Civil and Environmental Engineering

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This is the collection for the University of Waterloo's Department of Civil and Environmental Engineering.

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Bioaugmentation coupled with activated carbon for the treatment of petroleum hydrocarbons in groundwater systems
(University of Waterloo, 2024-07-26) Schneider, Adam
The contamination of groundwater by petroleum hydrocarbons (PHCs) is a global concern with negative human health and environmental impacts. The injection of an activated carbon (AC) particulate amendment to create a permeable reactive barrier (PRB) to prevent additional downgradient migration of a dissolved PHC plume from a source area has gained popularity. In this remedial application the selected AC amendment is strategically injected across a dissolved PHC plume and provides sufficient adsorption capacity to remove dissolved PHCs from the groundwater that flows through the PRB. This concentrated mass of PHCs is considered to serve as a haven for indigenous microorganisms to thrive and results in biodegradation of the PHCs and regeneration of the adsorption capacity of the AC. Often anaerobic conditions develop within the PRB which leads to depleted concentrations of electron acceptors. To overcome this limitation, bacterial cultures are co-injected with the AC to increase the rate of biodegradation since some indigenous microorganisms are perhaps not capable, in low abundance or not present to operate effectivity under anaerobic conditions. The overarching objective of this research was to investigate if an AC particulate amendment coupled with bioaugmentation (culture injection) can synergistically enhance the biodegradation of PHCs. The hypothesis postulated was that the combination of powdered AC (PAC) and enriched methanogenic cultures will enhance the biodegradation of benzene, toluene and o-xylene (BTX) under anaerobic conditions. To evaluate this hypothesis, data was collected from microcosm experiments representing static conditions, and from continuous flow column experiments mimicking in situ conditions. Both the microcosm and column experiments were conducted in anaerobic environments and included controls and active treatment systems involving combinations of BTX, PAC, and/or bioaugmentation (BA). The PAC utilized was a virgin coconut-based thermally activated product with a mean particle size of 13.1 μm. The methanogenic cultures were enriched from nature and have been shown to completely degrade benzene (DGG™-B), toluene (DGG™-T), and o-xylene (DGG™-X). The aquifer material used in the experiments was collected from the University of Waterloo Groundwater Research Facility at Canadian Forces Base (CFB) Borden. Five different microcosm systems were constructed using artificial groundwater, aquifer material, methanogenic cultures and PAC. A single-compound experiment used toluene only while a multicompound experiment used BTX. The active systems included microcosms with and without BA and with (A-PAC-BA and A-PAC) and without (A-BA and A) PAC. Control microcosm systems included killed control (autoclaved with biocide), positive control (BA without aquifer material), and starved control (no addition of toluene or BTX). A total of 300 microcosms bottles were assembled and stored on their side in an anerobic glove chamber undistributed except during sampling. Microcosms were sampled at selected timepoints over a period of nearly one year using a repetitive and sacrificial strategy. Dissolved phase samples were used to determine pH, oxidative reductive potential (ORP), dissolved oxygen (DO), BTX concentrations, dissolved inorganic carbon (DIC) content, and sulfate and sulfide concentrations. Gas phase samples collected from the microcosm headspace were analyzed for methane (CH4) and carbon dioxide (CO2). Solid phase samples were also collected to determine bulk BTX concentrations, and deoxyribonucleic acid (DNA) extractions were assayed by quantitative polymerase chain reaction (qPCR). Toluene or BTX mass was replenished as needed in the active systems. There was no evidence of biodegradation in either the killed or starved controls. Depletion of toluene and o-xylene in conjunction with consumption of sulfate and production of methane and carbon dioxide indicated biodegradation occurred in the positive control and all active bioaugmented microcosm systems. In all microcosm systems the depletion of benzene was not observed. As expected, the presence of PAC in the active microcosm systems considerably reduced the aqueous concentrations of toluene or BTX. Bulk toluene or BTX concentration data provided evidence for the regeneration of PAC sorption capacity because of biodegradation. qPCR results support the depletion of toluene and o-xylene in the active bioaugmented systems with elevated populations of key degraders (Desulfosporosinus (DSP) and Peptococcaceae (PEP)). During the final ~30 days, a higher temporal resolution sampling strategy was implemented to collect data to estimate compartmental mass distributions and system biodegradation rates. The estimated biodegradation rate for A and A-PAC microcosms (no BA) were not statistically different at the 5% LOS, as well as the estimated biodegradation rate for A-BA and A-PAC-BA microcosms. Based on the data set assembled from the microcosm experiments, there is no evidence that supports the stated hypothesis. Specifically, the presence of PAC by itself or in combination with BA did not increase the mass of toluene and o-xylene biodegraded or the rate of biodegradation. Five different columns systems were used to examine BTX biodegradation under anaerobic conditions. The active systems included columns with and without BA and with (A-PAC-BA and A-PAC) and without (A-BA and A) PAC. A control column (killed control) containing PAC was constructed from autoclaved materials. The columns were packed with aquifer material and a 6- cm long PAC zone (0.5% by wt) was emplaced in the central part of the column to mimic a PRB for some systems. An access port was used to inject cultures into the PAC zone. Anerobic artificial groundwater augmented with BTX was used as the feed solution. Biocide was added to the feed solution for the killed control column. The columns were run for a one-year acclimation period followed by 9 months of a comprehensive sampling. Dissolved phase samples collected from the influent and effluent were used to determine pH, ORP, DO, DIC content, and BTX, sulfate, CH4, and CO2 concentrations. At the termination of the experiment, solid phase subsamples were collected from each active column and used to determine bulk BTX concentrations, and DNA extractions were assayed by qPCR. There was no evidence of biodegradation in the killed control column. In the absence of BA (A vs A-PAC columns), the PAC zone improved the biodegradation of toluene as supported by the production of CH4 and CO2, and increased population of toluene degraders within the PAC zone. While in both BA systems (A-BA and A-PAC-BA) toluene biodegradation was near complete (>95% mass reduction), suggesting that the PAC zone did not enhance the biodegradation capacity of toluene when combined with BA. Biodegradation of benzene (~25% mass reduction) occurred in the A-PAC-BA system, despite a larger population of benzene degrading microbes in the A-BA system. O-xylene biodegradation was the highest in the A-BA system (~90% mass reduction), which was supported by the DNA results (>107 copies/g o-xylene degraders), along with production of CH4 and CO2. Based on the data set assembled, there is evidence that supports the stated hypothesis. Specifically, the presence of a PAC zone in the column by itself improved the biodegradation of toluene (~95% versus ~70% mass reduction) and o-xylene (~25% versus <20 % mass reduction) compared to the column with no PAC zone. The combination of PAC and BA increased benzene biodegradation (~25% versus <20 % mass reduction) but decreased o-xylene biodegradation (~90% versus ~80% mass reduction) compared to BA but without a PAC zone. Taken together, experimental findings were not able to prove that PAC and BA work synergistically to enhance the biodegradation of BTX. Nevertheless, PAC did not reduce the biodegradation ability of the systems and can therefore still provide benefits when used for groundwater remediation applications. Specifically, the use of PAC in combination with bioaugmentation in field applications may provide benefits by containing the BTX mass in a more spatially confined area for longer durations (> 20 years), which would provide more time for biodegradation to occur.
