Canadian Journal of Civil Engineering
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A review of the environmental pollution originating from the piggery industry and of the available mitigation technologies: towards the simultaneous biofiltration of swine slurry and methaneThis article is one of a selection of papers published in this Special Issue on Biological Air Treatment. In Canada, the piggery industry is an essential part of the agricultural sector, but the main waste product of this industry, swine slurry, is particularly harmful to the environment. The anaerobic storage conditions and the excessive use of slurry for agricultural fertilization contribute, respectively, to the emission of greenhouse gases and to aquatic pollution. This paper provides a review of these environmental concerns and of the existing mitigation technologies. Water pollution from swine slurry is associated with the nutrients it contains, such as nitrogen and phosphorous, while the main greenhouse gases produced by the piggery industry are methane and nitrous oxide. Available technologies can valorize the slurry through agricultural fertilization, reduce greenhouse gas emissions, by limiting nutrient availability for example, or treat the effluents using solid–liquid separation, flaring or biological processes. Specific attention is paid to biofiltration due to its potential to simultaneously treat these two types of pollution.
Canadian Journal of Civil Engineering - Tập 36 Số 12 - Trang 1946-1957 - 2009
Mathematical modelling of a circular clarifier A numerical model has been developed to predict the velocity distribution and the concentration distribution for a nonuniform flocculated particle suspension for turbulent density stratified flow in secondary clarifiers. This model consists of a set of conservation equations for fluid mass and momentum and sediment concentration as well as a relationship for solids settling velocity. The turbulent stresses are calculated using the eddy-viscosity concept and the k-ε turbulence model. Since the strong local numerical instabilities near the reaction baffle lip, where the low-solids concentration surface return flow joins the high solids concentration bottom current, was successfully overcome in the iterative solution procedure, the calculation zone in this investigation can be extended to take into account the inlet zone of the clarifier. The model gave a satisfactory description of the influence of the density variations on the hydraulic regime and the solids concentration distribution in the clarifier. A good agreement was obtained between the experimental data and the numerical simulation. Key words: clarifier, numerical model, density stratification, turbulence.
Canadian Journal of Civil Engineering - Tập 19 Số 3 - Trang 365-374 - 1992
Hydrodynamic of circular primary clarifiers The strip integral method has been applied to a typical restricted inlet circular primary clarifier, in order to simulate the flow pattern and dispersion characteristics of the flow. This method assumes a dominant flow direction and with the use of velocity shape functions reduces the equations of motion and continuity to a set of simultaneous ordinary equations. Three shapes were chosen, corresponding to the boundary layer, the potential core, and the free mixing and recirculation zone. A Runge–Kutta method was used to integrate the set of ordinary differential equations. A standard finite element method was used in the withdrawal zone. The numerical predictions compared favorably with experimental velocity distributions obtained in a physical model of circular sedimentation tanks. The model is restricted to circular primary clarifiers of discrete suspension with low concentration operating at neutral density environment.The model was used to predict the velocity and dispersion characteristics of the circular tanks used at the West Windsor Pollution Control Plant, Windsor, Ontario.
Canadian Journal of Civil Engineering - Tập 11 Số 2 - Trang 299-307 - 1984
Effects of detailing on panel zone seismic behaviour in special moment resisting frames with unequal beam depths Special moment resisting frames (SMRF) are commonly used as lateral-load resisting systems in seismic design. The results of recent studies have shown that the seismic performance of such frames can be improved by paying particular attention to the detailing of their panel zones (PZ) and beams. Panel zones with unequal beam depths appear to be a special case of connection detailing, which has not received sufficient attention so far and could lead to complications in everyday engineering practice. Some full-scale experiments of connections with unequal beam depths were performed, using different continuity plate arrangements (inclined and straight plates), and different corner clip lengths. A companion analytical study was also conducted, for which results have shown that the correct selection of inclined or straight continuity plates, with special detailing of the PZ, could keep the behaviour of the latter within safe margins. Such considerations could prevent the occurrence of failure in the PZ, and significantly improve the seismic resistance of SMRF with unequal beam depths.
Canadian Journal of Civil Engineering - Tập 39 Số 4 - Trang 388-401 - 2012
Intensity and characteristic length of braided channel patternsThis paper is one of a selection of papers in this Special Issue in honour of Professor M. Selim Yalin (1925–2007). Recent research on braided river morphology shows that the intensity (number of anabranches) of braiding channels increases with dimensionless discharge and (or) stream power. This variation in intensity reflects the adjustment of total sinuosity of the river to imposed gradient at a given discharge and grain size. Only a subset of channels is active at a given time and this active braiding intensity reflects the limited number of channels that can sustain bed load transport as the flow is divided. This is governed mechanistically by the dynamics of bifurcations and avulsions. Braided channel networks also have a characteristic length scale (or scales) related to the wavelength of the bars from which braiding develops and to the scale of the bars and confluence–bifurcation units within the braided network. The range of scales is limited by the size (and, therefore, number) of the active channels within the network and the width of the entire river.
