In Ontario, two types of alkali--aggregate reaction exist. Each type is evaluated using different tests. Over the past few years, new tests have been introduced to replace some existing test methods. The new tests are faster and more reliable. Preventive measures such as the use of low-alkali cement and supplementary cementing materials, while they are effective, have not been extensively used with reactive aggregate in Ontario. Beneficiation or selective extraction is used with some potentially reactive aggregates.
Unbalanced moments, transferred between concrete flat plates and columns due to earthquakes, produce shear stresses that increase the vulnerability to brittle punching failure. Appropriate design and detailing of the slab-column joints are essential to prevent such failure. Because of the high flexibility of flat plate structures, lateral-force-resisting systems, e.g., bracings, frames or shear walls, are necessary to limit the interstorey drift ratio to specified values. The slab-column joints must have the strength and the ductility to undergo, without punching failure, the lateral displacement of the structure. In the 2004 version of the Canadian standard, CSA A23.3-04, clause 21.12.3 is added, specifying the punching shear design of slab-column connections subjected to earthquakes. The provisions of the clause are critically reviewed using a design example. It is shown that the new clause permits absence of shear reinforcement in cases that lack strength and when it requires shear reinforcement, it specifies excessive amount. Changes to the standard are proposed.
A simple alternative equation for the calculation of the strength of laterally unbraced structural steel beams is presented herein. This equation uses a format similar to the present steel column design curve in the Canadian structural steel design standard, CAN/CSA-S16-09, and is proposed as a replacement for the existing three part curve for beam strength by a one part equation with a continuous derivative. A reliability analysis of the new equation indicates that the equation provides safety levels very close to those of the current formula for classes 1 and 2 rolled sections. It also provides the desired level of safety for welded beams, whereas the current equations tend to over-estimate their strength. The alternative equation also provides adequate safety for class 3 beams. The concept of maximum unbraced length for braced beam design (Lu) is revisited herein and a simple calculation for this length is also proposed.
During his career as a consulting engineer, Philip Louis Pratley of Montreal, Quebec, was responsible for the design and erection of many of Canada's most outstanding long-span highway bridges. Among them are the Jacques Cartier Bridge (1930) at Montreal; the Ile d'Orleans Bridge (1935) at Quebec City, Quebec; the Lions' Gate Bridge (1938) at Vancouver, British Columbia; the Angus L. Macdonald Bridge (1955) at Halifax, Nova Scotia; and the Burlington Bay Skyway Bridge (1958) at Hamilton, Ontario. For over 40 years Pratley was at the forefront of his profession in Canada in designing and supervising the erection of bridge structures that embodied the latest state-of-the-art advances in design theory, construction technologies, and structural materials; his published technical writings conveyed the latest developments in bridge design and construction practice. Two of his structures; namely, the Jacques Cartier Bridge and the Lions' Gate Bridge, have attained a symbolic importance as national icons. The present article provides an overview of his outstanding career as a bridge design engineer.
Scholars have noted that cross-border businesses have been increasingly using alternative forms of overseas involvement instead of going-it-alone. A study was conducted to document and subsequently identify possible patterns from the strategic joint ventures adopted by selected contractors that appeared in the Engineering News Record's annual top 225 international contractors survey from 1999-2003 inclusively, which was also the framed study period. The modes of strategic joint ventures that became the focus of the study were equity joint venture companies, serial joint ventures, and long-term joint venture contracts. Data was collected entirely from secondary sources, which were triangulated to remove possible biases. The study found patterns in terms of frequency of the various modes, nationality of partners, markets the joint ventures served, and industries the partners belonged to. The findings add to our knowledge on the behaviour of cross-border contractors.
