Browsing by Author "Ng, Kelvin Tsun Wai"

Now showing 1 - 20 of 22

Open Access
An evaluation on electronic waste management and product stewardship programs in North America
(Faculty of Graduate Studies and Research, University of Regina, 2023-12) Hasan, Mohammad Mehedi; Ng, Kelvin Tsun Wai; Jin, Yee-Chung; Na (Jenna)
Electronic waste (E-waste) has been extensively investigated by researchers throughout the globe, however specific research trends in North America (NA) are yet unknown. The first part of the study attempts to present an up-to-date bibliometric view of e-waste studies and to identify the research sub-fields and networks. A total of 271 documents were retrieved from the Web of Science (WoS) database (from 2001 to 2022). E-waste research topic that originated from NA, as well as its relative growth rate, collaborative measures, institutional productivity, and the popular journals were evaluated in this bibliometric analysis. The first part of the study showed that research productivity increased noticeably in the last decade. The USA has the most e-waste publications (74.62%), followed by Canada (22.38%) and Mexico (10.44%). The topic with the highest percentage of papers (151, or 55.72%) was environmental science. Resources Conservation and Recycling was the most active journal on e-waste research. The University of California, USA (10.70 %) played an active role in the publication, and Ogunseitan, O. A. was the most productive author (4.80 %) in this field. Author’s keywords can be generally grouped into four clusters. Network analysis results suggest that collaborative activities by leading universities will likely boost the number of studies. Researchers and policymakers will benefit from the first part of the study by gaining a better understanding of the development and the content trends of e-waste research. It is found in Part 1 that e-waste stewardship studies in Canada are limited, and they are specifically addressed in part 2. The amount of e-waste generated worldwide is growing at an explosive rate. The precious materials contained in this waste stream offers an ample business opportunity that produces high returns for the recyclers both in informal as well as formal sectors. A range of e-waste recycling companies have proliferated not only in developing countries but also in industrialized nations. The second part of the study further analyzed and evaluated e-waste management performances and recycling practices of a Canadian company that operates throughout the country. The company’s annual performance report from 2012 to 2020 served as the source for the e-waste statistics and related materials for the second part of the study. The corporate website is also considered in addition, to gain an overall understanding of the business portfolio. Temporal variations of performance factors were examined, and regression analysis was carried out to assess the relationships among various elements related to the recycling features. The study findings show that the overall e-waste collection rate throughout the country plummeted dramatically during the course of the investigation starting from 1.1-5.04 kg/capita to 1.4-3.0 kg/capita. E-waste drop-off points designated by the company have expanded by more than 800% and industry participation rose to more than 120% during the study period. Furthermore, study reveals that around 77% people in Canada are aware of the e-waste management and 97% people remain very close to the authorized e-waste collection points. The outcomes disclose that there is no overall correlation between public awareness and the rate of stewardship registration or e-waste collection. With just a few minor variations, the company's sector-specific yearly spending allocation over the investigation period was nearly identical. Corporation’s average total recycling expense ranges from $1,290 in 2012 to $1,578 in 2020. The outcomes of the current study can potentially inform recycling entrepreneurs and policy makers crafting methodical and strategic plans for the adoption of e-waste formalization management systems.
Open Access
Analysis and optimization of Ozone Assisted Biological Filtration Systems Used in Surface Water Treatment,
(Faculty of Graduate Studies and Research, University of Regina, 2014-03) Zanacic, Enisa; McMartin, Dena; Stavrinides, John; Jin, Yee-Chung; Ng, Kelvin Tsun Wai; McCullum, Kevin
Small and rural communities across Canada depend on potable water sources that are collected in farm dugouts or small reservoirs. In Saskatchewan, the village of Osage and Hamlet of Benson are two communities that depend on farm dugouts for their drinking water supply. Within the last 10 years both communities implemented ozone-assisted biological filtration for water treatment; however, both plants experienced low treatment efficiency, as indicated by presence of disinfection by products and in particular trihalomethanes at concentration that exceeds Saskatchewan Drinking water standards of maximum acceptable concentration (MAC) of 100 μg/L as a running annual average of seasonal samples. Over a 14 months period water treatment plant performance at both communities was monitored and analysed along with water quality. Water samples were collected through the treatment train every two months and analysed for a large number of water chemistry parameters. From water quality results ozone efficiency was assessed. Microbiology of the water sources at both communities in fall and early spring was analysed. Analysis of microbiology of biologically activated carbon filter media collected in fall at Village of Osage was performed. Water chemistry and performance at both plants indicates that raw water quality is the major obstacle to the efficient plant performance. High alkalinity (bicarbonate, carbonate and phenol) as well as salinity seem to inhibit / scavenge the ozone so that oxidation of organic matter is not adequate. Fluctuations in the turbidity of the water make the operation of the plant very challenging and filters requires frequent backwash. Microbiology of the dugouts suggests that salinity of the dugouts govern microbiology of the dugouts as well. Even though both dugouts have bacterial communities with identical phylum, the species richness of the each phylum is different between the two dugouts. Microbiology of the filters showed decline of drinking water pathogens through the filter except for two bacterial genera Legionella and Campylobacter. Both genera are opportunistic pathogen with potential to cause respiratory and gastro intestinal infections especially in immunocompromised (seniors, children, ill) population. Most of the pathogens identified here if not all are susceptible to disinfection, chlorination in particular. However, it is recommended that at peoples’ homes hot water tanks are keep the water temperature at or above 60 ºC and cold water tanks are set at less than 20 ºC to minimize survival of Legionella in piping and faucets. Potential improvement in design and layout of the filters is identified. Filters should be configured so that the contaminant removal from the drinking water is maximized. That can be achieved with installation of up-flow dual or multimedia roughing filter to reduce turbidity and connecting filters in series in order to maximize the contaminant removal from the drinking water. The first step in improvement of efficiency for the water treatment plants employing ozone assisted biological filtration is to outline and design a buffer zone around dugout. Next step would be to optimize the ozone dose for DOC removal as well as outfitting the plant filters design and layout to meet the degrading water quality of the source that is being treated. Finally, disinfection of the water must not be neglected or compromised in order to meet regulatory standard on disinfection by product.
