Civil, Geological and Environmental

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Land use and river-lake connectivity: Biodiversity determinants of lake ecosystems
(Elsevier, 2024-04-25) Xie, Huiyu; Ma, Yu; Jin, Xiaowei; Jia, Shiqi; ZHAO, Xianfu; Cai, Yongjiu; Xu, Jian; Wu, Fengchang; Giesy, John
Lake ecosystems confront escalating challenges to their stability and resilience, most intuitively leading to biodiversity loss, necessitating effective preservation strategies to safeguard aquatic environments. However, the complexity of ecological processes governing lake biodiversity under multi-stressor interactions remains an ongoing concern, primarily due to insufficient long-term bioindicator data, particularly concerning macroinvertebrate biodiversity. Here we utilize a unique, continuous, and in situ biomonitoring dataset spanning from 2011 to 2019 to investigate the spatio-temporal variation of macroinvertebrate communities. We assess the impact of four crucial environmental parameters on Lake Dongting and Lake Taihu, i.e., water quality, hydrology, climate change, and land use. These two systems are representative of lakes with Yangtze-connected and disconnected subtropical floodplains in China. We find an alarming trend of declining taxonomic and functional diversities among macroinvertebrate communities despite improvements in water quality. Primary contributing factors to this decline include persistent anthropogenic pressures, particularly alterations in human land use around the lakes, including intensified nutrient loads and reduced habitat heterogeneity. Notably, river-lake connectivity is pivotal in shaping differential responses to multiple stressors. Our results highlight a strong correlation between biodiversity alterations and land use within a 2e5 km radius and 0.05e2.5 km from the shorelines of Lakes Dongting and Taihu, respectively. These findings highlight the importance of implementing land buffer zones with specific spatial scales to enhance taxonomic and functional diversity, securing essential ecosystem services and enhancing the resilience of crucial lake ecosystems
Spatial and temporal changes in small-strain shear modulus of geogrid-stabilized crushed aggregate materials
(Elsevier, 2025-01-16) Yesnik, Chelsey; Soliman, Haithem; Morozov, Igor; Fleming, Ian; Landry, Ethan
Geogrid stabilization can be used by transportation agencies to build durable roadways over soft subgrade soil. The performance of geogrid stabilization is highly dependent on the properties of the geogrid material, the aggregate material, and the interaction between the two materials when combined. Therefore, transportation agencies need to perform their own studies to assess the performance of geogrid stabilization for their local materials. Additionally, the current knowledge base needs to be continually expanded to a variety of aggregate-geosynthetic composites to develop performance-based design methods for geosynthetic-stabilization. This study evaluates the long-term performance of two geogrids used to stabilize a crushed aggregate material. A full-scale traffic loading system was built to simulate a full half-axle (40kN) traffic load for thousands of load cycles. Two trials were completed using the same crushed aggregate material. For each trial, two geogrid-stabilized sections, and one control section were evaluated. The performance of the test sections was monitored for 4000 load cycles by measuring surface rutting and completing multichannel analysis of surface waves (MASW) to measure aggregate stiffness. Results showed that the geogrid-stabilized sections had better long-term performance than the control sections with lower degradation of the as-built aggregate stiffness. There was good agreement amongst the MASW results, rutting measurements, and Shakedown analysis. It has been concluded that MASW is an effective method for evaluating the long-term performance of geogrid stabilization in aggregate layers with a customized instrumentation plan according to the targeted measurements.
Sub-zero soil CO2 respiration in biostimulated hydrocarbon-contaminated cold-climate soil can be linked to the soil-freezing characteristic curve
(Environmental Science and Pollution Research, 2025-01) Nayeema, Tasnim; Lee, Aslan Hwanhwi; Richter, Amy; Ng, Kelvin Tsun Wai; Chang, Wonjae
Extending unfrozen water availability is critical for stress-tolerant bioremediation of contaminated soils in cold climates. This study employs the soil-freezing characteristic curves (SFCCs) of biostimulated, hydrocarbon-contaminated cold-climate soils to efficiently address the coupled effects of unfrozen water retention and freezing soil temperature on sub-zero soil respiration activity. Freezing-induced soil respiration experiments were conducted under the site-relevant freezing regime, programmed from 4 to − 10 °C at a seasonal soil-freezing rate of − 1 °C/day. The effects of unfrozen water retention on extending soil respiration activity emerged at the onset of soil-freezing. The unfrozen water effect became significant below 0 °C (correlation r = 0.83–0.94) and comparable to the temperature effect (correlation r = 0.82–0.90), successfully demonstrating the coupled effects on sub-zero respiration activity. Soil CO2 respiration modelling based on the temperature dependency only (Arrhenius and Q10 models) did not accurately describe sub-zero respiration activity associated with increased unfrozen water retention in treated contaminated soils. The shifted SFCCs of the treated soils, expressed as a function of soil temperature (T) and unfrozen water content (θ), served as a key framework for efficiently developing the sub-zero respiration model (SFCC-RESP). The developed SFCC-RESP model closely approximated the changes in soil respiration rates influenced by T and θ in the treated soils (R2 = 0.94–0.98) and described the abrupt decrease and subsequent stabilization in CO2 production during the transition to the deeply frozen soil phase. The SFCC-RESP model integrated with soil thermal models (TEMP/W) can be used to produce spatial distributions of T, θ, and CO2 production in the treated soil matrix, providing a tool to approximate the abundance of unfrozen habitable niches when developing cold-tolerant bioremediation strategies.