Biofiltration for Manganese Removal from Groundwater: Mechanistic Insights and Operational Strategies
(University of Waterloo, 2024-06-17) Arora, Hemant
Groundwater is an essential source of drinking water worldwide. Among various contaminants that are present in groundwater, manganese (Mn) is one of them. Manganese in drinking water can cause aesthetic and operational problems and has been associated with cognitive and neurobehavioral effects in children. In response, Health Canada has established as guidelines a maximum acceptable concentration (MAC) of 120 µg/L and an aesthetic objective (AO) of 20 µg/L for Mn in drinking water. Biofiltration provides an environmentally friendly and effective method for removing Mn from water, as it does not require chemicals and does not produce harmful by-products. However, limitations include a prolonged start-up period with virgin media and diminished efficacy at lower water temperatures (< 15°C) due to reduced microbial activity, particularly when iron (Fe) is present as a co-contaminant in groundwater. Additionally, while biofilters are typically operated continuously (24 h/d), intermittent operation (6-12 h/d) in small-scale or remote communities, depending on local demand, may affect the performance of biofilters. Despite research on Mn removal mechanisms by biofiltration, the evolution of these processes as biofilters mature requires further investigation. Consequently, this research aims to deepen the understanding of Mn removal mechanisms in biofilters from startup to maturity and to investigate the influence of filter media characteristics and operational modes (intermittent vs. continuous) on the performance of biofilters for Mn and Fe removal. The research was conducted in three phases, utilizing a combination of pilot-scale biofilters and bench-scale batch experiments. Pilot-scale biofilters were designed and constructed at a drinking water facility in Southern Ontario, Canada and were operated under various configurations for approximately 400 days with raw groundwater containing Mn and Fe. Concurrent bench-scale batch experiments with and without inhibitors were conducted to elucidate different Mn removal mechanisms. This study employed multiple analytical techniques such as scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Raman spectroscopy, adenosine triphosphate (ATP) measurements, extracellular polymeric substance (EPS) analysis, cultural plating techniques, and 16S rRNA gene sequencing. Phase one evaluated the impact of different filter media, including granular activated carbon (GAC), sand, and anthracite, on startup, Mn removal mechanisms, and microbial community dynamics. Findings indicated that filter media characteristics influence the startup period of Mn removal; GAC biofilters primarily initiated Mn removal through adsorption, transitioning to biological and physicochemical processes, while sand and anthracite predominantly engaged in biological processes. The batch tests confirmed these findings, with sand and anthracite media showing biological dominance at the top layer and GAC media exhibiting physicochemical dominance throughout. The presence of manganese-oxidizing bacteria (MnOB) genera varied across biofilter media types and depths, highlighting the complex interplay between biofilter media and microbial colonization patterns. Phase two focused on the evolution of Mn removal mechanisms in a sand biofilter from startup to maturity, utilizing a combination of pilot-scale biofilter and bench-scale batch experiments. The study revealed an initial dominance of biologically generated manganese oxides (Bio-MnOx), which gradually transitioned to physicochemical forms of MnOx. This shift is likely due to the competitive dynamics between MnOx and MnOB, with the influence of MnOB diminishing over time. Other contributing factors include changes in the nutrient consumption patterns of MnOB and shifts in microbial community composition. Several MnOB genera, including Sphingopyxis, Sphingomonas, Hyphomicrobium, Hydrogenophaga, and Variovorax, were present in the biofilter from startup to maturity. Genes associated with direct and indirect biological Mn oxidation pathways were also predicted, highlighting the complex, multi-pathway nature of biological Mn oxidation. Phase three evaluated the performance of intermittently (6 h/d, 12 h/d) and continuously operated biofilters (24 h/d), in addition to the effects of a 10-day shutdown. The findings demonstrated that intermittently operated biofilters maintain Mn and Fe removal efficiency comparable to continuously operated biofilters, although continuous biofilters exhibited higher ATP and EPS levels. Biofilters quickly recovered after a 10-day shutdown, highlighting their robustness. The overall microbial community composition was not significantly different between continuously and intermittently operated biofilters. Overall, the study successfully demonstrated that pilot-scale biofilters could reduce Mn levels below the Health Canada recommended AO of 20 μg/L, achieving over 90% removal efficiency in the presence of Fe at low water temperatures (15°C). The findings highlight the potential of GAC media to shorten start-up times and the feasibility of operating biofilters intermittently without compromising Mn and Fe removal efficiency.
Investigating the impacts of upgrading a full-scale conventional activated sludge process with a hybrid membrane aerated biofilm reactor
(University of Waterloo, 2024-06-06) Lakshminarasimman Meanakshi Sekar, Narasimman
Membrane aerated biofilm reactors (MABR) are an emerging wastewater treatment technology that offer several process advantages such as higher aeration efficiency, simultaneous nitrification and denitrification, and reduced nitrous oxide (N₂O) emission. However, the current knowledge on MABR operations is largely based on bench- and pilot-scale systems that differ in mixing conditions, biofilm thickness control strategies, and cassette arrangement from those employed in full-scale. This study bridged this critical knowledge gap by investigating the long-term performance (20 months) of one of the largest MABR installations in North America and reported the findings on a wide range of responses related to effluent quality, electricity consumption, N₂O emissions, and biofilm characteristics. The key performance metrics related to nitrogen removal, aeration tank operations, and electricity consumption were monitored in a full-scale conventional activated sludge (CAS) before and after upgrading with a hybrid MABR. The inclusion of the hybrid MABR process improved the seasonal nitrification observed in the CAS process before the upgrade to year-round ammonia removal. Denitrification in the hybrid MABR doubled the TN removal in the plant from 30-40% before upgrade to 70-80% afterwards. Operation at reduced MABR airflow (4.5 NL m⁻² hr⁻¹) resulted in lower nitrification rates due to insufficient biofilm thickness control that led to diffusional limitations. Temperature was found to impact nitrification in the MABR with a 22% decrease in nitrification rate from 1.8 ± 0.2 g-N m⁻² d⁻¹ during warm weather to 1.4 ± 0.2 g-N m⁻² d⁻¹ during cold weather conditions. Operation at higher MABR airflow (6 NL m⁻² hr⁻¹) increased the NH₄-N removal efficiency in the aeration tank during cold weather conditions suggesting increased nitrifier seeding due to enhanced sloughing of biofilm into the suspended sludge. The hybrid MABR process achieved high denitrification efficiency (80-97%) throughout the study and was not substantially impacted by ammonia loading, process airflow, or wastewater temperature. Aeration related electricity consumption, as described by volumetric energy intensity (kWh m⁻³), decreased by 50% after the upgrade due to the efficiency of oxygen supply by the MABR and the reduction of aeration requirements downstream aeration basin. Overall, the improved N removal under reduced electricity consumption at full scale demonstrated the potential of MABR as a suitable process intensification technology. Pollutant removal in biofilm processes such as membrane aerated biofilm reactors (MABR) is directly influenced by the biofilm thickness and microbial community functions. However, these biofilm characteristics have not been studied in full-scale MABR systems before. This study addressed this knowledge gap by characterizing the spatial and operational dynamics of key biofilm properties such as thickness, and microbial community structure and functionalities in a full-scale MABR facility. The arrangement of the MABR cassettes in an array along the length of the plug flow MABR train resulted in a longitudinal biofilm thickness gradient. The biofilms on the front cassettes were more than twice as thick as those on cassettes at the back. Examination of biofilm thickness as a function of MABR process airflow indicated that a lower airflow (4.5 NL m⁻² hr⁻¹) resulted in a thicker biofilm (> 1000 µm) throughout the tank. Consistent with the trends in thickness, analysis of Bray-Curtis dissimilarity index showed that there were differences in the biofilm microbial community composition along the length of the MABR tank and between operating phases. Thicker biofilms in the front cassettes of the full-scale tank were predicted to have a higher relative abundance of organisms with anaerobic functions such as fermentation and sulfur reduction and lower relative abundance of organisms with aerobic functions such as aerobic heterotrophy and nitrification. Nitrosomonas was identified to be the main ammonia oxidizer and Nitrospira and Nitrotoga were the main nitrite oxidizers in the biofilm samples. The 16s RNA gene profiles were strongly correlated with biofilm thickness (R² = 0.8) and MABR nitrification rate (R² = 0.4). Phases with thinner biofilm showed higher relative abundance of nitrifiers which corresponded to higher nitrification rates. Thus, optimizing the process airflow to provide adequate biofilm thickness control is key to maximizing nitrification rate in full-scale MABR. Biological nitrogen removal often results in emission of nitrous oxide (N₂O) which is a highly potent greenhouse gas. Current published models for N₂O emissions in MABR have several simplifications that are not representative of full-scale systems. This study developed an improved MABR N₂O model that captured commonly overlooked phenomena such as back diffusion of generated N₂O into MABR lumen gas and the recirculation of the N₂O laden lumen gas for tank mixing and biofilm thickness control. The improved model was validated with measured N₂O concentrations in the lumen gas phase and bulk mixed liquor in a full-scale hybrid MABR facility. The validated model was used to obtain insights into N₂O bioconversion pathways. Model predictions revealed that all N₂O generated in the inner layers of the biofilm, which back diffused into the lumen gas, was via ammonium oxidizing organism activity. The N₂O transported to the outer biofilm layers was reduced via the heterotrophic denitrification pathway. The N₂O gas model predicted that up to 70% of the N₂O carried by the recirculated lumen gas was scrubbed into the mixed liquor which was further denitrified. An N₂O emission factor of 0.18 ± 0.01% N₂O-N/N load was estimated for the full-scale MABR process which removed up to 50% of the influent N load, highlighting the potential of this technology to mitigate N₂O emissions when compared to conventional activated sludge. Release of organic micropollutants (OMP) such as pharmaceuticals and personal care product ingredients in the treated wastewater effluents is concerning as these compounds could have harmful effects in the aquatic ecosystem. This study monitored the removal of 16 OMPs over multiple seasons in a full-scale CAS before and after an upgrade with a hybrid MABR process. A comparison of OMP concentrations in the plant effluent showed that 12 out of 16 target compounds were present at lower concentrations after the upgrade. An examination of plantwide removal efficiencies revealed that highly removable compounds (> 75%) such as acetaminophen, ibuprofen, naproxen, triclosan, triclocarban, and norfluoxetine and the recalcitrant carbamazepine were not impacted by the addition of the MABR process. However, six compounds namely gemfibrozil, sulfamethoxazole, trimethoprim, atorvastatin and its ortho- and para- hydroxy metabolites, that were poorly removed (< 25%) by the CAS configuration had moderate removals (25 to 75%) with the hybrid MABR/CAS configuration. After the MABR upgrade it was found that six OMPs showed higher removal under warm weather conditions (19.3 ± 1.6℃) when compared to cold weather conditions (13 ± 1.2℃). Mass balance analyses on the MABR tank revealed a broad range of compound specific responses such as complete biotransformation (acetaminophen), partial removal (naproxen), and compound formation from unmeasured precursors (sulfamethoxazole, carbamazepine). Overall, long-term monitoring of the full-scale facility before and after the upgrade revealed that upgrading of CAS to a hybrid MABR configuration can enhance the removal of some OMPs that are poorly removed by the CAS process alone.
