Experimental Characterization of Membrane Fouling under Intermittent Operation and Its Application to the Optimization of Solar Photovoltaic Powered Reverse Osmosis Drinking Water Treatment Systems

This thesis presents a novel experimental characterization of reverse osmosis membrane fouling from the intermittent operation of solar powered water treatment systems. This thesis also depicts the development of an analytical membrane fouling model and a design framework to configure location-customized solar photovoltaic reverse osmosis systems. The World Health Organization estimates that 760 million people worldwide lack access to clean drinking water. The regions with the highest water scarcity are usually off-grid, remote and have high solar insolation. Therefore, the use of solar powered reverse osmosis water treatment systems is a viable solution. However, to minimize the costs, these systems are configured with minimal battery storage and operated intermittently with extended shutdown periods. Literature lacks an experimental characterization of the effect of this intermittent operation on membrane fouling and an associated design optimization framework. This research work on reverse osmosis water treatment systems is divided into two main parts: (1) the experimental characterization of membrane fouling under intermittent operation, and (2) the development of an analytical membrane fouling model and a design optimization framework for these systems. A new fully-instrumented experimental lab-scale system was designed, built, commissioned and operated with triplicate measurements of membrane permeability and membrane salt rejection for the experimental characterization. A new pilot-scale experimental system was also designed, built and operated. The membrane fouling was characterized experimentally for intermittent and continuous operation. The effect of anti-scalant and rinsing was also investigated. Two types of experimental water was tested: an experimental MilliQ-based matrix and an experimental groundwater-based matrix. The groundwater was from Nobleton, Ontario. In addition, membrane autopsy was performed using scanning electron microscopy. An analytical membrane fouling model was developed based on the experimental results. Furthermore, a novel design framework was developed using this new analytical membrane fouling model. This design optimization framework can be used for the configuration of community-specific solar photovoltaic reverse osmosis systems that are reliable throughout the system life at a minimal cost. The design optimization framework can be adapted for other modular systems such as renewable power systems for off-grid communities, remote First Nations, Métis, and Inuit communities, or remote mining sites.Ph.D.2019-07-10 00:00:0

The Pore Structure of Indiana Limestone and Pink Dolomite for the Modeling of Carbon Dioxide in Geologic Carbonate Rock Formations

The primary objective was to predict the relative storage capacity of carbonate rocks relevant for carbon dioxide sequestration. To achieve this, a detailed pore scale characterization of model carbonate rocks, Indiana Limestone and Pink Dolomite, was conducted utilizing micro-computed tomography (microCT) data using pore network modeling and invasion percolation simulations. For the first time in literature, Pink Dolomite’s pore space characteristics were analyzed. A secondary objective was to compare thresholding techniques as applied to carbonates which exhibit dual porosity (porosity at multiple length scales). The analysis showed the sensitivity of existing methods to the thresholding technique, imaging method and material. Overall, the contributions of this work provide an assessment of two carbonates relevant for carbon capture and storage at the pore scale; and a preliminary assessment into thresholding dual porosity carbonates.MAS

Pore Structure Characterization of Indiana Limestone and Pink Dolomite from Pore Network Reconstructions

International audienceCarbon sequestration in deep underground saline aquifers holds significant promise for reducing atmospheric carbon dioxide emissions (CO2). However, challenges remain in predicting the long term migration of injected CO2. Addressing these challenges requires an understanding of pore-scale transport of CO2 within existing brine-filled geological reservoirs. Studies on the transport of fluids through geological porous media have predominantly focused on oil-bearing formations such as sandstone. However, few studies have considered pore-scale transport within limestone and other carbonate formations, which are found in potential storage sites. In this work, high-resolution micro-Computed Tomography (microCT) was used to obtain pore-scale structural information of two model carbonates: Indiana Limestone and Pink Dolomite. A modified watershed algorithm was applied to extract pore network from the reconstructed microCT volumetric images of rock samples and compile a list of pore-scale characteristics from the extracted networks. These include statistical distributions of pore size and radius, pore-pore separation, throat radius, and network coordination. Finally, invasion percolation algorithms were applied to determine saturation-pressure curves for the rock samples. The statistical distributions were comparable to literature values for the Indiana Limestone. This served as validation for the network extraction approach for Pink Dolomite, which has not been considered previously. Based on the connectivity and the pore-pore separation, formations such as Pink Dolomite may present suitable storage sites for carbon storage. The pore structural distributions and saturation curves obtained in this study can be used to inform core- and reservoir-scale modeling and experimental studies of sequestration feasibility

Pore Structure Characterization of Indiana Limestone and Pink Dolomite from Pore Network Reconstructions

Carbon sequestration in deep underground saline aquifers holds significant promise for reducing atmospheric carbon dioxide emissions (CO2). However, challenges remain in predicting the long term migration of injected CO2. Addressing these challenges requires an understanding of pore-scale transport of CO2 within existing brine-filled geological reservoirs. Studies on the transport of fluids through geological porous media have predominantly focused on oil-bearing formations such as sandstone. However, few studies have considered pore-scale transport within limestone and other carbonate formations, which are found in potential storage sites. In this work, high-resolution micro-Computed Tomography (microCT) was used to obtain pore-scale structural information of two model carbonates: Indiana Limestone and Pink Dolomite. A modified watershed algorithm was applied to extract pore network from the reconstructed microCT volumetric images of rock samples and compile a list of pore-scale characteristics from the extracted networks. These include statistical distributions of pore size and radius, pore-pore separation, throat radius, and network coordination. Finally, invasion percolation algorithms were applied to determine saturation-pressure curves for the rock samples. The statistical distributions were comparable to literature values for the Indiana Limestone. This served as validation for the network extraction approach for Pink Dolomite, which has not been considered previously. Based on the connectivity and the pore-pore separation, formations such as Pink Dolomite may present suitable storage sites for carbon storage. The pore structural distributions and saturation curves obtained in this study can be used to inform core- and reservoir-scale modeling and experimental studies of sequestration feasibility

Effects of Substituting Activated Carbon with Titanium-Dioxide-Coated Cenospheres in Conventional Aquarium Filters

We investigated the effectiveness of TiO2 cenospheres in reducing the concentrations of three common harmful compounds, ammonium, nitrate, and nitrite, in fish aquariums. These cenospheres can contribute to more sustainable and eco-friendly aquarium filtration systems while also improving the health of fish. We designed a 30-day experiment with three treatment groups based on the filter type: (1) a control group with a conventional aquarium filter, (2) a group with a TiO2 cenosphere filter, and (3) a group with a dark TiO2 cenosphere filter. The water quality was the same baseline in all groups, and each tank was monitored daily for changes in temperature, pH, ammonia, nitrate, and nitrite concentrations. We found that the TiO2 cenosphere filter was effective in reducing the concentrations of all three pollutants. By the end of the experimental period, the average concentration of nitrite in the control group was 10.7 µM, while the average concentration in the TiO2 cenosphere filter group dropped 55% to 4.7 µM from the baseline. The average concentration of nitrate was reduced by 17% and ammonia by 28% in the cenosphere-treated group. Hence, the cenospheres were effective in reducing the concentrations of all three pollutants, with the greatest reduction seen for nitrite. These findings support further investigation for incorporating TiO2 cenospheres into aquarium filtration to help reduce the environmental burden of the aquarium industry