The impact of non-uniformity and resistivity on the homogenised corrosion parameters of rebars in concrete – a circuit model analysis
(Corrosion Engineering, Science and Technology: The International Journal of Corrosion Processes and Corrosion Control, 2023-06) Li, Gang; Evitts, Richard; Boulfiza, Moh
When rebar corrosion parameters are characterised from an electrochemical polarisation curve, the non-uniform rebar surface conditions need to be considered. In this research, a circuit model was developed to simulate the polarisation behaviour of rebar in concrete. It is found that the resistivity of concrete leads to non-uniform potential on the rebar, which causes the polarisation curve of the entire rebar to deviate from the Butler–Volmer kinetics. This, in turn, leads to an overestimation of the Tafel constants and the corrosion current density. Such deviations are more pronounced with higher concrete resistivity, especially when the active and passive rebar surfaces have a similar area ratio. The study recommends using potentiodynamic scans of representative reinforced concrete samples of the field conditions or the calculated parameters using an averaging technique, such as the proposed circuit model, to obtain accurate E-I curves or parameters for electrochemical modelling and corrosion rate prediction.
Developing a universal equation to estimate the mass of dewatered wastewater sludge during biological digestion at mesophilic and thermophilic temperatures
(Water Science & Technology, 2024-11) Poorasgari, Eskandar; Örmeci, Banu
A series of dewaterability tests were conducted on various types of sludges to establish a wholistic relationship between sludge water fractions. Sludge samples were obtained from batch and continuous sludge digesters, which were operated anaerobically and aerobically under mesophilic and thermophilic conditions. Dewaterability of the sludge samples and the distribution of water fractions were studied using centrifugation and thermal drying. Thickened waste activated sludge (T-WAS) contained 10-11 g bound water (BW)/g of total solids (TS), and it was more hydrophilic than primary and digested sludges. During anaerobic digestion, BW content fluctuated between 3.2 and 4.2 g BW/g TS. However, aerobic digestion at 55°C reduced the BW content of the mixed T-WAS + primary sludges from 3.7 to 2.1 g BW/g TS. A linear function was developed to correlate supernatant and BW mass fractions (R2 = 0.995). An equation was derived from the linear function to estimate the mass of dewatered sludge based on the TS concentration of the initial wet sludge. The developed expression is applicable to different kinds of wastewater sludges. Such an expression would be helpful for the designers and operators of sludge thickening and dewatering systems that use centrifugal separation.
A universal empirical equation to estimate the abundance of carbapenem-resistant genes during aerobic digestion of wastewater sludge
(Water Practice & Technology, 2024-11) Poorasgari, Eskandar; Örmeci, Banu
Carbapenem-resistant genes (CRGs) exist in wastewater and accumulate in wastewater sludge. Due to the potential threat posed by the CRGs, it is important to quantify CRGs and predict their removal and discharge concentrations during aerobic sludge digestion. Nonetheless, gene quantification is tedious, error-prone and expensive. This study aims to develop multiple regression models to estimate CRGs from sludge parameters that are routinely measured for the monitoring and design of aerobic sludge digesters. Batch reactors were operated at mesophilic and thermophilic temperatures for 20-35 days. Sludge samples were periodically taken during aerobic digestion. Three CRGs (blaGES, blaOXA-48 and blaIMP-27) together with 16S rRNA and integron class 1 genes were quantified. Aerobic digestion reduced the abundance of all target genes. Multiple regression modelling was conducted in linear (LM) and non-linear (NLM) modes. Sums of squared errors of the LM models were 0-0.048, whereas those of the NLM models were 0–0.003. Adjusted R2 ranges of the LM and NLM models were 0.774–0.931 and 0.986–1, respectively. Overall, the NLM models predicted the abundance of target genes more accurately than the LM models. NLM models may be used to modify the design and operational parameters of aerobic sludge digesters.