Evaluation and improvement of robustness in drinking water treatment systems to manage turbidity- and natural organic matter (NOM)-related water quality upsets during extreme weather events
(University of Waterloo, 2024-05-17) Nemani, Kirti Srimani
Climate change poses significant challenges for drinking water treatment plants (DWTPs), with extreme weather events increasingly impacting water quality. While various aspects of climate adaptation, such as source water protection and demand management, are crucial, managing water quality is paramount for consumer safety. Understanding the effects of climate-driven water quality exacerbations on DWTPs is essential, including identifying watershed risk factors and their impact on treatment processes. Quantifying and substantiating a treatment system's capability and vulnerability to different raw water quality scenarios, especially for turbidity and Natural Organic Matter (NOM) is crucial for performance assessment and preparing for future extreme weather events. In this context, enhancing robustness, which is the ability of a DWTP to maintain desired drinking water quality even during raw water quality disturbances, is key to safeguarding treatment processes against sudden and long-term changes in surface water quality. However, existing tools for assessing vulnerabilities and improving resilience in critical infrastructure lack a focus on water quality management and specifically on evaluating and enhancing treatment process robustness. A comprehensive framework is needed to guide utilities in determining the robustness of their systems and devising strategies to address deficiencies. There is also a need for robustness metrics specifically addressing NOM reduction/removal which is still an unexplored area. This thesis contributes to understanding climate impacts on drinking water treatment processes, focusing on two critical water quality parameters (WQPs) - turbidity and NOM. It explores the implications of turbidity and NOM variations on treatment processes within the context of watershed changes due to climate change. Additionally, this thesis examines the robustness of DWTPs as a vital climate adaptation strategy, synthesizing related concepts like resilience, reliability, risk, and vulnerability to present a comprehensive understanding within the context of DWTPs. The most significant contribution of this research is the development and introduction of three robustness frameworks tailored to DWTPs. The general framework outlines systematic steps for assessing and improving overall robustness, while the parameter-specific framework applies this methodology to specific water quality parameters (WQPs). A plant-specific framework then tailors the parameter-specific approach to individual DWTPs. The thesis proposes a parameter-specific framework for turbidity, utilizing the turbidity robustness index (TRI) for evaluation of individual treatment processes and the overall robustness index (ORI) for the overall assessment of the plant. This framework is applied to two full-scale DWTPs, Plants A and B in Ontario, Canada, using historical plant data and bench-scale experimental data simulating extreme high-turbidity scenarios. The application identifies less robust processes vulnerable to climate extremes, operational responses for short-term robustness, and critical WQP thresholds necessitating capital improvements. This framework serves as a valuable tool for assessing and enhancing the robustness of DWTPs, offering insights into their current state, and aiding in climate adaptation planning. Another notable contribution of this research lies in the comparative analysis of outcomes from four DWTPs where the turbidity robustness framework was implemented. This comparison not only underscores the versatility of the framework, but also offers valuable insights into the performance of four distinct plants using standardized metrics. It also introduces a decision-tree for charting out the next steps for utilities based on the robustness assessment and shows examples tailored to each plant, enhancing the practical applicability of the framework. This thesis also addresses the lack of NOM-related robustness metrics and introduces a novel index, Organic Matter Robustness Index (OMRI) to quantify the robustness of critical treatment processes. This index aims to incorporate the complexity of NOM in natural waters and the variety of surrogate parameters used for measurement at DWTPs in the NOM robustness quantification. Apart from the OMRI, this research also proposes another quantitative method for evaluating NOM robustness by extending the use of TRI to appropriate NOM surrogate parameters. This index was incorporated in the NOM robustness framework, which was applied to plant B, with a focus on historical plant data as well as experimental data simulating extremely high NOM scenarios. Short-term adaptation options in the form of operational changes were identified to improve the removal of NOM in such adverse source water situations. The results from this study show the applicability and ease of use of the OMRI to a full-scale DWTP and offer insights into the current operational robustness with respect to NOM of plant B.
Enhancing Real-Time Data Acquisition from Embedded Road Structural Health Monitoring Systems
(University of Waterloo, 2024-04-23) Ceric, Matea
Canada's economy heavily relies on its roadways, yet managing pavement assets faces challenges due to past infrastructure spending cuts. Addressing this, a pavement management system (PMS) is essential for efficient resource allocation. Traditional surface condition monitoring within PMS is time-consuming and costly. In response, in situ condition monitoring, integrating AI and ML, emerges as a viable alternative, aligning with the development of "smart" pavements. This thesis, part of the Smart Pavements project at the University of Waterloo, assesses an instrumented pavement section on Courtland Avenue, Kitchener. It provides a comprehensive assessment of the implementation, data collection, data analysis and database concept development processes of an instrumented test section. It integrates advanced monitoring technologies and predictive modeling, yielding promising results. Identified gaps in the literature are addressed, with scalability and cost-benefit analysis highlighted for future research. Challenges in instrumentation and testing, including weather delays, are discussed, with recommendations provided. Material testing procedures and truck testing results are outlined, emphasizing seasonal variations and the impact of vehicle wander on pavement behavior. Software comparisons and detailed trend analysis reveal insights into pavement performance. Additionally, a basic database framework is proposed for efficient data management. This study contributes to understanding pavement instrumentation, long-term behavior, and the efficacy of simulation methods. Recommendations for future work include AI/ML integration, long-term data collection, database development, and standardized guidelines for sensor implementation, aiming to enhance pavement management practices nationwide.
Effects of Prolonged Shutdown on the Performance and Microbial Activity of Intermittently Operated Biofilters for Manganese Removal from Groundwater: Pilot Scale Study
(University of Waterloo, 2024-04-18) Zore, Ujwal
Apart from aesthetic concerns, manganese (Mn) in drinking water has been associated with cognitive and neurobehavioral effects in children. Recently Health Canada has changed its drinking water guidelines for Mn from an aesthetic parameter to a regulated parameter with a maximum acceptable concentration (MAC) of 120 μg/L, an aesthetic objective (AO) of 20 μg/L, and a treatment objective limit of 15 μg/L. While biofiltration has proved to be an effective treatment option for Mn and iron (Fe), it is not widely used in North America. Also, in small-scale communities, treatment plants often adopt intermittent operation schemes, wherein, water treatment occurs for a few hours per day, based on demand. Among the various operational aspects that could potentially affect the performance of intermittently operated biofilters, prolonged filter shutdown remains a critical concern. However, limited insights exist regarding both the intermittent operation for Mn and Fe removal from groundwater and the impact of a prolonged shutdown. This study aimed to fill these knowledge gaps by comparing the performance of intermittently and continuously operated biofilters for Mn and Fe removal from groundwater, and by investigating the impact or a prolonged shutdown of these filters. To achieve these objectives, three pilot-scale biofilters were located at a drinking water treatment facility in Southern Ontario, Canada, out of which two biofilters were operated continuously and one intermittently (6 h per day). The biofilters were initially operated for a couple of months, then underwent a six-month shutdown period, and then resumed active operation for three months. Sand was used as the biofilter media providing an empty bed contact time (EBCT) of 15.6 minutes. Raw groundwater containing Mn (31 μg/L) and Fe (96 μg/L) was fed to the biofilters and the effluent flow rate was maintained at 5 m/h. Mn and Fe removal was assessed before and after the extended shutdown in order to gauge its impact on biofilter performance. In addition, turbidity, pH, DO, oxidation-reduction potential (ORP) and total organic carbon (TOC), were periodically monitored. Microbiological changes were analyzed using AxP (adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP)) and other microbiological analyses. Lastly, the storage strategy (SS) utilized during an extended shutdown period might play a crucial role, therefore four different storage strategies were investigated. To briefly summarize the results, during the start-up phase, after 56 days, all biofilters achieved Mn removal to below 15 μg/L, with the intermittently operated biofilter exhibiting lower removal rates and not reaching a steady state, while Fe removal reached a steady state within a week for all biofilters. Next, during the six-month extended shutdown, a notable reduction in ATP occurred, but all biofilters seemed to have remained viable for 4 months, potentially due to the SS utilized. Also, it was found that manganese oxidizing bacteria (MnOB) were able to persist and actively oxidize Mn even after the six-month-long shutdown. Lastly, post-extended shutdown all biofilters approached the previous Mn removal rates within 20 days of restart and then reached a steady state within a month of operation. Notably, intermittently operated biofilter performed equally well as continuously operated biofilters. Also, Fe removal was not found to be affected by the extended shutdown. This suggests that the biofilters were able to quickly regain their performance even after a six-month extended shutdown highlighting the resilient nature of these biofilter systems. Overall, this study enhances the understanding of Mn removal in intermittently operated biofilters, and suggests ways to mitigate the effects of prolonged shutdowns, thereby expanding the applicability of these biofilters, especially to smaller communities.
