Yes / In this paper, a one-dimensional mathematical model based on coupled differential and algebraic equations has been developed for analysing the separation mechanism of a N-nitrosamine in a spiral-wound reverse osmosis process. The model is based on Spiegler and Kedem’s work on mass transport and Darcy’s law and concentration polarization to analyse the pressure drop and mass transfer coefficient in the module feed channel respectively. The model is built using the gPROMS software suite and validated using N-nitrosamine rejection experimental data from the literature, obtained by using a pilot-scale cross-flow reverse osmosis filtration system. Analysis results derived from the model corroborate experimental data.

Yes / Reverse Osmosis (RO) has already proved its worth as an efficient treatment method in chemical and environmental engineering applications. Various successful RO attempts for the rejection of organic and highly toxic pollutants from wastewater can be found in the literature over the last decade. Dimethylphenol is classified as a high-toxic organic compound found ubiquitously in wastewater. It poses a real threat to humans and the environment even at low concentration. In this paper, a model based framework was developed for the simulation and optimisation of RO process for the removal of dimethylphenol from wastewater. We incorporated our earlier developed and validated process model into the Species Conserving Genetic Algorithm (SCGA) based optimisation framework to optimise the design and operational parameters of the process. To provide a deeper insight of the process to the readers, the influences of membrane design parameters on dimethylphenol rejection, water recovery rate and the level of specific energy consumption of the process for two different sets of operating conditions are presented first which were achieved via simulation. The membrane parameters taken into consideration include membrane length, width and feed channel height. Finally, a multi-objective function is presented to optimise the membrane design parameters, dimethylphenol rejection and required energy consumption. Simulation results affirmed insignificant and significant impacts of membrane length and width on dimethylphenol rejection and specific energy consumption, respectively. However, these performance indicators are negatively influenced due to increasing the feed channel height. On the other hand, optimisation results generated an optimum removal of dimethylphenol at reduced specific energy consumption for a wide sets of inlet conditions. More importantly, the dimethylphenol rejection increased by around 2.51% to 98.72% compared to ordinary RO module measurements with a saving of around 20.6% of specific energy consumption.

Yes / Reverse osmosis system has been widely used for the separation of organic and non-organic pollutants present in wastewater. The main aim of this study is to develop a one dimensional steady state model based on the three-parameter Spiegler-Kedem methodology using the gPROMS software and validate it by assessing the performance of membrane rejection for the separation data of aqueous solutions of phenol under different concentrations and pressures. Considerations of the variance of pressure, flow rate, solute concentration, solvent and solute fluxes and mass transfer coefficient along the feed channel were included in the model. Furthermore, an optimization methodology for the gEST parameter estimation tool has been developed in the gPROMS and used with experimental data in order to estimate the best values of the separation membrane parameters and the friction parameter. The simulation results of this model have been corroborated by experimental data.

Yes / Reverse osmosis (RO) has found extensive applications in industry as an efficient separation process in comparison with thermal process. In this study, a one-dimensional distributed model based on a wastewater treatment spiral-wound RO system is developed to simulate the transport phenomena of solute and water through the membrane and describe the variation of operating parameters along the x-axis of membrane. The distributed model is tested against experimental data available in the literature derived from a chlorophenol rejection system implemented on a pilot-scale cross-flow RO filtration system with an individual spiral-wound membrane at different operating conditions. The proposed model is then used to carry out an optimisation study using a genetic algorithm (GA). The GA is developed to solve a formulated optimisation problem involving two objective functions of RO wastewater system performance. The model code is written in MATLAB, and the optimisation problem is solved using an optimisation platform written in C++. The objective function is to maximize the solute rejection at different cases of feed concentration and minimize the operating pressure to improve economic aspects. The operating feed flow rate, pressure and temperature are considered as decision variables. The optimisation problem is subjected to a number of upper and lower limits of decision variables, as recommended by the module’s manufacturer, and the constraint of the pressure loss along the membrane length to be within the allowable value. The algorithm developed has yielded a low optimisation execution time and resulted in improved unit performance based on a set of optimal operating conditions.