Open Access
Analysis and prediction of traffic accidents at urban intersections
(Faculty of Graduate Studies and Research, University of Regina, 2023-11) Shikder, Md Ferdousul Haque; Tang, Yili; Ng, Kelvin Tsun Wai; Sharma, Satish
Traffic accidents generate significant harm, injuries, and fatalities on a global scale, making their investigation an important topic of study. In the initial phase of the study, we examine the influence of three micro traffic parameters, namely standstill distance, headway duration, and following distance oscillation, on both traffic flow and intersection safety. A data-driven approach is proposed for identifying the Pareto optimal sets of parameter combinations that both maximise the flow volume and minimise the risk of crashes. The analysis of traffic flow is conducted by considering different scenarios involving standstill distances ranging from 0 to 5 metres, headway times of 0.5 seconds, 0.9 seconds, and 5 seconds, as well as following distances spanning from 1 to 10 metres. The trajectories derived from the microsimulation model are further examined using the surrogate safety assessment model to ascertain the distribution of time-to-conflict between vehicles. This analysis facilitates the estimation of risk for crash by employing extreme value theory. The findings from the case study of Lewvan Drive and 13th Avenue intersection suggest that utilisation of headway times of either 0.5 or 0.9 seconds, in conjunction with standstill distances exceeding 2 metres and following distance fluctuations ranging from 1 to 9 metres, guarantees the mitigation of crash risks to a minimum level, while simultaneously resulting in maximum traffic flows. The subsequent phase of the research endeavours to construct dynamic forecasts of accident rates at intersections by taking macro traffic variables into account. Additionally, it evaluates the predictive efficacy of statistical models, machine learning methods, and neural network algorithms. The initial step involves conducting Pearson's correlation and statistical analysis to ascertain the associations between the macro variables, namely the number of accidents, average daily traffic on weekdays for major and minor roads, number of legs at the intersection, traffic signal conditions, intersection location, and peak hours. A threshold value of 0.7 is employed to verify the existence of collinearity among the variables. Based on the correlation analyses, the study further employs prediction models of three streams, including statistical analysis (Negative Binomial Model), machine learning algorithm (ARIMA Model), and neural network (Multi-Layer Perceptron Model). All models leverage a common dataset, which is transformed into an hourly time series prior to the application of the models. The results of this study underscore the progress made by various prediction algorithms in accurately anticipating the incidence of traffic accidents at crossings, as well as the interrelationship between traffic volume and signal characteristics. The study's findings offer valuable insights and a framework for policymakers to effectively implement safety regulations and ensure satisfactory traffic flow. Additionally, these findings can aid in reducing accidents and optimising roadway capacity. Furthermore, the study provides valuable insights for drivers, helping them understand the importance of maintaining safe distances while driving and ultimately reducing risky manoeuvres while maximising traffic flow. Subsequently, the utilisation of the dynamic accident prediction model empowers policymakers to assess and forecast the efficacy of a safety measure with regards to factors such as traffic volume and intersection control through a comparative analysis of the changes in the variables both before and subsequent to the implementation of the intervention.
Open Access
Analytical Coupling Methodology of Fluid Flow in Porous Media Within Multiphysics Domain in Reservoir Engineering Analysis
(Faculty of Graduate Studies and Research, University of Regina, 2020-01) Yuan, Wanju; Zhao, Gang; Jin, Yee-Chung; Jia, Na; Ng, Kelvin Tsun Wai; Chi, Guoxiang; Moore, Robert G.
Fluids flow in porous media are usually affected by multiphysics domains. Thermal, mass transfer, and hydraulic domain will all significantly affect the features of fluids flow in porous media. Thermal fluids coupling problems occur almost in every area of reservoir engineering such as geothermal energy development, and heavy oil recovery. Mass transfer is another important mechanism that should be considered in solvent based heavy oil recovery and unconventional enhance oil recovery methods. This research focuses on using analytical source and sink function method applied in heat transfer and mass transfer to simulate two domain coupling model. Based on thermal source and sink function derived in this thesis, convective heat is treated as a simple special form of source and sink function. The calculation of transient convective heat amount in Laplace domain problem has also been solved innovatively in this dissertation. Sensitivity analysis on segment size from computing prospect, thermal diffusivity and velocity from system prospect are analyzed to help understand the heat transfer process integrating conduction and convection mechanism. Secondly, this convective source function methodology is applied in a 2D model of geothermal energy recovery process. A typical geothermal energy recovery well pair is simulated by the innovative coupling methodology. Different well pair locations and fractured wells are examined through this model referring to the enhanced geothermal system technology for hot dry rock reservoir. Big jumps from heat transfer to mass transfer are made to analytically model the solvent injection process for heavy oil recovery. Multi-mechanisms including diffusion and dispersion, viscosity reduction, oil swelling are considered analytically and integrated into the two domain coupling model. Solvent-based Post Cold Heavy Oil Production with Sand (CHOPS) with single fracture structure is also modeled by this methodology. The mass transfer proves to have significant influence on fluids flow in porous media. Heavy oil thermal based recovery methods such as SAGD have complicated interactions phenomenon between thermal domain and pressure domain. Viscosity reduction, fluids thermal expansion and heat loss to caprock will significantly affect the operation energy efficient and environment footprint. Sensitivity analysis of key parameters affecting the thermal injection process are also conducted.