Achieving contrapuntal balance at a lake outlet: Restoring salmon spawning habitat with gravel augmentation design
(University of Waterloo, 2024-04-09) Iun, Megan
The degradation of gravel bed rivers in logging and climate-impacted watersheds has led to an increase in salmonid habitat conservation and restoration efforts. Gravel augmentation is one such technique that seeks to restore altered aquatic habitat and sediment transport dynamics in sediment-starved streams by placing gravel pads in the river. The pads act as a sediment source that can be reworked by flow or fauna to suit their ecological needs, thereby allowing the river to “heal” itself without imposing static structural designs on a natural environment. Common points of failure for these projects include: (1) the immediate scour of the gravel pad which can wipe out buried eggs, (2) the infilling of the gravel interstices with fine particles which can limit oxygenated hyporheic flow and choke the buried eggs, and (3) low utilization by the target species due to unsuitable hydraulic conditions for spawning. The risk of the first two hazards can be limited by designing the gravel placements at downstream of lakes, as the upstream lake can buffer peak flows to its outlet stream and trap fine sediment. Much like composing counterpoint in music, a delicate balance is needed between multiple engineering criteria to identify the optimal area along the accelerating channel length where most criteria are fulfilled. Despite this understanding and the common use of lake outlets for these projects in industry, there are few design guidelines tailored for these environments. This project evaluates the design criteria of a gravel augmentation project for salmon spawning habitat restoration at a lake outlet. A calibrated two-dimensional (2D) hydrodynamic model was developed using TELEMAC-2D. The sediment transport predictions from the model were verified by tracking tracer stones equipped with Radio Frequency Identification (RFID) after one year. The model results were used to identify optimal placement areas. The 2D model was found to adequately capture the measured depth-averaged velocities when set with appropriate boundary conditions and calibrated with the roughness coefficient. However, the roughness-dependent shear velocity calculation in the model formulation results in a direct dependency of the model outputs on the sole calibration parameter. This relationship is highly sensitive and creates modeling artefacts when using roughness zones to calibrate the model. The tracer results indicate that the model appears to overpredict sediment transport due to the limitations of the deterministic approach of assessing grain mobility, which is inherently a stochastic process. Although there is likely error associated incorrect assumptions on critical mobility thresholds and representative grain sizes, the relative lack of tracer mobility during the study year limits the current ability to revise these assumptions. Nevertheless, the results show that the application of 2D hydrodynamic models to sediment transport predictions should be approached with caution and should be accompanied by field validation to ensure confidence in the model conclusions. Using the model as is, the optimization analysis results suggest that designing to prioritize longevity may require compromising the other design criteria. Conversely, optimizing the design to minimize the risk of fines infilling severely limits the available placement areas. Prioritizing stability may decrease the likelihood of immediate utilization but may be required due to the uncertain availability of funding for re-injecting gravel after the initial construction.
Study of Performance of Geosynthetic-Reinforced Pavements by Full-Scale Field Study, Laboratory Testing, and Numerical Modelling
(University of Waterloo, 2024-03-19) Wang, Danrong
This study provides a comprehensive understanding of geosynthetic-reinforced pavements from different perspectives including small-scale laboratory testing, a full-scale field study, and numerical simulation. This study on geosynthetic-reinforced pavements evaluated two geosynthetic materials: fibreglass geogrid in the asphalt layer; and geogrid composite at the interface of base and subgrade. Fibreglass geogrid-embedded asphalt samples were made with three types of fibreglass geogrids – Geogrid 11, Geogrid 11 EPM (Engineered Polymeric Membrane) and Geogrid 10. The samples were tested with a conventional Hamburg Wheel-Tracking Test (HWTT) in a small-scale laboratory facility to evaluate the rutting and moisture susceptibility. The test outcomes indicate that Geogrid 11, characterized by larger openings, exhibits superior resistance to rutting. Conversely, Geogrid 10, with smaller openings, demonstrates lower susceptibility to moisture. Geogrid 11 EPM, featuring an additional adhesive membrane, exhibits the poorest performance in terms of both rutting resistance and moisture susceptibility. This suboptimal performance is attributed to the insufficient compaction effort, which further initiated another test proposed to evaluate the rutting resistance, namely the dynamic creep test. The proposed test was built upon the existing flow number test, with the stressed importance of extended testing protocols. The test results were analyzed with three major indicators, flow number, mean creep rate, and ultimate creep modulus, which highlight that fibreglass geogrid reinforcement plays a crucial role in enhancing resistance to permanent deformation, thereby increasing the asphalt's resistance to rutting. Results demonstrate a contrary conclusion with the HWTT, that Geogrid 11 EPM with larger openings but extra bonding provides the best rutting resistance. A less aggressive freeze-thaw (F-T) conditioning procedure was introduced to integrate with the dynamic creep test for geogrid-embedded asphalt samples to assess the impact of moisture damage on permanent deformation. The findings reveal that unreinforced samples consistently exhibit the poorest performance. In contrast, geogrids with larger openings and additional bonding demonstrate a capacity to mitigate the detrimental effects of moisture-induced damage. The feasibility, constructability, and impacts of construction activities on pavements reinforced by these two types of materials were assessed during the construction of the field trial sections, and evaluated against an unreinforced control section. Post-construction field performance was monitored by field testing and instrumentation. Pavement stiffness tested by the Light Weight Deflectometer in the control section was notably influenced by ambient and pavement temperatures, indicating the effect of geosynthetic materials in preventing pavement stiffness from varying from temperature changes. Roughness measurements underline the need for an overlay of the surface course with geogrid reinforcement in the asphalt concrete layer. Truck testing further demonstrates the load-distribution capabilities facilitated by the fibreglass geogrid embedded in the asphalt layer. Field instrumentation was monitored for a year after construction completion, which demonstrates negative temperature differentials in the geogrid composite section during winter, indicating the effectiveness of the geogrid composite in regulating subgrade temperature and mitigating frost-related risks. Moisture data further illustrates relatively drier conditions in the geogrid composite section, underscoring its draining behaviour, particularly pronounced during thawing seasons. In the fibreglass geogrid section, a lower level of strain variation and pressure experienced at the bottom of the asphalt highlights the reinforcement capabilities and strain-absorption properties facilitated by the fibreglass geogrid. Additionally, the geogrid composite section exhibits lower strain and pressure on the subgrade compared to the control section, highlighting the reinforcing impact of the geogrid composite on the subgrade. Lastly, pavement layer temperature predictive models with the input of ambient temperature were developed. A numerical model coupled with thermal-hydro-mechanical processes was created to simulate the pavement performance under freeze-thaw actions and examine the use of geogrid composite on the subgrade. The simulation from 2022 to 2023 using the developed model, with the input of pavement layer temperature predictive models and characterized field material properties, demonstrates less temperature variation in the subgrade, lower saturation levels, and reduced displacement after the thawing period in the geogrid composite section compared to the control section. This highlights the crucial role of the geogrid composite in drainage, subgrade temperature stabilization, and mitigating freeze-thaw disturbances in the pavement.
Natural Language Processing using Deep Learning for Classifying Water Infrastructure Procurement Records and Calculating Unit Costs
(University of Waterloo, 2024-03-06) Khaki, Milad
This thesis introduces a novel ontology-based deep learning classification model specifically tailored for civil engineering applications, focusing on automating the extraction and classification of water infrastructure capital works tenders and progress certificates. Utilizing ontology for standardizing tender-bid data and employing Named Entity Recognition (NERC) for item categorization, the model adeptly addresses the challenges posed by the diversity in document styles and formats. Incorporating Long Short-Term Memory (LSTM) structures within the model enables the learning of both linear and non-linear dependencies between words. This aspect is particularly significant in tackling the unique language constructs present in tender-bid document records. The model's effectiveness is underscored by its impressive classification accuracy, achieving 92.6% for testing data and 98.7% for training data, thereby marking a significant advancement in the field. The practical application of this model through a web server highlights its adaptability and efficiency in real-world scenarios. The model's role in tasks such as unit cost calculation establishes a new benchmark in the industry, showcasing the thesis's innovative contributions in areas like ontology-based data structuring and LSTM-driven automated unit cost computation. Looking beyond its current scope, this research holds potential for broader applications and adaptations in different civil engineering domains. It lays the groundwork for future enhancements, including exploring multilingual extensions and specialized approaches aligned with evolving industry trends. This thesis amalgamates data preprocessing, deep learning, and engineering expertise to boost efficiency and accuracy significantly. The unique methodology fosters continuous improvement and broad applicability across different regions. The practical integration of this technology in civil engineering tasks, demonstrated through the web server, opens avenues for further development to encompass a wider array of applications. Future research directions include refining the framework to cater to the dynamic needs of various civil engineering domains and extending the web server's capabilities for real-time data processing and analysis. Investigating the applicability of this methodology in other engineering or interdisciplinary contexts could also provide valuable insights, extending the utility of this research. This thesis lays a solid foundation for ongoing enhancements in capital work planning and tender contract assessment within the civil engineering industry.