From an engineering application point of view in reducing fugitive particulate matter emissions, this paper presents experimental data comparing the efficiency of woven straw at reducing entrained emissions of particulate matter with diameters less than 10 mu m (PM10) with that for particulate matter with diameters less than 2.5 mu m (PM2.5) at construction sites A series of field-analogous experiments were carried out to continuously measure PM10 in and PM2.5 using laser particle monitors in an artificial wind tunnel system It was found that the efficiency of woven straw at reducing either PM10 or PM2.5 is significantly dependent on the woven straw coverage ratio. The maximum reduction efficiencies for PM10 and PM2.5 are about 40% and 12%. respectively Note that the reduction efficiencies approach zero as the coverage ratio is less than about 40%. Total elimination of PM2.5 and PM10 emissions is not possible, even using full-coverage woven straw. Reduction of PM2.5 emissions is less efficient than that of PM10 In emissions using woven straw, and this trend is likely more obvious with an increase in the woven straw coverage ratio The ratio of reduction efficiencies (R) between PM2.5 and PM10 in for woven straw decreased slightly with an increase in the woven straw coverage ratio. Overall, for wind speeds of 0.5-3.0 m/s. silt contents of 4.8%-21.0%, and soil moisture contents of 10%-30% as used in this work, the average value of R is 0.31. The effects of wind velocity, silt content and moisture content on the reduction efficiencies are also discussed
This paper presents an assessment of the seismic performance of a ductile concrete core wall used as a seismic force resisting system for a 12-storey concrete office building in Montreal, designed according to the 2005 National building code of Canada (NBCC) and the 2004 Canadian Standards Association standard A23.3. The core wall consists of a cantilever wall system in one direction and a coupled wall system in the orthogonal direction. The building is analyzed in the nonlinear regime. The main conclusion from this work is that the capacity design shear envelope for the studied wall structure largely underestimates that predicted, primarily in the cantilever wall direction, and this in turn significantly increases the risk of shear failure. This issue is essentially due to (i) an underestimation by the new NBCC spectral response acceleration of the higher mode responses of a reinforced concrete wall structure whose seismic response is dominated by higher modes; and (H) a deficiency in the capacity design method in estimating the wall shear demand on such walls, even when their behavior is lightly inelastic.
Les tendances climatiques possibles (temperature, precipitations et evapotranspiration potentielle) pour Regina, Saskatchewan, sont decrites; elles sont fondees sur des comparaisons de projections tirees de donnees historiques et des calculs de l'utilisation de quatre modeles de circulation generale (MCG). Les resultats utilises proviennent des modeles de circulation generale CGCM3,1, CCSM3, HadGEM1 et MIROC3,2, en plus d'une serie de synopsis decrivant les relations entre les forces a la base des gaz a effet de serre et les emissions aerosols durant le 21(e) siecle, ce qui demontre les tendances accelerees dans les temperatures et les precipitations. Contrairement aux projections identifiables et divergentes des moyennes de temperatures annuelles, il existe des differences relativement faibles dans les projections de precipitations annuelles en utilisant quelques scenarios d'emissions projetees. De plus, bien que les projections indiquent que des taux de precipitation superieurs sont prevus, ils n'augmenteront pas la disponibilite de l'eau en raison des plus grandes augmentations projetees d'evapotranspiration potentielle; le resultat sera donc une diminution de la disponibilite d'eau au cours du prochain siecle.
