrated using acetate as the organic source, expensive platinum as a catalyst, and ferricyanide as an electron acceptor in the cathode that makes MDC costly, environmentally unfriendly, and unsustainable. This research investigated the integration of the anammox and nitration processes in MDCs as a long-term biocatalyst/biocathode for sustainable and energy-efficient nitrogen removal and electricity generation. A series of experiments were designed and performed to evaluate the performance of the anammox process as a biocatalyst in MDCs. The results concluded that the anammox process can be used as a biocatalyst to accept electrons in MDCs producing 444 mW/m3 of power density and 84% of ammonium nitrogen removal. Furthermore, the concept of using a one-stage nitritation anammox process as a biocathode in MDC was evaluated and produced a maximum power output of 1007 mW/m3. Two configurations of anammox MDCs (anaerobic-anammox cathode MDC (AnAmmoxMDC) and nitritation-anammox cathode MDC (NiAmoxMDC) were compared with an air cathode MDC (CMDC), operated in fed-batch mode. The NiAmoxMDC showed better performance in terms of power production and nitrogen removal. The co-existence of aerobic ammonium oxidizing bacteria (AOB) and anammox bacteria in the same biocathode of single-stage NiAmoxMDC concluded the resource-efficient wastewater treatment. Furthermore, two-stage nitritation anammox as a biocathode in MDC was evaluated and proved to be energy-efficient bioelectrochemical wastewater treatment by producing 1500 mW/m3 (300 mW/m2) of maximum power output. This research provides the first proof of concept that nitritation-anammox biocathode can provide a sustainable and energy-efficient nitrogen removal along with desalination and bioelectricity generation.

There is a growing awareness of the valuable nutrients (nitrogen and phosphorus) being lost in conventional wastewater treatment systems. Although the removal of these nutrients has been well addressed, efforts for nutrient recovery have seen little development. As the emphasis on sustainability in the wastewater treatment industry increases, conventional wastewater treatment processes are being re-evaluated and new treatment systems developed. A possible nutrient recovery mechanism is the precipitation of magnesium ammonium phosphate hexahydrate (MgNH4PO4·6H2O), commonly known as struvite. Human urine has been identified as a rich source of nutrients in wastewater; hence the separate collection of urine is considered a viable method of enabling struvite recovery. Since dilution of urine to a certain degree is inevitable, reconcentration of urine beyond the solubility limit of struvite is critical. Currently available methods for reconcentration (e.g., evaporation, freeze-thaw, reverse osmosis and electrodialysis) are relatively expensive with high energy demand. Thus, the research here aims to demonstrate nutrient reconcentration from diluted urine and simultaneous organic removal by using the principles of microbial desalination cells (MDCs), where energy released from organic oxidation is partially used for the separation of nutrient ions. With reduced energy demand, a sustainable method for the utilization of source-separated urine is examined. The performance of bioelectrochemical systems relies on the activity of exoelectrogenic bacteria to transfer electrons to the anode. An examination of exoelectrogen sensitivity at various wastewater treatment conditions (i.e. ammonia and oxygen) is an important component of this research. Methanogenesis is considered the greatest challenge in achieving practical applications in anaerobic bioelectrochemical systems. An electrolytic oxygen production method is suggested for effective control of methanogenesis in a feasible and cost-effective manner. / Thesis / Master of Applied Science (MASc)

Heavy metals are a growing environmental concern as they are unable to be metabolized in the environment, leading to bioaccumulation in the food chain and impacting human health. Treating heavy metals is difficult and expensive. Current methods include precipitation (which generates sludge that is costly to dispose of) or requires the use of a membrane, which fouls and requires regeneration. Microbial electrolysis cells (MECs) represent an alternative for treating heavy metal contaminated wastewater. Reactor components are cheap, and operation requires only a small amount of electricity. The electrically active biofilm oxidizes organics in the wastewater while transferring electrons first to the anode, then to the cathode, where aqueous metals are reduced to a solid deposit, a mechanism called electrodeposition. Few studies have been conducted to investigate the best operational conditions for heavy metal removal in MECs. In this study, the effects of hydrodynamics, applied voltage, and initial metal concentration on heavy metal removal mechanisms are investigated, and the best operational practices are determined on a high level. Mixing in the cathode chamber increased electrodeposition by 15%, decreased the cathode potential by -0.06 V, and increased current generation between 10-30%. Increasing the applied voltage from 0.6 V to 1.2 V increased electrodeposition by 22%. With both mixing and higher voltage applied, 93.35% of cadmium was removed from the catholyte in 24 hours. Although high voltage application maximized electrodeposition for short-term treatment, long-term treatment indicated lower applied voltage resulted in healthier MEC reactors, better overall metal recoveries, along with a more stable cathode potential. / Thesis / Master of Applied Science (MASc)