Open Access
Analytical Model for Fluid Flow Coupling With Heat Transfer Integrating Heat Conduction and Convection in Radial System
(Faculty of Graduate Studies and Research, University of Regina, 2015-09) Yuan, Wanju; Zhao, Gang; Gu, Yongan (Peter); Ng, Kelvin Tsun Wai; Yao, Yiyu
Enormous heavy oil resources has been found in western Canada. But some factors especially high viscosity limit their development. Thermal recovery methods which injecting heat into the reservoir or in-situ combustion, have been widely used to enhance heavy oil recovery. The viscosity of the crude oil has been lowered by raising the temperature of the reservoir, so temperature and pressure profiles are important factors for making operations and development plans in thermal recovery process. Understanding how heat transfer influences the fluids flow is the key knowledge for us to make the right decisions. In this study, a novel heat transfer model in radial system, integrating both conduction and convection, has been developed to describe the heat transfer in the heating reservoir. In this temperature domain model, heat injection rate keeps constant and dimensionless variables are defined to reduce the model to the dimensionless form. Variable transformation and Laplace transformation are performed to derive the analytical solution in Laplace space. By using Stehfest inverse algorithm, the solution in Laplace space can be converted to dimensionless analytical solution in real time space. With an analytical solution of temperature domain, fluid flow in the reservoir can be generated by dividing the whole reservoir into numbers of sub-sections. Pseudo-time is introduced to solve the changing viscosity and makes the analytical model can be solved. Dimensionless variables are also defined and the pressure are solved in Laplace space. Sequentially coupling method is applied to use the temperature profiles in pressure domain. The final dimensionless analytical solutions are obtained by Stehfest inverse algorithm. Numerical simulations by COMSOL Multiphysics are conducted to validate the analytical solutions of the models. Satisfactory agreements of the results are achieved between analytical solutions and numerical simulation results. Sensitivity analysis are also conducted to analyze the influence factors of heat transfer and fluid flow. Heat injection rate, heat capacity of fluids and rock, permeability are important parameters for heat
Open Access
Assessing construction and demolition waste generation rates using satellite imagery
(Faculty of Graduate Studies and Research, University of Regina, 2024-04) Ray, Sagar; Ng, Kelvin Tsun Wai; Veawab, Amornvadee (Amy)
Municipal solid waste management has seen a surge in the use of satellite imagery in decision-making processes, yet its application to analyze quantitative variations in construction and demolition (C&D) waste remains underexplored. Especially the COVID- 19 pandemic disrupted conventional municipal solid waste (MSW) management practices and affected waste generation rates. While MSW streams have been extensively studied and reported, the impact on construction and demolition (C&D) waste remains overlooked. As such, the first part of the study develops an innovative analytical framework utilizing satellite imagery to quantify C&D waste disposal rates during COVID-19 restrictions in a mid-sized Canadian city. Supervised classification of Landsat-8 images is conducted to derive the settlement area over a period of 8.8 years (2014-2022). The relationship between C&D disposal rates and settlement area is evaluated using regression analysis. Results reveal a 73.4% reduction in mean weekly C&D disposal in 2020 compared to pre-pandemic years, reflecting diminished construction activity. The settlement area exhibits a strong positive correlation (R2=0.812) with per capita C&D disposal rate, providing spatial evidence of urbanization patterns affecting C&D waste generation. Among socioeconomic factors examined, the value of building permits issued most influences C&D quantities (R2=0.934). The satellite imagery-based approach allows indirect estimation of disrupted C&D waste streams when on-site auditing is restricted during pandemics. The framework offers municipal authorities spatial decision support to formulate data-driven C&D waste management policies that are resilient to future public health emergencies. The second part of the study employs satellite imagery and multivariate analysis to comprehensively assess and predict C&D waste generation in four diverse urban jurisdictions of Canada (Regina) and the USA (Seattle, Buffalo, and Philadelphia). In Seattle, the annual mean C&D waste amount per capita is 0.624 tonnes, while in Regina, Buffalo, and Philadelphia, it is 0.224, 0.330, and 0.014 respectively. Factors such as settlement area expansion, economic activities, and population growth significantly influence C&D waste rates. Stepwise multivariate regression models tailored to different city types, such as moderately populated (Group 1) and highly populated (Group 2), showcase acceptable predictive capabilities. For moderately populated cities, settlement area, average humidity, and GDP are identified as key predictors, while for highly populated cities, settlement area, unemployment rate, and building permit value prove effective indicators. These models, characterized by R² values from 0.70 to 0.94, provide tailored insights for distinct demographic conditions, aiding waste management planning. This research underscores the importance of satellite imagery and multivariate analysis in understanding C&D waste dynamics and empowers policymakers and waste management agencies with evidence-based strategies for effective waste management in urban centers.
Open Access
Characterization and Centrifuge Dewatering of Oil Sands Fine Tailings
(Faculty of Graduate Studies and Research, University of Regina, 2013-08) Rima, Umme Salma; Azam, Shahid; Henni, Amr; Ng, Kelvin Tsun Wai; Cheema, Tariq
Oil sands mining operations in northern Alberta, Canada generates an ever growing volume of fine tailings that are disposed off hydraulically in the tailings ponds. The caustic extraction process results in dispersed tailings that do not dewater under conventional gravity settling. Centrifugation along with polymer addition has recently demonstrated promising results for these tailings at the pilot-scale level. The complex colloid-water-polymer interactions govern the dewatering behaviour of the tailings during this process. The main objective of this research was to characterize and improve the dewatering properties of oil sands fine tailings using centrifuge technology in conjunction with polymer amendment. MFT was found to be a fine grained material with clay size fraction of 53% and possessing a moderate water adsorption capacity (wl = 55% and wp = 25%). The solids comprised of 55% quartz and 40% clay minerals (kaolinite and illite) and showed a specific surface area of 43 m2/g and a cation exchange capacity of 29 cmol(+)/kg. Likewise, the pore water was dominated by Na+ (776 mg/L) and HCO3 - (679 mg/L), related to the extraction process and by Cl- (518 mg/L) and SO4 2- (377 mg/L), related to ore geology. A basic pH (8.15), a high EC (3280 μS/cm), and a high ZP (-46 mV) indicated a dispersed MFT microstructure. Centrifugation improved MFT dewatering through the physical mechanisms of particle segregation, assemblage formation, and flow channeling. For the investigated g-factor of up to 2550 g, the released water increased by 4.7%, the entrapped water decreased by 30% and the sediment solids content increased by 7%. The corresponding decrease in pH was from 8.15 to 7.2, EC from 3295 μS/cm to 2530 μS/cm, and ZP from -40 mV to -28.7 mV. These data confirmed aggregate formation and an effective capture of clay particles mainly in the intermediate suspension zone. Centrifugation along with polymer amendment was found to improve MFT dewatering up to 630 g (because of assemblage formation due to increased particle collisions and polymer adsorption) beyond which dewatering declined (owing to floc breakage due to excess centrifugation and surface saturation). For 10 mg/L polymer, the released water increased by 17%, the entrapped water decreased by 58% and the sediment solids content increased by 13%. The corresponding values at 20 mg/L were found to be 34%, 82%, and 18%, respectively. The physicochemical parameters were found to correlate well with tailings dewatering. The decrease in pH, EC, and ZP up to 630 g is due to water dilution, charge neutralization, and shear plane displacement, beyond which opposite phenomena occurred. At the optimum and 10 mg/L polymer, the pH value decreased to 7.5, EC decreased to 2615 μs/cm, and ZP decreased to -26 mV. The corresponding values at 20 mg/L were found to be 7.5, 2234 μs/cm, and -21 mV, respectively.