Sustainable enhancement of biogas production from a cold-region municipal wastewater anaerobic digestion process using optimized sludge-derived and commercial biochar additives
(Elsevier, 2024-10-11) Zeynali, Rahman; Asadi, Mohsen; Ankley, Phillip; Esser, Milena; Brinkmann, Markus; Soltan, Jafar; McPhedran, Kerry M.
Anaerobic digestion (AD) of municipal wastewater sludges produces valuable solid digestate and biogas. Biogas is a source of clean energy and enhancement of its production has been of recent interest for increased electricity generation, among other products. The objective of this study was the development of a novel municipal sludge-derived biochar and its application in a municipal wastewater AD system to increase the biogas production rate. Thickened waste-activated sludge (TWAS) samples were collected from the cold-region municipal wastewater treatment plant and used to synthesize biochar applied in the simulation of AD processes using laboratory-scale reactors. The TWAS-derived biochar was synthesized using the commonly used furnace pyrolysis (sludge-based biochar, SBC), and more novel microwave pyrolysis including phosphoric acid as a microwave activator (activated sludge-based biochar, ASBC). The microwave pyrolysis conditions were optimized using a computational fluid dynamics (CFD) technique. In addition, various commercially available carbon-based additives were assessed for their impacts on the AD process including activated carbon, wood-derived biochar, and forest residue-derived biochar. Results showed that the ASBC increased the cumulative methane production by 50% (333 mL/g VS) versus the control sample (221 mL/g VS) after 30 d. The ASBC showed higher surface area, electrical conductivity, and metal contents versus the other biochars which boosted the AD microbial community growth leading to higher organic matter conversion into biogas. In the ASBC-amended digesters, the bacterial phylum Bacteroidota, which contains a major genus of the dgA-11-gut-group, exhibited a synergy between organic substrate fermentation and volatile fatty acid production, resulting in enhanced biogas production. The TWAS biochar demonstrated promising performance in enhancing the AD process fostering energy and resource self-sufficiency at municipal wastewater treatment plants. This smart sludge management aligns well with sustainable waste management practices and clean energy production strategies, especially considering that the biochar was sourced from a readily available continuous waste-product stream.
Assessment of Rapid and Conventional RT-qPCR-Based Systems for Wastewater Surveillance
(ACS Publications, 2024-09-05) Asadi, Mohsen; Hamilton, Daniel; Shomachuk, Corwyn; Oloye, Femi F.; De Lange, Chantel; Liang, Jiaqi; Xia, Pu; Osunla, Charles A.; Cantin, Jenna; Mejia, Edgard M.; Gregorchuk, Branden S. J.; Becker, Michael G.; Mangat, Chand; Brinkmann, Markus; Jones, Paul D.; Giesy, John P.; McPhedran, Kerry M.
Conventional wastewater surveillance (WS) relies on highly trained personnel, advanced instrumentation, and significant resources, making the development and use of simple, rapid, and sensitive alternative technologies valuable for reducing costs, time, and labor intensity. For the first time, this study investigated the use of two well-developed rapid systems, including the GeneXpert and LuminUltra, in parallel with a conventional WS reference methodology for the assessment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in three cities: Saskatoon, Prince Albert, and North Battleford, Saskatchewan, Canada. RNA extractions from wastewater samples were carried out for the conventional reference and LuminUltra methods, while GeneXpert was used for both raw and concentrated wastewater samples. Bland–Altman plots showed a combination of systematic bias and random error between these real-time reverse transcription-quantitative polymerase chain reaction (RT-qPCR)-based systems. Additionally, results indicated the reasonable performance of GeneXpert in viral detection with a sensitivity rate of >98%, as compared to the conventional reference methodology of 100% and LuminUltra with >65%. A Spearman correlation test showed meaningful relationships between the GeneXpert and conventional reference methodology viral level results across all cities, indicating GeneXpert’s reliability for accurate viral detection and disease prevalence determination, specifically in limited-resource communities, with a shorter processing time and cost-effectiveness in analysis.
Hydraulic Structures
(Saskatoon: Smith, 1995) Smith, C.D.
This book presents general information on the form and function of many types of hydraulic structures and to give detailed theory and design procedures on some of the more common ones. The application of principles is intended to be sufficiently rigorous that a student of the subject will gain a working knowledge of the basic procedures used in hydraulic design. While, of necessity, certain design procedures are empirical, this book is not concerned with the "how" aspect of hydraulic design alone. Equal emphasis is placed on the "why" aspect, since it is only through this approach that the engineer can properly assess the merits of a proposed design for a specific application.

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