Enabling Human-Machine Collaborative Inspections through Smart Infrastructure Metaverse
(University of Waterloo, 2024-02-08) Al-Sabbag, Zaid
Over the last ten years, novel Artificial Intelligence (AI) based structure assessment methods and tools have been proposed to identify and quantify structural damage indicators (e.g., cracking, spalling, corrosion, etc.) from visual data (e.g., images, LiDAR). However, despite an urgent need for such technology in managing infrastructure, widespread adoption of these technologies in the field has been quite limited. One of the main obstacles is the lack of real-time communication and interaction between the human inspectors, on- and off-site, and the technologies being deployed to support data collection, processing, and decision-making. This thesis focuses on enabling real-time remote collaborative structural inspections by integrating on-site inspectors, remote experts (e.g., engineers, stakeholders, etc.) responsible for making critical decisions, advanced data collection platforms (e.g., ground robots, drones, etc.), and AI algorithms that can rapidly interpret data, into an automated inspection system that supports human-machine collaboration. The motivation is to solve the technical and scientific challenges that prevent real-time collaboration between human users (on-site inspectors, remote experts) and machine agents (robots, AI). This thesis proposes a system called the Smart Infrastructure Metaverse (SIM) to enable human users and machine agents to collaborate in real-time by utilizing Mixed Reality (MR) and Virtual Reality (VR) headsets which enable humans to interact with each other and with machine agents remotely in an immersive environment. The SIM system integrates robotic data collection platforms to collect visual data of the site, with critical guidance from human users on how to collect the best data. The data is then analyzed in real-time by AI computer vision algorithms that utilize input from the human users to localize and quantify structural damage. The on-site inspectors and remote experts are then able to collaborate on reviewing the results in a spatially aware context through an immersive environment supported by MR/VR technology, and can utilize machine agents to collect more data from the site and/or re-analyze previous data based on the human users' expert judgement. Several scientific challenges are addressed in this thesis as part of the process of creating SIM. Each challenge deals with facilitating collaboration between human users and machine agents for a different component of the SIM system. First, input from the on-site inspector must be incorporated into the data analysis step to minimize the gap between data analysis and verification by humans and ensure the high quality of results. The approach is to utilize human-AI collaboration for quantifying the sizes of structural damage regions. This is accomplished by integrating an AI-based interactive image segmentation algorithm with the MR headset which allows for refining the segmentation results interactively through user feedback. Second, accurate spatial alignment between separated devices with heterogeneous sensing and processing capabilities (e.g., MR headsets, robots) is still an open problem that is critical for spatially-aware human-robot collaboration. The approach utilized was to develop an image-based localization algorithm to spatially align the MR headset and robot in real-time, which facilitates human-robot collaboration to enhance the reliability of the data collection process by engaging the MR-equipped human inspector with the data collection platform. Third, seamless integration of VR users into SIM is required for distributed collaboration between remote VR users and on-site MR users. This includes solving the technical challenges related to spatial alignment between VR and MR users, as well as how VR users can interact with other components of SIM such as robots and AI. The approach is to utilize panoramic images to allow VR users to remotely inspect the site, and a novel image-based localization algorithm was developed to spatially align panoramic images with their real locations on-site. Distributed collaboration also includes integrating all of these components into a unified system as part of SIM, with the goal of enabling on-site and remote inspectors to collaborate with each other and with robots and AI through MR/VR. Experimental results are presented for evaluating each component of SIM individually, including lab and field results for evaluating the accuracy of the proposed systems for MR/VR and robotic implementations.
Valuation of in-situ Building Materials for Resource Recovery
(University of Waterloo, 2024-02-08) Mollaei, Aida
The construction industry is among the largest contributors to global raw material consumption and is responsible for 40% of annual greenhouse gas emissions. Recovery of building materials at the end of a building's life, often seen as a common circular approach, can help mitigate the environmental impacts within this sector. However, the feasibility of recovering in-situ building materials is dependent on various technical, operational, financial, environmental, and regulatory factors, making the implementation of resource recovery complex and challenging. The main objective of this research is to develop methodologies that improve the recovery of building materials at end-of-life through assessment of the value of in-situ building materials. At the core of this research, a decision support tool is developed that incorporates the main factors that impact the value of materials embedded in buildings. The tool is designed based on a multi-objective optimization model that estimates optimal end-of-life options for building components. Throughout this research, the tool is applied to various case studies and analyzed through sensitivity analyses. Using the developed tool, a novel methodology is proposed to assess the efficacy of policies focused on deconstruction and building recovery. Following that, the impact of regional factors such as labour costs, material markets, and socioeconomic factors, are assessed on building end-of-life strategies. The findings underscore the necessity of tailored policies and regulations to effectively reduce waste generation within specific regional contexts. Finally, expanding the applicability of the developed tool on future building stocks, a methodology aimed at evaluating circular design and construction strategies on the recovery potential of buildings is provided. This thesis contributes to the development of optimized material recovery processes that result in waste reduction and carbon emission mitigation. Realizing the recovery potential of building materials is a pivotal step towards fostering a more circular construction sector.
Conventional and Oxidant-amended Biofiltration to Improve Treatment Resilience in Drinking Water Systems Vulnerable to Wildfire
(University of Waterloo, 2024-01-26) McGregor, Lauren
Climate-change-exacerbated landscape disturbances can create obstacles for the provision of safe drinking water. The threats posed by wildfires are of particular concern due not only to the potentially extreme nature of their effects, but also because millions of people worldwide depend on water sourced from forested watersheds. Wildfire may lead to major shifts in the concentration and character of dissolved organic carbon (DOC), which may impair drinking water treatment processes to the point of causing service disruptions or outages. Resource-limited small systems can be especially vulnerable to variable water quality, underscoring a need for wildfire-resilient treatment strategies that are cost-effective and less operationally demanding than conventional processes. Biofiltration technologies—especially slow sand filtration—have been proposed as sustainable, low-cost strategies to remove DOC; however, their effectiveness has not been thoroughly investigated during periods of extreme source water quality change such as the episodic deteriorations possible following severe wildfire. Despite the operational simplicity of biofiltration, it is often described as a “black box” process due to our limited knowledge of its biological treatment mechanisms. A better understanding of biofiltration response to wildfire-associated source water disturbances at both the treatment performance and microbial community levels may increase the adaptability of biofiltration processes to climate change effects. Furthermore, biofiltration enhancement is an emerging area of research focused on the customization of biofiltration processes through exerting greater control at the design, process, and influent stream levels. Potential benefits include increased biodegradation of organics and lower incidences of hydraulic challenges. For many of these strategies, there has been little investigation in slow sand filtration. This work aims to advance knowledge in these areas through the execution of two main objectives: 1) assess DOC removal capacity in conventional and peroxide-amended biological sand filters when treating wildfire-ash-impacted water at bench-scale, and 2) evaluate the impacts of wildfire-associated disturbances and peroxide exposure on biofilter bacterial communities. Challenge testing with severely wildfire-ash-impacted water was conducted on biofilters operated in duplicate under conditions closely resembling slow sand filtration. Filters were subjected to two-, four-, and seven-day disturbance periods, each followed by a five-day return to “baseline” source water quality. One of these pairs, as well as another pair not undergoing ash challenge testing, received intermittent low-dose hydrogen peroxide amendment. Effluent DOC concentrations were elevated, and DOC removal declined during challenge periods; however, DOC characterization analysis showed this was likely the result of a higher proportion of slowly biodegradable humic and aromatic organic matter in the ash-impacted water. No significant evidence of impairment to biodegradation was observed. Biofilter performance was consistent within each disturbance period and recovered within hours of the return to baseline conditions. Over the 30-day experimental phase, the impacts of hydrogen peroxide amendment on organic matter accumulation and DOC removal were not significant to practice. Amplicon sequencing was carried out on filter media samples collected throughout the experimental phase. Community composition and diversity were compared across experimental conditions and were assessed alongside biofilter performance to identify potential connections. DNA sequencing was also conducted on media samples collected from a similar set of biological sand filters in a previous ash challenge experiment, which used a distinctly different source water. The lack of compositional differences between microbial communities in filters under different experimental conditions supported the assertion that ash-impacted water and peroxide amendment did not severely disrupt the biological communities in the long-term. Comparison of the two filter sets, however, demonstrated the significant impact of source water character on biological filter community characteristics and dynamics. Collectively, the two components of this work provided process insights into biofilter disturbance response and resilience from multiple perspectives.