Canadian Journal of Civil Engineering - Tập 36 Số 10 - Trang 1656-1666 - 2009
Fatigue damage analysis in asphalt concrete mixtures using the dissipated energy approach An asphalt concrete damage–energy fatigue approach based on the concept of change in dissipated energy is presented in this paper. The damage–energy based fatigue approach is simple and based on a sound theoretical background. The central concept of the energy approach is the energy fatigue curve, which is based on two key elements, namely the plateau value (PV) and the number of load cycles to true failure (Ntf ). The plateau value represents the constant value of the percentage of dissipated energy that produces damage to the material under cyclic loading. Failure is defined as the number of load cycles at which this percentage of dissipated energy begins to increase rapidly, indicating instability. Flexural fatigue testing was used to test hundreds of asphalt concrete beams, mainly under controlled-strain testing conditions. It was found that PV is highly dependent on the initial loading conditions, stress, strain, and dissipated energy. As a result, it can be used conveniently in pavement design. The number of load cycles to 50% reduction in initial stiffness was found to be highly correlated with the new failure point (Ntf ). Using the dissipated energy concepts in fatigue analysis makes it possible to account for damage accumulation in a straightforward manner.Key words: fatigue of asphalt concrete, dissipated energy, damage, energy ratio.
Canadian Journal of Civil Engineering - Tập 33 Số 7 - Trang 890-901 - 2006
Chlorine and UV disinfection of ampicillin-resistant and trimethoprim-resistant <i>Escherichia coli</i>A paper submitted to the Journal of Environmental Engineering and Science. This bench-scale study investigated whether strains of Escherichia coli that are resistant to two common types of antibiotics, ampicillin and trimethoprim, possess increased resistance to two common disinfectants in water and wastewater treatment, free chlorine and ultraviolet disinfection, relative to an antibiotic-sensitive strain of E. coli isolated from sewage sludge. Trimethoprim-resistant E. coli was slightly more resistant to chlorine than the antibiotic-sensitive isolate and the ampicillin-resistant E. coli under the study conditions (95% confidence), however this difference would not be important under normal chlorination conditions applied in practice. There were no statistically significant differences between the ultraviolet dose-response profiles of the antibiotic-resistant and antibiotic-sensitive E. coli strains over the ultraviolet dose range tested.
Canadian Journal of Civil Engineering - Tập 36 Số 5 - Trang 889-894 - 2009
A new type of ductile composite reinforcing bar with high tensile elastic modulus for use in reinforced concrete structures A new core-shell model of hybrid composite bar has been developed, in which steel and glass fibers are randomly dispersed across the cross section of the core, and Twaron (Teijin Twaron, the Netherlands) and carbon fibers placed within the shell. Compared with glass composite reinforcing bars, the new hybrid composite bars possess characteristics of corrosion resistance, ductility, and high tensile elastic moduli and strength, and have potential for application in concrete structures.
Canadian Journal of Civil Engineering - Tập 36 Số 4 - Trang 672-675 - 2009
Damage to buildings due to the 1989 Loma Prieta earthquake — a Canadian code perspective Damage to building structures during the October 17, 1989, Loma Prieta earthquake prompted site visits by the authors. This paper presents examples of damage to buildings constructed with reinforced concrete, steel, masonry, and timber. The observed damage is used to illustrate some of the seismic design clauses in the 1990 National Building Code of Canada, the 1984 Canadian Standards Association (CSA) Standard for the Design of Concrete Structures for Buildings, and the 1989 CSA Standard for the Limit States Design of Steel Structures. The important roles played by the presence of soft soil, poor structural layouts, inadequate detailing, the lack of reinforcement in masonry, as well as inadequate connections to foundations are highlighted. Examples of the performance of upgraded structures are also given, and the concern over the presence of existing hazardous buildings in significant seismic zones in Canada is emphasized. Key words: seismic design, earthquake, Loma Prieta, structures, codes, concrete, steel, masonry, timber, upgrading.
Canadian Journal of Civil Engineering - Tập 17 Số 5 - Trang 813-834 - 1990
Engineering lessons from the 28 September 2018 Indonesian tsunami: debris loading A field survey team went to Palu City, Indonesia in the aftermath of the September 28th, 2018 earthquake and tsunami to investigate its effects on local infrastructure and buildings. The study focused on the coast of Palu Bay, where a tsunami wave between approximately 2 and 7 m high impacted the local community as a result of several complex tsunami source mechanisms. The following study outlines the results, focused on loading caused by debris entrained within the inundating flow. Damage to timber buildings along the coast was widespread, though reinforced concrete structures for the most part survived, providing valuable insights into the type of debris loads and their effects on structures. The results of this survey are placed within the context of Canadian tsunami engineering challenges and are compared to the recently-released ASCE 7 Chapter 6 – Tsunami Loads and Effects, detailing potential research gaps and needs.
Canadian Journal of Civil Engineering - Tập 47 Số 1 - Trang 1-12 - 2020
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