Yes / Reverse osmosis (RO) has long been recognised as an efficient separation method for treating and removing harmful pollutants, such as dimethylphenol in wastewater treatment. This research aims to study the effects of RO network configuration of three modules of a wastewater treatment system using a spiral-wound RO membrane for the removal of dimethylphenol from its aqueous solution at different feed concentrations. The methodologies used for this research are based on simulation and optimisation studies carried out using a new simplified model. This takes into account the solution-diffusion model and film theory to express the transport phenomena of both solvent and solute through the membrane and estimate the concentration polarization impact respectively. This model is validated by direct comparison with experimental data derived from the literature and which includes dimethylphenol rejection method performed on a small-scale commercial single spiral-wound RO membrane system at different operating conditions. The new model is finally implemented to identify the optimal module configuration and operating conditions that achieve higher rejection after testing the impact of RO configuration. The optimisation model has been formulated to maximize the rejection parameters under optimal operating conditions of inlet feed flow rate, pressure and temperature for a given set of inlet feed concentration. Also, the optimisation model has been subjected to a number of upper and lower limits of decision variables, which include the inlet pressure, flow rate and temperature. In addition, the model takes into account the pressure loss constraint along the membrane length commensurate with the manufacturer’s specifications. The research clearly shows that the parallel configuration yields optimal dimethylphenol rejection with lower pressure loss.

Yes / Reverse Osmosis (RO) can be considered as one of the most widely used technologies used to abate the existence of highly toxic compounds from wastewater. In this paper, a multilayer artificial neural network (MLANN) with Genetic Algorithm (GA) have been considered to build a comprehensive mathematical model, which can be used to predict the performance of an individual RO process in term of chlorophenol removal from wastewater. The MLANN model has been validated against 70 observational experimental datasets collected from the open literature. The MLANN model predictions have outperformed the predictions of several structures developed for the same chlorophenol removal using RO process based on performance in terms of coefficient of correlation, coefficient determination (R2) and average error (AVE). In this respect, two structures (4-2-2-1) and (4-8-8-1) were also used to study the effect of a number of neurons in the hidden layers based on the difference between the measured and ANN predicted values. The model responses clearly confirm the successfulness of estimating the chlorophenol rejection for network structure 4-8-8-1 based on a wide range of the control variables. This also represents a high consistency between the ANN model predictions and the experimental data.

The treatment of water and wastewater is energy intensive, and there is an urgent need to develop new approaches to address the water-energy challenges. Bioelectrochemical systems (BES) are energy-efficient technologies that can treat wastewater and simultaneously achieve multiple functions such as energy generation, hydrogen production and/or desalination. The objectives of this dissertation are to understand the fundamental microbiology of BES, develop cost-effective cathode catalysts, optimize the process engineering and identify the application niches. It has been shown in Chapter 2 that electrochemically active bacteria can take advantage of shuttle-mediated EET and create optimal anode salinities for their dominance. A novel statistical model has been developed based on the taxonomic data to understand and predict functional dynamics and current production. In Chapter 3, 4 and 5, three cathode catalyst (i.e., N- and S- co-doped porous carbon nanosheets, N-doped bamboo-like CNTs and MoS2 coated on CNTs) have been synthesized and showed effective catalysis of oxygen reduction reaction or hydrogen evolution reaction in BES. Chapter 6, 7 and 8 have demonstrated how BES can be combined with forward osmosis to enhance desalination or achieve self-powered hydrogen production. Mathematical models have been developed to predict the performance of the integrated systems. In Chapter 9, BES have been used as a research platform to understand the fate and removal of antibiotic resistant genes under anaerobic conditions. The studies in this dissertation have collectively demonstrated that BES may hold great promise for energy-efficient water and wastewater treatment. / Ph. D. / Water and energy are prerequisites to life. Every day, a lot of energy and money are spent on treating wastewater and producing fresh water. Bioelectrochemical systems (BES) are new technologies that can treat water and wastewater with low energy consumption. BES typically consist of an anode (where microorganisms break down organic matter) and a cathode, and work like a battery. Currently, BES are only studied in laboratories and not applied in real-world situations, because the performance needs to be improved and fundamentals remain to be better understood. The studies in this dissertation aim to address these problems and make BES toward practice. It has been shown in Chapter 2 that, under high salinity, some bacteria grow faster in the anode and the BES can produce higher electricity. It is difficult to understand the roles of every bacterium with current molecular techniques, and thus statistical methods are applied to estimate their possible functions. In Chapter 3, 4 and 5, three materials have been fabricated and functioned as the catalysts for electricity generation. Chapter 6, 7 and 8 have demonstrated how BES can be combined with forward osmosis, a spontaneous water diffusion process, to enhance desalination or achieve self-powered hydrogen production. Mathematical equations have been combined to simulate the process of biological metabolisms, water diffusion and ion migration. In Chapter 9, BES have been shown to remove antibiotic resistant gene, an emerging contaminant caused by the excessive use of antibiotics. The studies in this dissertation have collectively demonstrated that BES may be the answer to future water and wastewater treatment.