The aim of this study is to gain an understanding of the representativeness and relative severity of ASTM C672 and NQ 2621-900 standard test procedures in evaluating the scaling resistance of concrete incorporating various proportions of fly ash (25% and 35%), slag (25% and 35%), and silica fume (1% and 2%). Length of curing and presaturation of samples were varied before starting the freeze-thaw tests. Laboratory durability of tested concrete was compared with that of similar concrete after 4 years of service life. Results show that the length of the moist pretreatment period is a key parameter in scaling resistance of laboratory-tested concrete. A 28-day period of moist curing appears to be optimal and leads to more realistic assessment of the actual scaling resistance of concrete. The use of a draining-bottom mold had no significant effect on the scaling resistance of the concretes in this study.L'étude vise à mieux comprendre la représentativité et la sévérité relative des procédures d'essais normalisées ASTM C672 et NQ 2621-900 pour l'évaluation de la durabilité à l'écaillage de bétons produits avec des liants contenant différentes proportions de cendres volantes (25 % et 35 %), de laitier (25 % et 35 %) et de fumée de silice (1 % et 2 %). Les durés du mûrissement et de la période de présaturation des éprouvettes ont été variées avant le début des essais d'écaillage. La durabilité en laboratoire des bétons testés a été comparée avec celle de bétons similaires après 4 années de service. Les résultats montrent que la durée du prétraitement humide est un paramètre clé de la durabilité à l'écaillage des bétons testés en laboratoire. Un mûrissement humide de 28 jours apparaît optimal et conduit à une estimation plus réaliste de la résistance à l'écaillage réelle des bétons. L'utilisation d'un moule à fond drainant n'a pas d'effet sur la résistance à l'écaillage des bétons de cette étude.
Estimating the amplitude of the average annual flood of small, rarely instrumented watercourses is becoming more and more interesting, especially in a systemic environmental management of a drainage basin. Thirty-seven natural rivers draining less than 360 km2 in the province of Quebec were scaled and the variability of series of annual daily maximums are examined. Based on the results obtained, an empirical regression relationship correlating the average annual flood with the drainage basin is proposed. Key words : average annual flood, scaling, variability, regression, province of Quebec. [Journal translation]L'estimation de l'ampleur de la crue moyenne de petits cours d'eau, rarement instrumentés, prend de plus en plus d'intérêt, notamment dans l'optique d'une gestion environnementale systémique d'un bassin versant. À partir de 37 rivières naturelles drainant moins de 360 km2 et s'écoulant sur le territoire de la province de Québec, la nature de l'échelonnage ainsi que la variabilité des séries de maximums journaliers annuels sont étudiés. Sur la base des résultats obtenus, une relation empirique de régression liant la crue moyenne à l'aire du bassin versant drainé est proposée. Mots-clés : crue moyenne, échelonnage, variabilité, régression, province de Québec.
The discovery of vast quantities of hydrocarbons during exploration of the Mackenzie Delta has led to the detection of numerous anomalous deep holes in various delta channels in the past four decades. The proposed pipeline crossing from the Mackenzie Delta to northern Alberta has renewed interest in studying the stability of these deep holes. The main goal of this research project was to study ice-covered flow velocity and bed shear stress distributions using a previously calibrated computational fluid dynamics (CFD) model for a 30 m deep hole in the East Channel of the Mackenzie Delta to provide an initial assessment of its stability. In this study, a previously developed 3D CFD model using the FLUENT code with the renormalization group theory (RNG) k-epsilon turbulence closure model with nonequilibrium wall functions was adapted to represent ice-covered flow conditions for the study reach. The numerical model was applied to simulate four flow conditions (500, 720, and 1000 m(3)/s along with a moving ice cover during a flow rate of 720 m(3)/s). Results indicated that a single vortex was formed near the inner bend above the hole and deposition may be a key process occurring during ice-covered flow conditions.
The TRANSYT-7F and Synchro models are used in developing optimal timing plans in the city of Al-Khobar, Saudi Arabia. This paper evaluates the adequacy of both TRANSYT-7F and Synchro under local traffic conditions by comparing queue lengths observed along a major arterial in the study area with simulated queues. The models were then calibrated to produce simulated queue lengths which are as close as possible to the observed ones. A clear difference was found between queue lengths estimated by Synchro and TRANSYT-7F. A queue length calibration process was accomplished for TRANSYT-7F by using platoon dispersion factor values of 20 and 35 for through and left-turning traffic, respectively. Synchro calibration was unsatisfactory. The simulated queue lengths could not be calibrated in a meaningful way to resemble the observed queue lengths. Regardless of this, both models produced comparable optimal signal timing plans.