Open Access
Chloride Salts Removal by non Planted Constructed Wetlands Receiving Synthetic Brines from Belle Plaine Potash Mining
(Faculty of Graduate Studies and Research, University of Regina, 2015-03) Chairawiwut, Warawut; McMartin, Dena; Azam, Shahid; Ng, Kelvin Tsun Wai; An, Chunjiang; Gilles, Jon
Four pilot-scale constructed wetlands (CWs) were employed to study the fate and transport of the two dominant chloride salts (NaCl and KCl) receiving the synthetic brine. The characteristics of the brine solution are made up with a 10:1 concentration ratio between NaCl and KCl based on data obtained from Belle Plaine potash mine site. The multi-layer soils were designed to function as a main salt filtering component comprising of Regina Clay (grain size <0.002 mm), Brick Sand (grain size <4.75 mm) and sharp gravels (grain size between 6.3-19.1 mm) despite the clay layers contained a poor compact condition (Db =1.4, <1.6 g/cm3). The volume of void space in the compacted clay was reduced to approximately half the natural state following application of pressure (4,505 cm3 to 2,743 cm3). The CW systems were operated by the 16-day format (batch 1-3) and the 4-day format (batch 4). During the 16-day format experiments, the best K+ removal rate was recorded on Cell2 as 92.1±63.4% (4.6±5.3mg/l) while Cell 4 contributed the maximum removal of Na+ and Cl- as 44.8±76.7% (53.2±92.4mg/l) and 50.5±109.6% (85.3±184.3.4mg/l). In the 4-day format operation, the chloride breakthrough curve was discovered in all treatment CW cells, excluding the control. Moreover, the curve stated at less than 6 hours (C/C0 > 0.05) and approximately reached the break point (C/C0 > 0.95) after passing 48 hours. Then the clay media was exhausted and lost its ability to remove Cl-. However, the study was not able to determine the breakthrough curves in neither Na+ nor K+ cases during batch experiment 4 due to unidentified ending points on both cations.
Open Access
Corrosion Inhibition Performance of Methionine for CO2 Absorption Plants
(Faculty of Graduate Studies and Research, University of Regina, 2021-03) Udayappan, Balaji; Veawab, Amornvadee; Ng, Kelvin Tsun Wai; Aroonwilas, Adisorn; Muthu, Jacob
Inorganic corrosion inhibitors including heavy metals have been widely used in the carbon dioxide (CO2) absorption process for corrosion control. However, they are not environmentally friendly causing costly handling and disposal costs. This work therefore evaluated corrosion inhibition performance of an organic amino acid compound, namely Methionine (MTI) which is less toxic, more readily biodegradable, and has lower potential for bioaccumulation in aquatic organisms compared to common amine absorption solvents. The evaluation was experimentally implemented using electrochemical and weight loss methods. Carbon steel (CS1018) and 5.0 kmol/m3 Monoethanolamine (MEA) purged with 85% CO2 and 15% oxygen (O2) were used as tested material and absorption solution, respectively. The electrochemical results showed that at solution temperatures up to 80oC, MTI effectively reduced corrosion rates of CS1018 with maximum inhibition efficiencies of 83.56% ± 1.82% under a static condition (0 rpm) and 74.96% ± 0.95% under a dynamic condition (1500 rpm). Its inhibition performance was found to increase with inhibitor concentration and solution temperature but decrease with rotational speed. MTI acted as a mixed-type inhibitor and exhibited pitting tendency. The optimal MTI concentrations were 1500 ppm at 0 rpm and 2000 ppm at 1500 rpm. The post data analysis involving adsorption isotherm and activation thermodynamic properties revealed that MTI protected metal surface by undergoing spontaneous and endothermic physical adsorption. Its adsorption characteristic matched well with the Langmuir adsorption isotherm, thereby suggesting that MTI formed a protective monolayer on the metal surface. The results of quantum chemical analysis suggested MTI has higher affinity, polarizability, and electron donating ability than MEA. III The results of weight loss experiments carried out for up to 28 days showed that at 120oC, 5 bar and 1500 rpm, MTI was able to reduce corrosion rates of CS1018 to below 1 mmpy. The inhibition efficiencies were up to 78.7% for carbon steel specimens fully immersed in the MEA solutions, 53.5% for those partially immersed in the MEA solution and partially exposed to vapor, and 85.6% for those fully exposed to vapor. Pits were observed on carbon steel specimens fully immersed in both uninhibited and MTI inhibited solutions.
Open Access
Effects of a global pandemic on the collection and disposal of municipal solid waste
(Faculty of Graduate Studies and Research, University of Regina, 2023-06) Mahmud, Tanvir Shahrier; Ng, Kelvin Tsun Wai; Xue, Jinkai; Khan, Sharfuddin; Lozecznik, Stan
The COVID-19 pandemic and the subsequent lockdowns had significant effects on solid waste management, which has received greater research focus during this time due to the infectious nature of the SARS-CoV-2 virus. As such, in the first part of the study, SARIMA models were developed to predict residential waste collection rates (RWCR) across four North American jurisdictions before and during the pandemic. Unlike waste disposal rates, RWCR is relatively less sensitive to the changes in COVID-19 regulatory policies and administrative measures, making RWCR more appropriate for crossjurisdictional comparisons. It is hypothesized that the use of RWCR in forecasting models will help us to better understand the residential waste generation behaviors in North America. Both SARIMA models performed satisfactorily in predicting Regina's RWCR. The SARIMA DCV model's performance is noticeably better during COVID-19, with a 15.7% lower RMSE than that of the benchmark model (SARIMA BCV). The skewness of overprediction ratios was noticeably different between jurisdictions, and modeling errors were generally lower in less populated cities. Conflicting behavioral changes might have altered the residential waste generation characteristics and recycling behaviors differently across the jurisdictions. Overall, SARIMA DCV performed better in the Canadian jurisdiction than in U.S. jurisdictions, likely due to the model's bias on a less variable input dataset. The use of RWCR in forecasting models helps us to better understand the residential waste generation behaviors in North America and better prepare us for a future global pandemic. The second part of the study aims to identify the effects of continued COVID-19 transmission on waste management trends in a Canadian capital city, using pandemic periods defined from epidemiology and the WHO guidelines. Trends are detected using both regression and Mann-Kendall tests. The proposed analytical method is jurisdictionally comparable and does not rely on administrative measures. A reduction of 190.30 tonnes/week in average residential waste collection is observed in the Group II period. COVID-19 infection negatively correlated with residential waste generation. Data variability in average collection rates during the Group II period increased (SD=228.73 tonnes/week). A slightly lower COVID-19 induced Waste Disposal Variability (CWDV) of 0.63 was observed in the Group II period. Increasing residential waste collection trends during Group II are observed from both regression (b = +1.6) and the MK test (z = +5.0). Both trend analyses reveal a decreasing CWDV trend during the Group I period, indicating higher diversion activities. Decreasing CWDV trends are also observed during the Group II period, probably due to the implementation of new waste programs. The use of pandemic periods derived from epidemiology helps us to better understand the effect of COVID-19 on waste generation and disposal behaviors, allowing us to better compare results in regions with different socio-economic affluences. The results of both studies will assist policy makers in developing data-driven solid waste management policies during a global pandemic.