京都大学 / 新制・課程博士 / 博士(地球環境学) / 甲第25467号 / 地環博第253号 / 新制||地環||51(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)准教授 田中 周平, 教授 越後 信哉, 教授 梶井 克純 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

Current treatment of wastewater can effectively remove the contaminants; however, the effluent is still not widely reused because of some undesired substances like pathogens and trace organic chemicals. To promote water reuse, membrane-based technologies have emerged as a robust and more efficient alternative to current treatment practice. Among these membrane processes, forward osmosis (FO) utilizes an osmotic pressure gradient across a semi-permeable membrane to reclaim high-quality water. Still, several key challenges remain to be addressed towards broader FO application, including energy-intensive draw regeneration to yield product water and salinity buildup in the feed solution. To bypass energy-intensive draw regeneration, commercial solid fertilizers was utilized as a regeneration-free draw solute (DS), harvesting fresh water towards direct agricultural irrigation. However, using nutrient-rich fertilizers as DS resulted in an elevated reverse solute flux (RSF). This RSF, known as the cross-membrane diffusion of DS to the feed solution, led to deteriorated solute buildup on the feed side, reduced osmotic driving force, increased fouling propensity, and higher operation cost. To effectively mitigate solute buildup while achieving energy-efficient water reclamation, a parallel electrodialysis (ED) device was integrated to FO for DS recovery in the feed solution. The salinity in the feed solution was consistently controlled below 1 mS cm-1 via the hybrid FO-ED system. Considering solute buildup is merely a consequence of RSF, direct control of RSF was further investigated via operational strategy (i.e., an electrolysis-assisted FO) and membrane modification (i.e., surface coating of zwitterion-functionalized carbon nanotubes). Significantly reduced RSF (> 50% reduction) was obtained in both approaches with minor energy/material investment. With two major bottlenecks being properly addressed for energy-efficient water reclamation, FO was further integrated with a microbial electrolysis cell (MEC) to achieve integrated nutrient-energy-water recovery from high-strength wastewater (i.e., the digestor centrate). The abovementioned research projects are among the earliest efforts to address multiple key challenges of FO during practical application, serving as a cornerstone to facilitate the transformation of current water/wastewater treatment plant to resource recovery hub in order to ensure global food-energy-water security. / Doctor of Philosophy / Exploring alternative water supply, for instance via reusing wastewater, will be essential to deal with the global water crisis. Current wastewater treatment can effectively remove the contaminants; however, the treated wastewater is still not widely reused due to the possible presence of residual contaminants. In recent years, membrane-based technologies have emerged as a promising treatment process to produce clean water. Among all available membrane technologies, forward osmosis (FO) takes advantage of the osmotic pressure difference across a special membrane to extract fresh water from a low-salinity FEED solution (for example, wastewater) to a high-salinity DRAW solution. The reclaimed fresh water can be reused for other applications. Still, the FO process is facing several critical challenges for broader applications. The first challenge is that additional energy is required to separate clean water from the diluted DRAW solution, leading to notably increased energy consumption for the FO process. To bypass this energy-intensive separation, commercial solid fertilizers was utilized as a separation-free DRAW solution for FO process. Once the clean water is extracted to the DRAW solution (fertilizer), the diluted fertilizer solution together with the fresh water can be directly used for agricultural irrigation. The second challenge is that, when fertilizer is applied as the DRAW solution, nutrient rich fertilizers can penetrate the FO membrane and escape to the FEED solution (wastewater). This phenomenon is known as the reverse solute flux (RSF). RSF can result in many adverse effects, such as wastewater contamination and increased operational cost. To prevent this, we used an additional device named electrodialysis to effectively recapture the “escaped” fertilizers in the FEED solution. Besides this indirect approach to recover escaped fertilizers, we also investigated direct approaches to control RSF, including operational strategy and membrane modification. With two major challenges being properly addressed for energy-efficient water reclamation, FO was further combined with a microbial electrolysis cell (MEC) to achieve multiple resource recovery from wastewater, including water, nutrient, and energy components. The above mentioned research projects are among the earliest efforts to address multiple key challenges of FO during water and resource recovery from wastewater to ensure global food-energy-water security.