Towards a Better Understanding of Activated Carbon-Based Amendments for In Situ Treatment of Petroleum Hydrocarbons in Anaerobic Groundwater Systems
(University of Waterloo, 2024-01-11) Marrocco, Andrea
Injected activated carbon (AC) particulate amendments for the in situ treatment of groundwater impacted by petroleum hydrocarbons (PHCs) is relatively new, and relies on a combination of AC sorption and biodegradation. Currently the performance of this technology remains unclear, primarily related to the long-term interplay between sorption and biodegradation and whether the presence of AC enhances the anaerobic biodegradation of PHCs. To address these uncertainties, this research investigated the sorption and anaerobic biodegradation (sulfate reducing and methanogenic) behaviour in microcosm experiments amended with AC and column experiments designed to mimic an AC permeable reactive barrier (PRB) over a period of 1 to 2 years. The powdered AC (PAC) used in this research (WPC from Calgon Carbon Corporation) had a rough, irregular surface with potential macropore openings of 0.8 ± 0.3 µm, and variable particle sizes with an average diameter of 11.5 ± 4.4 µm. Sorption and desorption equilibrium experiments showed that the magnitude of single-solute (benzene [B], toluene [T], or o-xylene [X]) and multi-solute (BTX combined) sorption or desorption followed X > T > B and B > T > X, respectively. Due to competitive sorption, the magnitude of B, T, and X sorption in the multi-solute system was reduced relative to the single-solute systems. Sorption and desorption equilibrium conditions differed suggestive of hysteresis; however, this behaviour was not fully explored in this research. The best-fit single-solute Freundlich isotherm parameters for benzene, toluene and o-xylene were 36.1 ± 3.8, 0.484 ± 0.045, and 88.2 ± 7.7 for K_(f_i ) ([mg/g][L/mg]n) and 0.421 ± 0.044, 132 ± 20 and 0.371 ± 0.099 for n_(f_i ) (-), respectively. The improved simplified ideal adsorption solution (ISIAS) model was fit to the multi-solute sorption data and the competition factors (ai) were estimated for benzene, toluene and o-xylene as 1.42 ± 0.38, 1.43 ± 0.16 and 1.08 ± 0.08, respectively. Temporal sorption (up to 48 hours) and desorption (up to 720 hours) experiments showed that the time to reach sorption or desorption equilibrium for single-solute benzene and toluene was rapid (≤ 0.5 hours). Single-solute (toluene-only) and multi-solute (BTX) abiotic and bioactive (including sulfate-limited [10-20 mg/L SO42-]) or sulfate amended [138-275 mg/L SO42-]) microcosms with and without PAC were constructed (in addition to starved controls without toluene, BTX or PAC). Aqueous and solid phase toluene or BTX concentrations from the single- and multi-solute PAC amended microcosms, respectively, were compared to the single- and multi-solute Freundlich or ISIAS model predictions. In general, both the single- and multi-solute sorption isotherm models were found to overestimate the measured solid phase concentrations in the microcosms. This disparity is presumably due to differences in mixing conditions and solution matrix chemistry, or competitive sorption by metabolites and biofilm formation in the PAC amended microcosms. In the multi-solute microcosm systems, the observed o-xylene solid phase concentrations deviated the most from the ISIAS model predicted solid concentrations followed by toluene and then benzene. In the subset of single- and multi-solute sulfate-limited bioactive microcosms, evidence of methanogenesis coupled to a background substrate (other than toluene or BTX) was evident from the geochemical (i.e., CH4 production) and molecular (i.e., Methanomethylovorans, Methanosaeta and Methanobacterium enrichment) data. Methane production and methanogenic enrichment were consistently elevated in the bioactive microcosms with PAC, potentially supporting enhanced methanogenesis and archaeal growth in the presence of AC. Contrarily, in the subset of single- and multi-solute sulfate-amended bioactive microcosms, sulfate reduction was coupled to the oxidation of toluene or o-xylene (not benzene, which was recalcitrant) evidenced by the repetitive or preferential biodegradation of toluene followed by o-xylene in the multi-solute microcosm and supported by geochemical (i.e., SO42- reduction, and HS- and total inorganic carbon [TIC] formation) and molecular (i.e., enrichment of sulfate reducing bacteria, including Desulfosporosinus, Desulfoprunum and Desulfobacteraceae) data. In the single- and multi-solute sulfate-amended bioactive microcosms with PAC, the solid phase mass of toluene was repetitively reduced by ≥ 96% showing that PAC regeneration occurred during anaerobic biodegradation. Although anaerobic biodegradation of toluene and o-xylene were repetitively demonstrated, there was no substantial difference in the PHC, geochemical or molecular data collected between the single- or multi-solute sulfate amended bioactive microcosms with and without PAC indicating that the presence of PAC did not influence the anaerobic microbial activity. Additionally, the anaerobic biodegradation rate of toluene was not enhanced in the presence of PAC. Collectively, there were no discernible differences in the anaerobic biodegradation of toluene between the sulfate amended bioactive microcosms with and without PAC over the 1-year monitoring period. Three types of single-solute (toluene-only) and multi-solute (BTX) columns (37 cm long, 3.75 cm inner diameter) were constructed to represent PAC sorption alone, bioactivity alone, and PAC sorption with bioactivity. The columns were operated for approximately 2 years, with Year-1 serving as an acclimation period, and Year-2 used for high-resolution temporal monitoring. For the columns containing PAC, a 6-cm long PAC zone (0.5% wt/wt) was located near the middle of the column to mimic an AC PRB. During Year-2 for the multi-solute column with PAC sorption alone, the change in BTX concentration between the influent and effluent followed X > T > B given that o-xylene has the highest sorption capacity followed by toluene and then benzene. For the single-solute and multi-solute columns with PAC sorption alone the change in toluene concentration between the influent and effluent was greater for the single-solute column relative to the multi-solute column given that the sorption capacity of toluene was reduced in the multi-solute competitive system. For the multi-solute bioactive column without PAC sorption the change in concentration between the influent and effluent followed T > X > B due to the preferential biodegradation of toluene prior to o-xylene and the recalcitrance of benzene (as observed in the microcosm experiments). For the multi-solute bioactive column with PAC sorption the change in concentration between the influent and effluent followed T > X > B due to the preferential biodegradation of toluene and preferential sorption of o-xylene as toluene was biodegraded. The solid phase concentration of toluene within the PAC zone of the single- and multi-solute bioactive columns was highest at the leading edge followed by a gradual reduction towards the end of the PAC zone. The gradient in the solid phase toluene concentration shows that toluene desorbed more due to biodegradation towards the end of the PAC zone, furthest from the influent where toluene was continually replenished. In the bioactive multi-solute column, the magnitude of solid phase BTX concentrations within the PAC zone followed X > T > B at the leading edge; however, directly downgradient the solid phase BTX concentrations within the PAC zone followed X > B > T due to the biodegradation of toluene which resulted in higher sorption of o-xylene and benzene. Using the Year-2 data, an overall column mass balance was estimated by subtracting the cumulative effluent mass from the cumulative mass injected. The single- and multi-solute bioactive columns with PAC sorption yielded the largest removal of toluene mass compared to columns with either only PAC sorption or only bioactivity. For example, among the single-solute columns the mass removal of toluene was greatest for the bioactive column with PAC sorption (99.5% reduction), followed by the column with only PAC sorption (74.6% reduction) and the column with only bioactivity (44.4% reduction). The depletion in effluent toluene mass during Year-2 was consistent between the single- and multi-solute bioactive columns with PAC sorption; however, for the multi-solute column breakthrough of benzene and o-xylene occurred given the recalcitrance of benzene and the competitive inhibition of o-xylene during toluene biodegradation. Anaerobic biodegradation within the single- and multi-solute bioactive columns with or without PAC sorption was supported by changes in geochemical parameters that would be expected under sulfate reducing and methanogenic conditions (i.e., SO42- reduction, and HS-, TIC and CH4 formation). Like the microcosm systems, there was no difference in the magnitude of change of the geochemical parameters between columns with or without PAC, suggesting that the PAC zone in the bioactive columns did not influence the microbial activity. However, the PAC zone did influence the spatial distribution of anaerobic microbes. For the columns with only bioactivity the relative abundance of Methanosarcina and Methanomethylovorans were highest at the influent ends relative to the effluent ends. Whereas, for the bioactive columns with PAC sorption the relative abundance of Methanosaeta, Methanobacterium and Methanosarcina were highest within the PAC zone relative to outside of the PAC zone, in addition to being higher in abundance relative to all bacteria detected within the PAC zone (primarily Desulfosporosinus, Edwardsbacteria and Berkelbacteria). In the multi-solute bioactive column with PAC sorption, the abundance of Desulfosporosinus was also notably elevated at the leading edge of the PAC zones (coinciding with the location of the highest solid phase toluene concentration sorbed to the PAC). Compound specific isotope analysis (CSIA) revealed enrichment of 2H-T in the single- and multi-solute columns with only bioactivity or PAC sorption, although the average value of δ2H-T between the single- and multi-solute columns with only bioactivity was 36.1 ± 8‰ greater than the columns with only PAC sorption, as expected. The magnitude of hydrogen isotope fractionation of toluene associated with a combination of PAC sorption and biodegradation is unknown given toluene was depleted in the bioactive column with PAC sorption. Unlike toluene, a direct comparison of the hydrogen isotope fractionation of o-xylene between the multi-solute columns showed that the average value of δ2H-X was 54‰ and 58‰ greater in the bioactive column with PAC sorption relative to the columns with only PAC sorption or only bioactivity, respectively. 2H-X enrichment in the multi-solute bioactive column with PAC sorption was presumably due to a significant amount of o-xylene sorption to the PAC as toluene was biodegraded as opposed to substantial o-xylene biodegradation (supported by the solid phase data). Collectively the compiled data sets provide comprehensive insight into how AC particulate amendments behave in anaerobic systems in contact with PHCs, and the interplay between BTX sorption and anaerobic biodegradation under sulfate reducing and methanogenic conditions. These data provide direct evidence that the presence of PAC particulate amendments does not enhance the biodegradation of BTX relative to systems with no PAC under sulfate reducing conditions. Instead, the presence of the PAC provides rapid reductions in contaminant concentrations relative to systems without PAC and sustains reductions in the aqueous phase concentration of the most preferentially degraded solute under variable loading conditions as the PAC is regenerated. The PAC also influences microbial activity during PHC biodegradation by promoting microbial growth on the PAC, with notably high methanogenic enrichment. This research also provides evidence that ideal isotherms are not representative of the sorption behaviour in bioactive systems with AC and tend to overestimate sorption. Finally, PAC sorption, most notably for the most preferentially sorbed solute in the multi-solute system, generates substantial hydrogen isotope enrichment which may lead to overestimations in the fractionation presumed to be associated with biodegradation when integrating CSIA into monitoring approaches for bioactive systems with AC.