Open Access
Enhanced Physicochemical Processes for the Treatment of petroleum-Contaminated Systems
(Faculty of Graduate Studies and Research, University of Regina, 2015-09) Zhao, Shan; Huang, Guo H.; Ng, Kelvin Tsun Wai; An, Chunjiang; Deng, Dianliang; Song, Lianfa
In Canada, environmental issues caused by petroleum-contaminated sites are becoming a major concern. Therefore, effective physicochemical remediation technologies are desired for produced water treatment and groundwater remediation in oil fields. In this dissertation research, the feasibility of treating produced water using synthetic polymers combined with natural diatomite was evaluated. Using diatomite as an adsorbent and a coagulant aid, this study provided an economical and enhanced approach for utilizing diatomite in the clean-up of produced water. A pilot-scale electrocoagulation process was developed for enhanced removal of hardness, chemical oxygen demand, and turbidity to mitigate the scaling and fouling of Reverse Osmosis membranes. Response surface methodology was employed to refine operating parameters and to evaluate individual/interactive effects of parameters on pollutant recovery. The modification of palygorskite with gemini surfactants enhanced phenanthrene retention in solid particles from aqueous phase. The effects of solution chemistry on phenanthrene sorption to modified palygorskite were systematically studied. The effectiveness of gemini modified palygorskite as the novel remediation material in polycyclic aromatic hydrocarbon contaminated water remediation was revealed and examined. A multi-level fuzzy-factorial inference approach was proposed to elucidate the sorption behavior of phenanthrene on palygorskite modified with gemini surfactants. Fuzzy vertex analysis discretized the design factors with triangular membership functions into multiple deterministic levels. Examination of curvature effects of factors revealed the nonlinear complexity inherent in the sorption process. The potential interactions among experimental factors were detected, which was meaningful for providing a deep insight into the sorption mechanisms under the influences of factors at different levels. The enhancement of soil retention for phenanthrene was investigated through the sorption barriers created by binary mixture of cationic gemini and nonionic surfactants. The research addressed the sorption characteristic and mechanism of gemini surfactant in complex soil system using a developed Two-step Adsorption and Partition Model. The sorption barrier substantially enhanced the soil retention capabilities for phenanthrene, while the sorption of gemini was inhibited by the increasing nonionic surfactant dose. The interactions among water, soil, surfactant, and contaminant in petroleumcontaminated systems have been revealed. This research can provide reference on the implementation of remediation technologies at petroleum-contaminated sites.
Open Access
Evaluation of Contaminant Containment at Regina Landfill
(Faculty of Graduate Studies and Research, University of Regina, 2014-03) Frederick, Joshua; Jin, Yee-Chung; Ng, Kelvin Tsun Wai; Young, Stephanie; Bayer, Sean
Landfill and waste containment facilities are routinely constructed on natural or engineered low permeability barriers placed above or within the vadose zone to prevent contaminant migration into the groundwater system. Numerical estimates of design lives for assessment of barrier system performance are generally acceptable under numerous landfill regulations. Predictive models work under the general assumption that constructed systems will retain their structural integrity over the design life of the landfill and act as leak proof systems. Contrary to the above assumption, barrier performance, whether natural or engineered, at countless landfills and waste disposal sites across North America suggests that these liners tend to act as leak-resistant, and not leak-proof, systems. Across Canada, the designs of these barrier systems at various landfill sites are typically governed by prescriptive engineering design standards as opposed to performance or risk-based standards set by the regulatory agency having jurisdiction over the landfill. This study investigates the contaminant containment potential of a composite landfill liner system in conjunction with the naturally occurring glacioacustrine clay barrier at the Regina landfill expansion site. Transit time was calculated for the different landfill design types as prescribed under the Saskatchewan Environment Code (SEC) and compared to simulations using two commercially-available, one-dimensional modeling software packages. VZCOMML© a one-dimensional, steady-state, equilibrium partitioning vadose zone model that uses a multi-layered soil column was used to simulate advective flows; and CHEMFLUX, a one-dimensional model to simulate diffusion. The results suggest that inherent low permeability property of the native barrier underlying the landfill is adequate to prevent potential contamination of groundwater over the “contaminating life span” (Rowe, 2005) of the landfill expansion area. However, the natural barrier has finite hydraulic conductivity and ultimately, over long periods of time, breakthrough will occur due to diffusion. The literature review and modeling investigation indicate that more attention should be directed towards active contaminant removal, treatment, and disposal as opposed to pure contaminant containment at landfill sites over their design life. There seems to be overemphasis on dry tomb designs focused on contaminant containment, liner effectiveness, and review of hydrogeological aspects as key landfill performance indicators. With current trends in innovation and evolution in landfill technologies, landfills should be viewed as solid waste processing facilities and not waste burial sites. This study hypothesises that a systems approach to design and performance evaluation centered on total lifetime contaminant mass management would be more ideal for the Regina Landfill site.