A coupled advanced regional prediction system - community multi-scale air quality (ARPS-CMAQ) modeling system was applied to develop an abatement strategy for air pollutant emission in the Handan region of the northern China The system was evaluated by comparing the simulated concentrations of particulate matter less than 10 mu m (PM(10)) with the observed results in the study area during the four representative months in 2005. A process of planning emission abatement was applied by gradually reducing PM(10) emissions from the original GIS-based emission inventory until a modeling emission scenario was obtained under which the simulated PM(10) concentrations could satisfy the desired air quality objective The air quality objective was represented by ail air quality guideline satisfaction ratio of 80% to reach a dally PM(10) concentration of 150 mu g/m(3) after the year 2010 The modeling system and results could provide sound basis for decision makers to develop an effective air quality management strategy.
Vibration-based damage detection (VBDD) comprises a family of nondestructive testing methods in which changes to signature dynamic characteristics are used to track the condition of a structure. Although VBDD methods have been successfully applied to various mechanical systems and to simple beam-like structures, significant challenges remain in extending this technology to complex, spatially distributed structures such as bridges. In the present study, numerical simulations using a calibrated finite element model were used to investigate the use of VBDD methods to detect small-scale damage on a two-span, integral abutment overpass structure located in Saskatoon, Saskatchewan. Five different VBDD techniques were evaluated, as were the effects of sensor spacing, mode shape normalization, and uncertainty in the measured mode shapes. It was found that localized damage to the top concrete cover of the bridge deck could be reliably detected and located if the sensors were located sufficiently close to the damage and if uncertainty in the mode shapes was attenuated through the use of a sufficient number of repeated trials. Furthermore, preliminary studies indicate that it may be possible to detect damage using sensors that are placed well away from the damaged area.
Existing techniques for microscopic simulation of lane changes utilize a single critical gap for a single vehicle. Freeway merging areas have been among the most difficult aspects of simulations due to the wide variety of merging behaviors in these areas. This paper proposes a gap acceptance model developed to update the size of the critical trailing gap for a merging vehicle during simulation based on the location of the vehicle in an acceleration lane. It also considers the relative speed and critical leading gap. Sets of critical trailing gap values for various situations are computed. The outputs from the microscopic simulations utilizing the proposed model were compared with field data, producing strong statistical evidence that the simulation results and field data were significantly comparable.Les techniques existantes de simulation microscopique des changements de voies utilisent un seul intervalle de sécurité pour un véhicule unique. Les zones de convergence des autoroutes ont été parmi les parties les plus difficiles à simuler en raison de la grande variété de comportements de convergence dans ces zones. Le présent article propose un modèle d'acceptation de l'espacement pour mettre à jour la dimension de l'espacement critique en arrière d'un véhicule en convergence durant une simulation basée sur la localisation du véhicule sur la voie d'accélération. Il considère aussi la vitesse relative et l'espacement critique en avant. Des ensembles de valeurs d'espacements critiques à l'arrière sont calculés pour diverses situations. Les résultats des simulations microscopiques utilisant le modèle proposé ont été comparés aux données de terrain, fournissant une forte preuve statistique que les résultats de simulation et les données de terrain sont très comparables.
The development of highway standard design models involves various assumptions regarding design inputs and the road environment. This paper suggests an improvement to the treatment of uncertainty in design inputs by replacing the current deterministic approach with a reliability-based framework. Reliability theory deals with the propagation of quantified variability in design inputs throughout the design process. In such a framework, each design output corresponds to a theoretical probability of noncompliance to design requirements. These probabilities can be used to assess and compare the a priori safety level associated with various design scenarios. This paper proposes that such a priori safety level of standard design outputs should be consistent and close to a prespecified target level. A set of methods is proposed to determine a target value for design safety. A general framework for calibrating standard design models is presented. To demonstrate the concept, the paper presents an application of the calibration framework to the standard design model of crest vertical curves. Calibrated design charts are constructed to yield a consistent design safety level.