Effective wastewater treatment is needed to reduce the water pollution problem. However, massive energy is consumed in wastewater treatment, required to design an innovative system to reduce the energy consumption to solve the energy crisis. Integrated photobioelectrochemical system (IPB) is a powerful system to combine microbial fuel cells (MFCs) and algal bioreactor together. This system has good performance on the organic degradation, removal of nitrogen and phosphorus, and recover the bioenergy via electricity generation and algal harvesting. This dissertation is divided to twelve chapters, about various aspects of the working mechanisms and actual application of IPB. Chapter 1 generally introduces the working mechanisms of MFCs, algal bioreactor, and modeling. Chapter 2 demonstrates the improvement of cathode material to improve the structure and catalytic performance to improve the MFC performance. Chapter 3 describes the process to use microbial electrolysis cell (MEC) to generate biohythane for the energy recovery. Chapters 4 and 5 demonstrate the application of stable isotope probing to study Shewanella oneidensis MR-1 in the MFCs. Chapters 6 to 8 describe the application of models to optimize MFC and IPB system performance. Chapter 9 describes the strategy improvement for the algal harvesting in IPB. Chapter 10 describes the application of scale-up bioelectrochemical systems on the long-term wastewater treatment. Chapter 11 finally concludes the perspectives of IPBs in the wastewater treatment and energy recovery. This dissertation comprehensively introduces IPB systems in the energy recovery and sustainable wastewater treatment in the future. / Ph. D.

Bioelectrochemical systems couple the oxidation of an electron donor at the anode with the reduction of an electron acceptor at the cathode, using microorganisms to catalyse one or both reactions. When the overall reaction is exergonic, a power output is generated and the system is referred to as microbial fuel cell (MFC); when power is added to the system and hydrogen is produced at the cathode through electrolysis of water, the system is referred to as microbial electrolysis cell (MEC). This PhD thesis is principally focused on the microbial fuel cells technology. Microbial fuel cells are regarded as a sustainable technology for electric energy generation from the oxidation of organic substrates contained in wastewater. The rising need for renewable energy sources and sanitation has encouraged intense research in this novel technology. Nevertheless, up untill now the interest has been primarily focused on the anodic oxidation of organic matter contained in wastewater. However, in addition to organics, wastewater also contains other pollutants, such as soluble nitrogen compounds, for which specific treatment is required. In conventional wastewater treatment systems, the organics available in the wastewater are typically used as electron donor during denitrification. However, a considerable fraction (>50%) of the chemical oxygen demand (COD) is still oxidized aerobically due to the large recirculation flows from the nitrification to the denitrification stages required in anoxic/aerobic configurations to allow for low nitrate levels in the final effluent. This increased COD demand is normally fulfilled by supplementary COD addition, with consequent increase of treatment costs. Alternatively, microorganisms can use inorganic carbon substrates and inorganic electron donors such as hydrogen for denitrification. However, the use of compressed hydrogen is hampered by its low solubility. As a solution, electrochemical hydrogen production permits in situ delivery of the electron donor and is advantaged by simplified control and dissolution of H2. The energy requirements to provide reducing power for denitrification can be decreased if bacteria use the electrode directly as electron donor without intermediate hydrogen production in bioelectrochemical systems. However, fundamental knowledge on bioelectrochemical denitrification is still lacking, therefore, this PhD thesis aims to fill some of these knowledge gaps and to solve some of the bottlenecks of the use of biocathodes. In particular, the goals of this work are: (i) to produce a suitable microbial community able to use the cathode as the sole electron donor during denitrification; (ii) to engineer a bioelectrochemical system able to couple the cathodic denitrification with the oxidation of organics at the anode; (iii) to characterize and quantify the electron losses during anodic and cathodic processes; (iv) to develop a bioelectrochemical system that maximises the nitrogen removal by integrating the nitrification stage into the cathode; finally, (v) to provide an insight into the structural properties of the biofilm performing nitrogen removal at the cathode. The results reveal that microbes can effectively utilize the electrode as electron donor for nitrate reduction to gaseous nitrogen at a redox potential that excludes intermediate production of hydrogen. Measurements revealed that acetoclastic methanogenesis and bacterial growth were responsible for causing the major electron losses at the anode. Adjusting the anodic potential did not achieve a significant overall reduction of the electron losses. At the cathode, the charge transfer efficiencies were instead very high, with the losses only due to the generation of nitrous oxide. Moreover, adjustments of the cathode potential resulted in higher efficiency. High carbon and nitrogen removal was obtained with a COD demand for denitrification as low as 2.4 g per g nitrogen denitrified, which is much lower than typically observed in heterotrophic–based nitrogen removal technologies (>7 g g 1). Nitrogen was removed at rates up to 0.256 kg N m-3 d-1, which is comparable to other autotrophic denitrification processes. Simultaneous nitrification and denitrification was observed in a combined system with cathodic aeration, at bulk dissolved oxygen (DO) levels up to 5 mg L-1, which is considerably higher than normally considered feasible for the process. Confocal laser scanning microscope analysis revealed the existence of a structured biofilm where putative nitrifying organisms occupied the outer layers in contact with the aerated bulk liquid, and putative denitrifying organisms occupy the layers closer to the electrode. These findings are significant in the field of bioelectrochemical systems as they help to unravel some of the complex questions relating to biocathodes. Additionally, the system provides an attractive option to achieve a very high level of nitrogen removal from wastewater with low COD/N ratios due to the selective utilisation of the COD for the denitrification reaction via the electrical transfer of reducing equivalents from the anode to the cathode. However, this research creates new questions, particularly regarding the mechanisms of electron transfer at the cathode. Also a number of practical design and optimisation challenges need to be overcome before wider applications can be considered.