Open Access
Forecasting waste volume and identifying barriers of Canadian photovoltaic waste management
(Faculty of Graduate Studies and Research, University of Regina, 2022-09) Romel, Monasib Ahmed; Kabir, Golam; Ng, Kelvin Tsun Wai; Khondoker, Mohammad; Ruparathna, Rajeev
The worldwide exponential upsurge of photovoltaic (PV) installations and the subsequent heights of PV waste is a swelling apprehension. The objectives of this study are to forecast the photovoltaic waste volume and to analyze the critical barriers for the photovoltaic waste management in Canada. In the first section, the solar waste volume forecasting was done using linear regression, 2nd order polynomial regression, and power regression models. In the second section, the barriers to photovoltaic solar waste management were identified through literature review and analyzed by formulating a framework from integrating Rough Analytical Hierarchy Process (RAHP), Decision-Making Trial and Evaluation Laboratory (DEMATEL) and Interpretive Structural Modeling (ISM) methods. The findings of the thesis show that for early loss the PV waste volume will be as high as 270,000 MT and as low as 180,000 MT and for regular loss the PV waste volume will be as high as 180,000 MT and as low as 160,000 MT for the year of 2045. The result of the barrier analysis shows that a complex causal relationship exists among the barriers with “Insufficient Generation of PV Waste”, and “Waste Collection Centre” are the top two crucial barriers with highest driving power and causal effect on others. This thesis is expected to contribute to the concerned government agencies to assess the upcoming volume of PV waste and then evaluate the relationship among the barriers to PV waste management for establishing a sustainable and resilient PV waste management plan for Canada.
Open Access
Investigating The Impacts of Adverse Road Weather Conditions on Free-Flow Speed and Lane Utilization
(Faculty of Graduate Studies and Research, University of Regina, 2018-11) Rillagodage, Navoda Yasanthi; Sharma, Satish; Mehran, Babak; Jin, Yee-Chung; Ng, Kelvin Tsun Wai; Peng, Wei
Winter driving poses additional safety challenges to drivers and other road users due to reduced visibility, snow and ice accumulation on travel lanes, and variations in transportation infrastructure such as reduced lane width due to snow plow operations and coverage of lane markings by snow. On the other hand, road-weather related variations in transportation infrastructure characteristics and driver behavior negatively impact traffic operations in winter. Therefore, it is crucial to understand the anticipated consequences of extreme road-weather conditions on traffic flow parameters and driver behavior. Thus, in this study, the free-flow speed and the lane utilization patterns under adverse roadweather conditions were studied. Road-weather data were collected from a Road-Weather Information System (RWIS) and traffic data were collected from a Weigh-In-Motion (WIM) station located in Highway 16 in Alberta from October, 2014 to December, 2015. The first part of the study attempts to investigate drivers’ choice of desired speed under adverse road-weather conditions with two main objectives: i) to model the impacts of road-weather events on free-flow speed of light and heavy vehicles, and ii) to explore the variability in free-flow speed models caused by adopting different data analysis methods. Separate linear and nonlinear regression models were developed by adopting three distinct statistical approaches i.e. i) with dependent variable as individual vehicle speeds, ii) with dependent variable as 20 minute aggregate vehicle speeds, and iii) with sampled data. The study results revealed that slight, moderate and heavy snow will reduce the free-flow speed of light vehicles travelling in shoulder lane by 0.2%, 3.4% and 0.8% and the free-flow speed of heavy vehicles by 1.7%, 0.1% and 1.3% respectively. Further, it was unveiled that the drivers’ reaction to ice warning pavement surface conditions is maximum. Linear regression models with aggregated speeds as the dependent variable was concluded as the best fit for the data among the other statistical approaches tested. The second part of the study aims to model lane utilization patterns of light and heavy vehicles under different road-weather conditions in macroscopic and microscopic facets. Two main types of lane utilization models were developed exerting a linear and a logistic regression approach in modelling. Each main model contains three sub models with refined data corresponding to all light and heavy vehicles. Interestingly, moderate rain and nighttime cause the vehicles to prefer shoulder lane irrespective of the vehicle type as suggested by both models. The findings indicated that heavy vehicles tend to choose the median lane under icy pavement conditions as estimated by both model types. Light vehicles tend to utilize the median lane under ice watch and frost pavement conditions in macroscopic and microscopic contexts, respectively. Unlike the other similar studies conducted so far, this study estimates the free-flow speeds and lane utilization patterns of vehicles more accurately because of the unique location configuration of the data collectors. In addition, the study results direct the weather responsive traffic management systems to a new path by introducing more dimensions to be considered about, such as variable speed limits depending on different road-weather conditions and traffic composition, and dynamic lane utilization schemes.
Open Access
Irrigation Water Requirements under Climate Change and Drought Events in Saskatchewan,
(Faculty of Graduate Studies and Research, University of Regina, 2015-03) Kraemer, Evan Matthew; Hodder, Kyle; McMartin, Dena; St. Jacques, Jeannine-Marie; Ng, Kelvin Tsun Wai; Helgason, Warren
This research considers the effects of climate change projected by global climate models (GCMs) on irrigated agriculture and water supply in Saskatchewan using 27 different combinations of GCMs, special reports on emissions scenarios (SRES), and time periods (2020s, 2050s, 2080s). Future drought events are extracted from the scenarios using the Standardized Precipitation-Evapotranspiration Index (SPEI) to identify extremely dry conditions, and downscaled to create a daily time-series of temperature and precipitation. The CROPWAT agroclimatic model is used to calculate irrigation water requirements (IWR) under given conditions for two crops commonly grown in rotation, canola and dry beans. This process allows for analysis of current and future water demands for irrigated agriculture. Under future drought conditions, IWR changes are found to be from -10% to 20% relative to the 2001-02 drought event. The resulting water requirement from Lake Diefenbaker, including irrigation expansion to 200 000 ha, is up to 12% of annual supply volume for irrigation.