Many industrial processes would require enormous amounts of water, which could ultimately result in wastewater. Water scarcity in many parts of the world makes this situation unsustainable. In order to reuse wastewater in industrial processes or for other purposes, wastewater must be treated properly. In industrial wastewater treatment, electrocoagulation-flotation (ECF) can be used to dissolve sacrificial electrodes and produce metal coagulant in-situ by applying a current to the electrodes. The reactor design and electrode configuration can profoundly affect the performance of electrocoagulation-flotation (ECF). While most conventional ECF reactors use an open-vertical electrode configuration in rectangular cells, mixing is limited by vertical electrodes that make a barrier and disrupt the flow hydrodynamics. The effects of these factors may influence removal efficiency, flow hydrodynamic, floc formation, and flotation/settling characteristics. The present work aimed to optimize the ECF process by developing an innovative electrode configuration. A variety of parameters were examined to determine the effectiveness of the removal of contaminants from industrial wastewater that had turbidity, emulsified oil, and heavy metals (Si, Zn, Pb, Ni, Cu, Cr, and Cd), as well as stirring speed and foaming. Additionally, the experimental results of the innovative electrode configuration were compared with those of the conventional rectangular cell with plate electrode configuration. Based on the results, the innovative electrode configuration consumed approximately 20% less energy than a conventional ECF for operating times of 10, 20, 30, 32, 48, and 70 minutes. As a result of the enhanced flow hydrodynamic, the formed gas bubbles tilted toward the center, significantly reducing foam formation. There was also an investigation of the dominant operating parameters for electrocoagulation-flotation (ECF) that could affect the removal efficiency, including current density (CD), initial pH, electrolytic conductivity, dosage of coagulant, operating time, initial turbidity concentration, and stirring speed. In addition, a novel approach has been proposed for evaluating EC performance and selecting an appropriate process for removing sludge based on the intake's initial concentration. Keywords: Electrode configuration, electrocoagulation process, electro-flotation, energy consumption, removal efficiency, Electrochemical treatment, Aluminium electrode, Turbidity removal, TOC removal, operating parameters, computational fluid dynamics, Reynolds number, mass transfer, pH evolution.:Table of Contents Abstract 7 1. Introduction 16 1.1. The electrocoagulation process 17 1.2. Problem statement 19 1.3. Objectives 20 1.4. Scope of the work 21 2. Literature survey 23 2.1. Industrial wastewater and treatment methods 24 2.1.1. Impact of industrial growth 24 2.1.2. An analysis of global industrial growth based on statistics 25 2.1.3. Extensive sources of industrial effluent 26 2.1.4. Wastewater and reserve rehabilitation in industry 34 2.1.5. Applied techniques in industrial wastewater treatment 40 2.2. Electrocoagulation (ECF) 50 2.3. Comparison of EC with other treatment methods 50 2.4. Basic concepts and theory of coagulation and electrocoagulation 53 2.5. Electrocoagulation applications 58 2.5.4. Textile industry 60 2.5.5. Leather Tanning Industry 61 2.5.6. Metal-bearing industrial effluents 61 2.5.7. Pulp and paper industry 62 2.5.8. Petroleum refinery 63 2.6. Type and Configuration of the Electrodes 64 2.6.1. Case of Al electrodes 66 2.6.2. Case of Fe electrodes 68 2.7. Reactor design 71 2.6. Modeling 72 2.6.1. Kinetics 73 2.7. Impact of electrocoagulation operating condition on contaminant removal efficiency 75 2.7.1. Effect of current density 75 2.7.2. Effect of initial pH 75 2.7.3. Effect of operating time 76 2.7.4. Effect of electro conductivity 76 2.7.5. Effect of stirring speed 77 2.7.6. Effect of concentration 77 2.7.7. Effect of gap between the electrodes 77 2.7.8. Effect of temperature 78 2.8. Economical aspects and cost analysis 78 3. Material and methods of the tests 80 3.1. Test procedure 1: Impact of operating parameters on removal of turbidity 81 3.1.1. Operating conditions 81 3.1.2. EC cell construction and electrode arrangement 82 3.1.3. Synthetic wastewater 85 3.1.4. Analytical methods and EC procedure 86 3.1.5. Anodic and cathodic reactions 87 3.1.6. Electrical double layer and particle stability 89 3.2. Test procedure 2: Spiral electrode configuration 91 3.2.1. Experimental Setup 91 3.2.2. Sampling and analytical measurements 95 3.2.3. Experimental procedure 95 4. Results and discussion 97 4.1. Test procedure 1: Impact of operating parameters on removal of turbidity 98 4.1.1. Effect of current density (CD) 98 4.1.2. Effect of initial pH 100 4.1.3. Effect of electrolytic conductivity 104 4.1.4. Effect of coagulant dosage, electrode and energy consumption 106 4.1.5. Effect of current density and operating time on initial turbidity concentration 107 4.1.6. Effect of stirring speed 111 4.1.7. Effect of electrode passivation 112 4.2. Test procedure 2: Spiral electrode configuration 115 4.2.1. Removal efficiency of contaminants 115 4.2.2. Effect of stirring speed and ECF configuration on removal efficiency 119 4.2.3. Energy consumption and voltage rise 123 4.2.4. Foaming effect 126 4.3. Computational Fluid Dynamics (CFD) Simulation 128 5. Conclusions and future work 138 5.1. Conclusions 139 5.2. Future works 142 References 143 6. Appendix 159