A river's connective tissue: Lab observations of particle pathways and riffle formation during floods
(University of Waterloo, 2024-01-05) Mueller, Lukas
In rivers it is difficult to quantify bedform dynamics during storm events. Direct observation of sediment pathways would provide insight into the mechanisms that underly bedform formation and destruction. In the current study, our objective was to visualize these processes in a meandering pool riffle system with partial bed cover. Observing erosive and depositional patterns, as well as the locations of active sediment transport, provides insight into the validity of various pool-riffle maintenance theories. We used a physical 1:40 scaled model of Toronto’s Wilket Creek to simulate storm events during which riffles formed as connective bedforms between alternate point bars. Exported sediment was weighed and sieved to measure the grain size distribution, while the bed’s pre- and post- storm topography was quantified using Structure-from-Motion techniques. Sediment pathways were observed using a novel technique, where regions of interest were filmed at 60 frames per second under ultra violet light, illuminating painted tracers. Three paint colors were used for different size tracers, which allowed us to apply image segmentation and create separate videos for three size fractions of the sediment. Pathways were then extracted using Lagrangian tracking software. Results show that the area of active transport is limited to a narrow portion of the channel width that increases with flood stage. At low flow, transport is routed along the toe of point bars, while no particles travel into the region of the pool, where the bed is uncovered. Riffles are rarely observed at these stages. As the flow increases, the lateral extent of active transport expands to include the higher parts of the bars, while connective riffles grow in areal extent and height. Erosion and deposition was found to occur more readily along the active sediment transport zones. Pathways varied by particle size so that smaller particles traveled higher over the point bar and large particles tended to collect in the riffle. These results indicate that sediment-routing is a dominant mechanism behind the formation and maintenance of riffles in meandering rivers. Future work to quantify these processes will increase the effectiveness and longevity of river remediation design through targeted sediment augmentation instead of bedform reconstruction.
A Methodology for Design and Adaptation of Infrastructure Under Deep Climate Uncertainty
(University of Waterloo, 2024-01-03) Barkhori Mehni, Mohammad
Proper decision-making in design, and adaptation management of infrastructure is essential, in the face of environmental uncertainties. As and example, current climate change models yield a range of widely diverging projections, rendering the allocation of climate change readiness investments increasingly complicated. While a severe climate change scenario may necessitate extensive adaptation investments, realization of a mild or moderate environment after costly system modifications or early adoption of costly adaptation measures would also result in a sense of loss. An alternative approach is resorting to adaptive solutions that commence with reduced costs until the environmental circumstances become more evident. With the goal of minimizing the sense of loss associated with decision-making, this research integrates the concept of regret into a decision-making framework. Regret serves as a quantifiable metric, capturing decision-makers' desire to mitigate the sense of loss resulting from making incorrect choices. Additionally, the framework incorporates the potential of gaining information over time about climate as it occurs through a dynamic programming scheme. The research encompasses three studies. Firstly, common design and decision-making approaches are evaluated within the context of climate change. Specifically, an investigation into the nonstationary effects of wind load on structural reliability under the impact of climate change was conducted using several methods. The findings reveal that, under the worst scenario, the lifetime probability of failure can be around twice as high as the baseline without climate change. However, such a scenario-based analysis is not conclusive in decision-making. To facilitate decision-making in the face of deep climate uncertainty, an innovative methodology is developed and then tested in a second study on bridge corrosion management. In this study, the methodology offers a straightforward decision-making approach when considering the implementation of costly corrosion protection measures in an unknown environment. Additionally, a sensitivity analysis aids in discerning project types and determining the optimal course of action, whether it involves waiting or investing in field testing. Finally, the third study is an application of the methodology in the context of climate change by addressing the design and managed adaptation of a river-crossing bridge exposed to climate change-induced scour. The study showcases how the methodology can assess trade-offs among different design options and determine the optimal course of action, given the uncertainties surrounding future climate scenarios. By evaluating the trade-offs between inaction and costly adaptations, the research identifies conditions under which a wait-and-see approach is effective and when incorporating design flexibilities for future adaptations is warranted. Furthermore, the method's performance is evaluated, and a comparison of various decision-making methods for adaptation is presented. The analysis demonstrates that in the case study, incorporating the potential for information arrival can yield up to $3.5 million in benefits, where an indirect cost of failure amounts to $10 million. Consequently, this framework empowers designers and asset managers to navigate the uncertainties of climate change in their decision-making processes effectively. The outcomes of this research contribute to the advancement of decision-making approaches for infrastructure design and adaptation in the face of climate uncertainties. By integrating deep uncertainties into decision-making processes and proposing an innovative methodology, this research assists infrastructure owners, managers, and policymakers in enhancing the resilience and long-term sustainability of infrastructure systems in an uncertain future climate.
Performance of Soil Borehole Thermal Energy Storage System under Different Natural and Engineered Subsurface Conditions
(University of Waterloo, 2023-12-18) Pandey, Upasana
Borehole thermal energy storage (BTES) system, a type of underground thermal energy storage (UTES) systems, is a promising technology for sustainable space heating. BTES stores thermal energy in subsurface media (rock or soil) using borehole heat exchangers (BHEs). BTES installed in soil are specifically known as soil borehole thermal energy storage (SBTES) system. In SBTES, a heat carrier fluid (HCF) collects thermal energy from various heat sources such as solar energy and industrial waste heat, circulating it through the BHEs. The heat from the BHEs is transferred to the surrounding soil and stored as thermal energy in the soil deposits, thereby increasing its temperature. Subsequently, the stored energy is extracted through BHEs for space heating applications. The ability to retain stored energy in soil deposits depends on subsurface thermal and hydraulic conditions. Previous studies have explored various subsurface conditions (saturated, unsaturated, and groundwater flow) to capture their influence on the thermal performance of SBTES system. While previous studies focused specifically on the role of soil thermal conductivity under saturated soil conditions, the influence of other soil properties, particularly under different SBTES design conditions, has not been systematically explored. In unsaturated subsurface conditions, studies have concentrated on assessing the thermal performance of SBTES systems under varying moisture content conditions, while considering different water retention parameters. However, the understanding of the role of soil porosity in the thermal performance of SBTES in unsaturated soil, particularly under long-term operation scenarios, is limited. Additionally, existing studies have predominantly examined homogeneous soil conditions and have not accounted for soil layering. Further, while some studies have explored the impact of seasonal climatic fluctuations, they have primarily focused on variations in seasonal surface temperatures alone. The effect of surface pressure variations induced by factors such as evapotranspiration, groundwater table fluctuations, and other climatic conditions has not been thoroughly investigated. Previous studies regarding groundwater flow consideration often assumed the groundwater table to be flush with the ground surface, with the BHEs completely submerged into the groundwater. However, when different groundwater table depths are considered, where the BHEs are partially submerged, these studies did not take into account the influence of flow velocity. Previous studies have established that the consideration of groundwater flow is important in the analysis and design of SBTES systems. However, there is no systematic study available that explores the SBTES performance for a wide range of flow velocities and for multiple groundwater table depths considered in conjunction. Additionally, in the presence of high velocity groundwater flow, it is commonly recommended to avoid installing SBTES at the location without proper engineering modifications. However, currently no strategies exist to effectively mitigate the adverse effects of groundwater flow on the thermal performance of SBTES systems. The aim of this study is to develop better understanding of the influence of different subsurface conditions on the thermal performance of SBTES system through rigorous numerical analysis. The analysis incorporates saturated, unsaturated, and groundwater flow conditions to capture their respective impacts. Initially, a simplified conduction-based model is used to investigate the influence of physical and thermal properties of soil under different BHE spacing and injection heat flux scenarios for saturated soil condition. Subsequently, for unsaturated soil conditions, a coupled heat and mass transfer based numerical model is used to investigate the thermal behavior of SBTES systems under various subsurface moisture conditions, encompassing fully dry, fully saturated, and varying moisture content scenarios with different depths of the saturated soil zone. Additionally, the study examines the impact of seasonal surface pressure variations on the thermal performance of the SBTES system in unsaturated soil. Further, the role of soil porosity under different soil stratifications and soil moisture conditions on the thermal performance of the SBTES system in unsaturated soil is investigated to augment the existing knowledge in this area. The effects of groundwater flow on the short- and long-term performances of SBTES systems under fixed- and variable-energy supply and demand conditions are studied for different groundwater velocities and different groundwater table depths. Numerical simulations of a SBTES system are performed for four groundwater table depths and with four groundwater velocities ranging from 0 m s−1 to 1 × 10−5 m s−1. The study aimed to highlight the importance of conducting long-term analyses and quantifies the adverse effects of groundwater flow on the thermal performance of SBTES. Finally, a design aid is proposed in the form of vertical barriers to be installed within the SBTES domain, aimed at mitigating thermal losses resulting from groundwater flow. A comprehensive study is conducted to provide recommendations regarding the suitable type of vertical barriers, their appropriate positioning with respect to SBTES domain, and the anticipated improvement in thermal performance of SBTES system upon integration with the vertical barrier as a design aid. A detailed analysis is conducted for small, medium, and large-scale SBTES domain to provide a suitable range of vertical barrier design components, refining the geometry of the vertical barrier to achieve optimal thermal performance.