Cable rotation caused by ice accretion was specifically modelled and simulated for this paper. Both ice loads and wind-on-ice loads were taken into account during the modelling, and the quantity for the wind-on-ice loads was obtained by integrating air pressure and air shear along the airflow boundary. Air pressure and air shear were both evaluated through time-dependent airflow computations. Two types of overhead transmission line cables, namely, the Bersimis cable and an overhead ground wire, were examined using the new model, and a number of conclusions were drawn. The validity and reliability of the modelling methods were confirmed by comparing the simulation results with those obtained from experimental measurements.Key words: airflow computation, cable rotation, ice accretion, computer modelling, simulation.La rotation des câbles causée par l'accrétion de glace a été spécifiquement modélisée et simulée dans cet article. Les charges de glace et les charges de vent sur la glace ont été considérées durant la modélisation et les charges de vent sur la glace ont été obtenues en intégrant la pression et le cisaillement de l'air à la limite de l'écoulement de l'air. La pression et le cisaillement de l'air ont été évalués par calculs de l'écoulement de l'air en fonction du temps. Deux types de lignes de transmission aérienne, plus particulièrement le câble Bersimis et un câble de garde aérien, ont été étudiés en utilisant un nouveau modèle et plusieurs conclusions ont été tirées. La validité et la fiabilité des méthodes de modélisation ont été confirmées en comparant les résultats de la simulation avec ceux obtenus par mesures expérimentales.Mots-clés : calcul de l'écoulement de l'air, rotation des câbles, accrétion de glace, modélisation et simulation par ordinateur.[Traduit par la Rédaction]
Humic substances (HS) can be isolated in preparative quantities from low rank coal, peat, and soil. Traditionally, treatment with solutions of NaOH, KOH, or metal salts (K(4)P(2)O(7)) has been used for their isolation. The aim of this article is to study the effectiveness of different technologies in extracting HS from peat as well as the impact of the different extractive technologies on the properties of the isolated HS. Yields of HS depend very much on the extraction process (extractant, temperature, pretreatment procedures, solvent, mixing intensity); however, the properties of the substances obtained (molecular mass, number of functional groups, spectral characteristics) differ significantly. Yields of HS can be associated with the degree of destruction of the peat fibres and intensive destruction technologies provide opportunities to obtain HS from peat in higher yields than traditional extraction methods. However, during the extraction process, significant degradation of the humic molecules takes place.
Corrosion of reinforcement is one of the major causes of deterioration in reinforced concrete structures. Various crack patterns are nucleated around reinforcernent in concrete due to expansion of corrosion products. Crack kinematics of locations, types, and orientations are quantitatively determined by the acoustic emission (AE) - simplified Green's functions for moment tensor analysis (SiGMA) procedure in association with laboratory tests conducted oil concrete specimens simulating corrosion-induced damage. These kinematic outcomes are obtained as three-dimensional (3-D) locations and vectors, and are thus visualized in 3-D by using virtual reality modeling language (VRML). Numerical analysis is conducted by the boundary element method (BEM) based on the concept of linear elastic fracture mechanics (LEFM) to clarify the mechanisms of corrosion-induced crack extension. Relationships between dimensionless stress intensity factors and cracking types are studied by BEM. Contributions of mode I and mode II failures are dependent on the cracking types. It is found that the process of crack propagation due to corrosion of reinforcement in concrete is mostly a mode I fracture with mixed-mode and, in a few cases, mode II fracture.