Open Access
Numerical Modeling of the Dam-Break on a Slope Channel by WC-MPS Method
(Faculty of Graduate Studies and Research, University of Regina, 2015-09) Bakouie, Masoud; Jin, Yee-Chung; Ng, Kelvin Tsun Wai; Ismail, Mohammed
Numerical simulation methodologies have become a major approach for solving hydrodynamics problems over the past few decades. Due to their flexibility and adaptability, these methods can be employed in various subjects of engineering and science. These simulations are capable of providing the required knowledge to interpret the natural phenomena and as well can be an alternative means to study the theories and experiments. Numerical modeling of fluid flow can be categorized into two major approaches, mesh-based methods and mesh-free methods. Mesh-based methods used to be the dominant methods through the decades but their lack of success in the precise simulation of flow problems with considerable deformation and fragmentation resulted in the development of mesh-free methods. Mesh-free methods use a set of discrete particles and the field variables are assigned to each particle separately. As a result, the movement of the particles is a direct expression of the movement of the real physical system. Mesh-free methods have proven to be a robust tool in numerical simulation and yet to their fully extended application in the hydrodynamics simulations. In this thesis the Weakly-Compressible Moving Particle Semi-implicit (WC-MPS) method is described and demonstrated for the simulation of the dam-break case with a high viscous fluid on different bed slopes. During this study, at first the WC-MPS was applied to a horizontal case and the model was later modified to numerically study the effect of bed slopes on the dam-break case. Furthermore, the process of gate removal at the initial stage of the dam-break case and its influence on the flow current development were investigated. This investigation demonstrated that the process of gate removal can have a considerable effect on the formation and development of flow current in a dam-break case. At last, the capability of WC-MPS model to simulate open channel flow problems is confirmed through a comprehensive comparison with analytical and experimental studies. The simulations in this thesis demonstrate that WC-MPS can be used as a robust tool in simulation of fluid flow especially in problems with large pressure gradients and fast varying fluid levels. To maintain stability, a small time step is needed that unfortunately leads to considerable calculation time. To obtain an accurate simulation many particles should be employed, therefore the application of this method is restricted to local and short phenomena. Although WC-MPS is a relatively new technique in the field of computational fluid dynamics but it can be used in situations where many other methods fail, therefore its future looks promising.
Open Access
Numerical simulation and optimization of cyclic and continuous fluid injection for geothermal energy recovery
(Faculty of Graduate Studies and Research, University of Regina, 2023-07) Li, Runzhi; Jia, Na (Jenna); Zhao, Gang (Gary); Shirif, Ezeddin; Ng, Kelvin Tsun Wai
Geothermal energy is a viable solution for reducing greenhouse gas emissions and mitigating climate change. It has a wide geographic distribution, requires little exploration and operation costs, and has virtually no carbon emissions. This renewable energy source can generate electricity, provide direct heating and cooling, and even be utilized for agricultural and industrial processes. It can be harnessed at any scale, from individual buildings to large-scale power plants, and is available in many parts of the world. In addition, the operation and maintenance costs of geothermal energy resources are relatively low, making it a cost-effective alternative to other energy production forms. Meanwhile, geothermal energy emits significantly less carbon dioxide compared to fossil fuel power plants, reducing the dependence on fossil fuels. This thesis focuses on the numerical simulation of the geothermal energy extraction from the geothermal reservoirs by utilizing various recovery strategies originating from the petroleum industry. Initially, this research uses Computer Modelling Group (CMG) reservoir simulator software to simulate the energy extraction in the conventional water base geothermal reservoirs that locate at Western Canada Sedimentary Basin and the area in the City of Regina. The simulation of the primary recovery (rely on the natural energy release from the original reservoirs) and secondary recovery (continuous water injection and cyclic water injection) were discussed. The CMG-CMOST was involved in this study in order to process the optimization process to maximize cumulative energy production and net present value (NPV) of geothermal energy recovery process. In addition, the injected working fluid was changed to carbon dioxide (CO2) for extracting geothermal energy, which is considered a significant source caused global warming issues. In this study, the injected CO2 was controlled at a supercritical state in order to maintain its higher heat capacity. History matching was performed in order to verify the fluid model’s accuracy. All the simulation and optimization process was performed, and the performance of CO2 as a working fluid in the geothermal energy extraction process were discussed.
Open Access
Production of Furfural From Lignocellulosic Biomass Using Sulfonated Carbon-Based Solid Acid Catalysts
(Faculty of Graduate Studies and Research, University of Regina, 2021-12) Ogundowo, Oluwafadeyinmi Ibukunoluwa; Ibrahim, Hussameldin; Henni, Amr; Tontiwachwuthikul, Paitoon; Ng, Kelvin Tsun Wai
There is an aching desire to desist from the use of fossil fuel energy sources due to their major contribution to environmental degradation. Hydro, wind, and solar energy may serve as the much-needed alternative energy supply sources to fossil fuels however biomass will be the major alternative source for platform chemicals. Furfural is one of the 12 leading value-added chemicals identified by the US Department of Energy (DOE). It is of importance in the industrial sector, having applications such as; the removal of aromatics from diesel fuel and lubricant refining, and being a platform chemical from which a vast number of other chemicals are produced. The factors that influence furfural yield and selectivity are the catalyst used, solvent, catalysts loading, time, and temperature of the hydrolysis reaction. Farmers on the prairies have had a difficult time gathering and disposing of flax straws. Farmers burn this straw as a means of disposal due to its strong fiber and difficult decomposition. Every year, about 670,000 tonnes of flax straw are burned or destroyed on the prairies. This research work was aimed at the development of a sulfonated carbon-based solid acid catalyst for the production of furfural via hydrothermal hydrolysis of flax straw biomass. Glu-TsOH-Zr catalyst was developed, characterized by TGA, N2 -Physisorption, NH3-TPD, XRD, SEM, and FTIR, and then tested for its capacity in furfural production from flax straw biomass and pure xylose. Glu-TsOH-Ti and Glu-TsOH, replicated from literature were also characterized and applied for furfural production. The effect of residence time (0-120 mins), reaction temperature (170-210°), and the catalyst mass (0.25 -1g) on the furfural yield were also studied. Finally, the methyl tetrahydrofuran solvent ratio for optimal furfural production in a biphasic system was determined and a kinetic study was performed. The results presented that the Glu-TsOH-Zr catalyst had a good potential for improving furfural yield. The order of the catalysts based on the percentage of xylose conversion and furfural yield from pure xylose feed was Glu-TsOH-Ti > Glu-TsOH-Zr > Glu-TsOH. A reaction temperature of 190°C, a residence time of 120 minutes, and a catalyst mass of 1g (0.3 catalyst mass/flax straw mass) were found to be the best-operating conditions for furfural formation from flax straw biomass. The largest influence on furfural yield was determined to be temperature, followed by catalyst mass, and then reaction time. Furthermore, the catalyst with the highest overall acidity, surface area, and pore size (Glu-TsOH-Ti) also yielded the most furfural. The addition of an organic phase enhanced furfural yield, and the catalyst was reusable for up to three cycles with little drop in furfural yield; however, by the fourth cycle, there was a significant decrease in furfural yield. A first-order irreversible series reaction that started with the creation of furfural from xylose and ended with furfural degradation into degradation products was proposed as a kinetic model for the empirical rate data. The reaction leading to furfural production had higher activation energy (222.18kJ/mol) than the reaction leading to degradation products (104.56kJ/mol), showing that the furfural production reaction is more temperature-sensitive than the degradation reaction. Finally, the kinetic model's average absolute deviation (5.9%) indicated that it was an excellent fit for the reaction series.