Sulfide is commonly present in domestic and industrial wastewater. As it is toxic, corrosive and odorous, it often needs to be removed prior to discharge to sewer or in the sewer system itself, and certainly before discharging into the environment. The scope of this thesis was to develop and demonstrate a novel, low energy electrochemical technique for the removal and recovery of sulfide from wastewater. In addition, this study aimed to evaluate the influence of inorganic sulfur species on organics oxidation in bioelectrochemical systems. The results demonstrate that sulfide oxidation to elemental sulfur can generate net electrical power in an electrochemical system. However, while the process effectively removed the sulfide from the wastewater, the elemental sulfur was deposited on the electrodes and deactivated them over time. Sulfide removal rate decreased from its initial value 80±2% to 62±4% after 8 days of operation when a lab scale reactor operated continuously in fuel cell mode (external resistance 10 Ω) with a loading rate of 0.43 ± 0.04 kg-S m-3 d-1 of total anodic compartment (TAC). The removal rate was constant for the following 50 days of operation and significantly decreased to about 10% after 90 days. On average, the power production was 5±1 W m-3 TAC with the coulombic efficiency of 88±5% but the maximum power production capacity of the reactor was 78 W m-3 TAC using potassium ferricyanide cathode. However, the deposited sulfur could be effectively removed and recovered as a concentrated sulfide/polysulfide solution by reversing the polarity of the electrode with low electrical energy input. The results also demonstrate that microbial consortia that developed due to the organic electron donors in the wastewater, negatively affected the performance of the sulfide removal process. The microorganisms were using the electrodeposited sulfur as a preferred electron acceptor over soluble sulfate and the electrode. This process was converting sulfur back to sulfide irrespective of the electrochemical conditions. In batch systems, the sulfide produced in this way could be re-oxidized at the anode and therefore the obtained coulombic efficiency was 97±2% for acetate oxidation. However, in continuous systems, depending on the operational conditions and wastewater characteristics, the sulfide could leave the system in the effluent. By applying cell polarity reversals at a sufficiently high frequency, it was possible to avoid biofilm formation and hence the re-generation of sulfide from the deposited sulfur. To confirm the effectiveness of the electrochemical sulfide removal in real wastewater, the process was demonstrated on the effluent of an anaerobic digester of a paper mill. Sulfide was removed from 44±7 to 8±2 mg-S L-1 at a removal rate of 0.845±0.133 kg-S m-3 TAC d-1 and a recovery rate of 75±4% with the voltage input of 0.52 to 1.3 V. Periodic switching in every 24 hours intervals between anode and cathode was an effective technique to maintain a good sulfide removal performance and avoid unwanted biofilm formation at the anode. Sulfide present in the wastewater could therefore be effectively removed from the liquid phase and harvested as elemental sulfur deposit on the electrode.

This thesis presents studies that examine microbial extracellular electron transfer that an emphasis characterizing how environmental conditions influence electron flux between microbes and a solid-phase electron donor or acceptor. I used bioelectrochemical systems (BESs), fluorescence and electron microscopy, chemical measurements, 16S rRNA analysis, and qRT-PCR to study these relationships among chemical, physical and biological parameters and processes. / Engineering and Applied Sciences