Comparison of Condition Evaluation Methods for Flexible Pavement, and Exploration of Ride Quality Assessment through Vibration Frequency Analysis
(University of Waterloo, 2023-12-12) Zhang, Tianshu
This thesis reviews and compares evaluation standards, distress manifestation manuals, and key performance indices for flexible road asset management across North America. Evaluation of pavement structural and functional conditions for a road section is one of the crucial steps in determining pavement maintenance and rehabilitation strategies, as well as investment plans for road asset management. However, different evaluation methods applied to the same road section may result in notable variations of pavement condition assessments, as investigated by this study, and this often varies with different regions and road agencies. In this thesis, sixteen pavement condition rating manuals are reviewed to identify differences and similarities. A trend of simplification in the pavement evaluation process is observed in pavement rating manuals, and a potential solution involving the reduction in the types of pavement distresses, according to their manifestation correlation, is proposed. The thesis also explores a new method for assessing ride quality through vibration frequency analysis. The evaluation processes generally consist of four components: surface distress, roughness, safety evaluation, and structural strength. Roughness, as a critical factor directly influencing the driving experience, has a close correlation with ride comfort. However, the existing pavement roughness assessment method lacks a correlation with vehicle vibration, thereby restricting its capacity to comprehensively reflect its influence on ride comfort. A car simulation model is constructed using MATLAB Simulink, and 20 road sections are tested. The simulation's vibration signals are analyzed in the frequency domain using Fast Fourier Transform (FFT). A new index, the Ride Resonance Index (RRI), is introduced based on human resonance effect evaluation in the frequency domain during driving. A moderate linear relationship is found between RRI and pavement roughness. In summary, the diversity of evaluation methods and standards among different regions and agencies underscores the need for harmonization and simplification. The observed moderate linear relationship between RRI and International Roughness Index (IRI) suggests that it could serve as a promising supplementary indicator for evaluating pavement conditions.
Development of a novel methodology for the determination of the total solar energy transmittance of Building-Integrated Photovoltaic window technologies using outdoor measurements
(University of Waterloo, 2023-12-11) Eskandar, Sara
The urgent need to combat global warming and transition towards sustainable energy sources has focused attention on the building sector, a major contributor to energy consumption and greenhouse gas emissions. To achieve net-zero energy building performance, a comprehensive approach is essential, involving energy conservation measures, enhanced building systems efficiency, and integrating on-site renewable energy generation. Within this context, the integration of photovoltaic window technologies become essential for the generation of renewable electricity and reduction of solar heat gains which impacts building heating, cooling, and electric lighting loads as well as visual and thermal comfort. The aim of this thesis is to introduce the theoretical background of a novel experimental methodology for the determination of total solar energy transmittance (TSET) of building-integrated photovoltaic (BIPV) windows using outdoor measurements. Existing studies and standards dictate the use of indoor test facilities consisting primarily of a hot box calorimeter where the window is mounted and characterized under a steady state solar simulator. The calorimetric (thermal) methods require steady state conditions that have been proven challenging to achieve for windows that incorporate advanced shading devices or photovoltaic cells, potentially resulting to significant measurement errors of the TSET. Also, these studies rarely characterize the angular dependency of TSET. To overcome these challenges, a novel experimental methodology is proposed to measure TSET using optical measurements under outdoor conditions. The experimental setup uses pyranometers (for solar transmittance measurements), pyrheliometer (for direct incident measurements), several Resistance Temperature Detector (RTD) sensors and infrared cameras (for surface temperature measurements), allowing the determination of TSET (and its angular dependency) based on a series of instantaneous outdoor measurements under sunny conditions that could result to reliable and repeatable TSET values. For the case of BIPV windows, a load at maximum power point (MPP) is connected to the window, allowing the maximum fraction of the absorbed solar energy to be converted into electricity. Finally, a new approach is proposed for the conversion of measured TSET to TSET under standard conditions, using a reference window of known TSET. The unique aspects of the proposed TSET methodology are: i) the use of optical measurements ii) performed under transient outdoor test conditions. Current standard TSET calorimetric tests use thermal measurements that require long window conditioning under steady state conditions. The new methodology is also able to perform TSET measurements under a range of solar angle of incidence (i.e., 0 to 60 degrees), including normal TSET. The limitation of the proposed methodology is that it is not applicable to products with angular selective properties (e.g., microshade film). While it is developed for BIPV windows, and can be applied for TSET determination of coated, reflective, and electrochromic windows, under outdoor test conditions. In summary, a novel experimental methodology is proposed for the determination of the total solar energy transmittance of Building-Integrated Photovoltaic windows using outdoor measurements. The proposed methodology aims to provide a framework to quick, accurate, consistent, and repeatable approach to TSET testing that can potentially be standardized for BIPV windows and other advanced window technologies. The proposed methodology intends to support the advancement of sustainable building practices, enhance energy efficiency, and foster the integration of renewable energy technologies into building design and construction, paving the way for a more sustainable built environment.
Real-Time Traffic Performance Measurement of Signalized Intersections Using Connected Vehicle Data: A Simulation-Based Study
(University of Waterloo, 2023-12-05) Wang, Yubo
Traffic congestion has long become a major concern in many cities in Canada and around the world. It has been estimated that the annual total economic loss due to traffic congestion in major Canadian urban centers has reached nearly $4 billion. Real-time monitoring of traffic conditions and measurement of the performance of the underlying traffic management systems is a critical requirement for mitigating and minimizing the impact of traffic congestion in an urban road network. The latest advance in the Connected Vehicle (CV) technology has afforded a new opportunity for developing solutions that make use of high-resolution trajectory data for real-time urban traffic monitoring and performance measurement, such as Automated Traffic Signal Performance Measures (ATSPM). However, many critical issues still need to be addressed before the potential of CV can be fully realized. For example, in the context of ATSPM, what traffic performance measures could be derived from the CV data? Can non-recurrent congestion be detected in real-time and at what latency? What would be the optimal spatial and temporal data aggregation resolutions of CV data? What would be the effect of the CV market penetration rate on the reliability of specific performance measures? This research attempts to address some of these questions through a simulation study of a real-world signalized urban arterial corridor from Broward County, Florida, US, consisting of 17 signalized intersections with a wide range of layouts and congestion levels. An extensive set of simulation experiments have been conducted under a range of scenarios varying by facility types (single intersection vs. corridor), congestion level (from undersaturated to oversaturated), CV market penetration rates (1%-25%), and signal timing plans. Under each scenario, samples of vehicles at specific market penetration rates are randomly drawn from the simulated traffic population to represent the CVs and their trajectory data are used to calculate various signal performance measures, including average overall delay, percentile queue length, percentage of stopped vehicles and an average number of stops, at the spatial aggregation levels of movements, approaches, intersections, and corridor. A sensitivity analysis is subsequently conducted to assess the accuracy and reliability of the performance measures derived from CV data as related to some specific external conditions and factors. The results from the simulation experiments have underscored the significant potential of CV data, even under the current relatively low market penetration rate, for estimating various important traffic performance measures and detecting non-recurrent events or bottlenecks - a basic requirement for implementing ATSPM.
Reliability-based Environmental Impact Assessment in Geotechnical Engineering
(University of Waterloo, 2023-11-30) Lee, Mina
A sustainable design is achieved by balancing the four aspects, so called the four Es, of sustainability – environment, economy, equity, and engineering. Given that geotechnical constructions involve land transformations through earthworks and construction of large-scale concrete and/or steel structures (e.g., bridge abutments, retaining structures, and tunnels), geotechnical engineering can play a vital role in sustainable development by ensuring that the resources are consumed responsibly with minimal emissions to the environment. In this thesis, methodology frameworks, developed based on (i) environmental impact assessment, (ii) reliability-based design, and (iii) multi-objective optimization, are proposed to facilitate the process of sustainable design in geotechnical engineering. The frameworks are applied to common geotechnical structures such as drilled shaft foundation, pile group, and mechanically stabilized earth (MSE) wall. To quantify the environmental sustainability of geo-structures, life cycle assessment (LCA) is used. LCA utilizes inventory of energy and materials to calculate the emissions from the life cycle stages and characterize the emissions into environmental impacts. In this thesis, the procedures of LCA, which have been tailored to geotechnical applications, are demonstrated meticulously with detailed sample calculations to encourage the use of LCA in standard design practices and to demonstrate the usefulness of information obtained from LCA. In fact, for example, it was found, based on this research study, that the global warming impact and human toxicity of a typical drilled shaft are 39 and 486% of annual world impact per person, respectively. The use of reliability-based design (RBD) methods has been strongly promoted in the last two decades to better tackle the uncertainties involved in design and soil parameters; hence, the connection between important factors in RBD and environmental impacts is investigated in this thesis. A comprehensive analysis is conducted on the relationship between reliability and global warming impact of geotechnical designs (i.e., drilled shaft and MSE wall) considering uncertainties in soil properties, material properties, applied load, model, and design dimension. Parametric and sensitivity studies are systematically conducted using reliability analyses, like first-order reliability method (FORM) and Monte Carlo simulations, and LCA. To balance the multiple aspects of sustainability, a multi-objective optimization framework is proposed using which designers can determine design dimensions that aim for minimizations of cost and global warming impact and maximization of reliability of a geotechnical structure. The framework utilizes several methodologies including LCA, FORM, response surface methodology, and non-dominated sorting genetic algorithm (NSGA-II). To encourage sustainability considerations in geotechnical engineering design, charts are developed which are useful for determining (i) global warming impact of the geo-structures designed with working stress design (WSD) and RBD approaches and (ii) design dimensions optimized with respect to cost, engineering reliability, and environmental impact, without the use of and knowledge in the sophisticated methodologies incorporated in the proposed frameworks.

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