Open Access
Simulation Study of Distillation, Stripping, and Flash Technology for an Energy Efficient Methanol Recovery Unit in Biodiesel Production Processes
(Faculty of Graduate Studies and Research, University of Regina, 2013-11) Philip, Firuz Alam; Veawab, Amornvadee; Aroonwilas, Adisorn; Ng, Kelvin Tsun Wai; Idem, Raphael; Zeng, Fanhua
Biodiesel is an important alternative renewable energy source currently produced by transesterification reaction of oil or fat with methanol. To improve the conversion, excess methanol is required, which must be recovered from the product stream and recycled back into the process for further biodiesel production. The intensive energy requirements for methanol recovery are an important issue that directly impacts the production costs of biodiesel. To reduce the cost of biodiesel production, an energy efficient methanol recovery unit (MRU) is crucial. This work focuses on energy requirement reduction by distillation, flash-based recovery, and newly-introduced stripping-based methanol recovery units. Four different continuous methanol recovery units were simulated using Aspen Plus. Energy requirements with respect to process parameters including percentage of methanol recovery, operating pressure, and methanol-to-oil ratio for all methanol recovery units were analyzed. Units were compared in terms of energy requirement and purity of recovered methanol product. The simulation results show that energy requirement for methanol recovery units increases with increase in % methanol recovery and reflux ratio (for distillation), but decreases with decrease in operating pressure and increase in methanol-to-oil ratio. The recovered methanol is pure for distillation and stripping-based MRUs. However, for flash-based MRUs, the purity of recovered methanol degrades at the high heat duty supplied. Consequently, the single- and double-flash-based MRUs have narrow ranges of operation. Moreover, double-flash-based MRUs have no significant advantages over single-flash-based MRUs in terms of heat duty. Comparison of heat duty among distillation, stripping, and single-flash reveals that the single-flash-based MRU is the most energy efficient followed by stripping and distillation-based MRUs.
Open Access
Spatiotemporal heterogeneity in precipitation and moisture transport over China and their connections with anthropogenic emissions and natural variability
(Faculty of Graduate Studies and Research, University of Regina, 2022-09) Lu, Chen; Huang, Guo (Gordon); Zhu, Hua; Ng, Kelvin Tsun Wai; Deng, Dianliang; Chen, Zhi
In this dissertation research, the following scientific questions are explored: (i) Has the probability distribution of precipitation over China undergone variations since the midtwentieth century? (ii) How are the above changes related to the modes of climate variability? (iii) Can these changes be attributed to anthropogenic behaviors? (iv) What are the mechanisms for these changes in terms of moisture transport and recycling? Specifically, through quantile regression, the quantile trends in monthly precipitation anomalies over China, as well as the individual and combined quantile effects of teleconnection patterns, are examined. The results show that the quantile trends exhibit apparent seasonal variations, with a greater number of stations showing trends in winter, and larger average magnitudes of trends at nearly all quantile levels in summer. The effects of El Niño–Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), and Pacific Decadal Oscillation (PDO) exhibit evident variations with respect to the quantile level. Spatial clusters are subsequently identified based on the quantile trends, and the individual and combined effects from the teleconnection patterns are further investigated from the perspective of moisture budget. Seven spatial clusters with distinct seasonal quantile trends can be identified; three of them are located in southeastern China and are characterized by increasing trends in summer and winter precipitation. Summer precipitation over this region is positively influenced by ENSO and negatively influenced by NAO, with the former affecting both the dynamic and thermodynamic components of vertically integrated moisture divergence and the latter affecting only the dynamic component. The interaction effect of ENSO and NAO on summer precipitation anomalies in extremely-wetter-than-normal months is statistically significant. The influences of anthropogenic greenhouse gas and aerosol emissions on the probability distribution of daily precipitation over China are explored through a formal detection and attribution analysis. It is found that the increasing trends in winter precipitation at high and extremely high quantile levels, as well as that in spring precipitation at all quantile levels, can be attributed to the effects of historical (ALL) or anthropogenic (ANT) forcing. The effect of anthropogenic greenhouse gas forcing (GHG) is evident over the domain, to which the increasing precipitation trends at all quantile levels in all seasons can be attributed; this effect can be separated from that of anthropogenic aerosol forcing (AER) for winter precipitation trends at high and extremely high quantile levels, and for spring, summer, and autumn trends at low quantile levels. Through integrating detection and attribution analysis and moisture tracking into one framework, the anthropogenic influence on the moisture source-receptor relationship over China is investigated. The subdomains of China can be grouped into 3 categories according to the major moisture sources, which are regions mainly dependent on (a) oceanic sources, (b) external terrestrial sources, and (c) local recycling. It is found that the GHG forcing, in general, favor reduced moisture contributions from oceanic sources to the west of the domain in winter and enhanced those from the ones to the east of the domain in both winter and summer for regions in the first category. Under the GHG scenario, moisture contributions from external terrestrial sources are reduced in summer for subdomains in the first category and show a shift from the north to the south for other regions; under the AER scenario, the opposite case can be observed. Local recycling is generally enhanced in summer under both GHG and AER scenarios, with an exception for the regions in the first category, which exhibit reduced local recycling under the GHG forcing.