In recent decades, the need for effective automation of data acquisition and three-dimensional (3D) modeling in the construction industry has been increasing. Most of the 3D modeling methods developed thus far are generally inadequate for construction automation on account of the long processing times involved and the high cost of the devices used for that purpose; moreover, they tend to include a significant level of manual operation. Flash laser distance and ranging (LADAR), which has been developed recently, entails illumination of an entire scene with diffuse laser light. This characteristic enables it to rapidly model actual construction sites in a comparatively fast and cost-effective manner. In this study, flash LADAR technology was tested for its ability to handle the dynamic nature of a construction site in an effective way. Indoor experiments were carried out to characterize the performance of the flash LADAR system, and outdoor experiments were performed on actual construction sites to demonstrate the applicability of the system to 3D modeling of such environments. The results indicate that 3D modeling via flash LADAR has the potential of being quite beneficial for construction automation.
The build-operate-transfer (BOT) scheme is widely applied to finance new infrastructure projects with private sector (concessionaire) participation. For a predetermined concession period (CP), assuming that CP consists of the construction duration (CD) and the concession operation period (OP), different construction durations result in different profits for the concessionaire. Meanwhile, according to the time-cost trade-off (TCT) principle, shortening the CD increases the construction cost; shortening the CD also prolongs the OP, which could increase the total benefit of BOT projects. Hence, how to arrange construction reasonably to maximize the whole profit is a key issue for a concessionary. This paper proposes a methodological framework including optimization, sensitivity analysis, and improved (incentive) genetic algorithms (GA) for BOT projects. Through the proposed methodological framework, the reasonable construction duration of a BOT project can be obtained. A numerical example is used to verify the proposed methodology.
In the present study, the potential of ZnCl2 activated coir pith carbon for adsorption of phenol from aqueous solution was investigated. Batch kinetics and isotherm studies were carried out to evaluate the effects of contact time, initial concentration, adsorbent dose, pH, and temperature. Adsorption kinetics was tested for first order, second order, and Bangham's model and rate constants of kinetic models were evaluated. Equilibrium isotherms for the adsorption of phenol were analysed by Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm models. The Langmuir adsorption capacity, Q(0), was found to be 92.58 mg g(-1) of the adsorbent. pH effect showed that physical adsorption might be involved in the adsorption process. Thermodynamic studies revealed that the adsorption of phenol by activated carbon was an endothermic process. The negative value of Delta G(0) indicated the spontaneity of the adsorption process. Removal of phenol from synthetic wastewater was also tested. This study showed that ZnCl2 activated coir pith carbon could be used as an efficient adsorbent material for the removal of phenol from water.
The flow on urban and suburban freeways is characterized typically by high densities, occupancies, and frequent breakdowns, particularly when the volume approaches capacity. This creates unstable flow conditions, resulting in recurrent as well as random congestion. The purpose of this study was twofold: (1) to develop models for evaluating flow characteristics on a busy suburban freeway, specifically speed versus flow and flow versus Occupancy; (2) to understand the meaning of capacity by evaluating the actual capacity of a freeway section. The data were collected on Highway I in Israel and on Interstate 66 in Virginia, USA. Previous observations showed that both freeways operated at a saturated-flow condition almost daily and that breakdowns of the stream occurred often, though not daily. The paper presents a concept that suggests that freeway capacity is an actual-site specific term. This capacity can change frequently in space and time, depending on the section geometry, the time interval, the prevailing traffic and environmental conditions, and driving behavior. Determination of a representative value of actual capacity for level-of-service or planning analyses is suggested, based on one of three methods: parabolic curve-fitting for free-flow, dense congested stable (DCS) flow, and breakdown-flow data; the intersection of the best-fit stable-flow parabola and the equal-density adjusted line; and curve filling of one-regime models to flow-occupancy data. Also included is a comparison with the 2000 Highway capacity manual (HCM) models and with capacity estimates from other studies. The results showed similar values of actual capacity estimates for the three methods.
In order to ensure safe and comfortable riding, increase network serviceability, and slow pavement deterioration rate, two different strategies are being used simultaneously by transportation departments: routine maintenance and major rehabilitation. Within Alberta Infrastructure, the decision between these alternatives is made based on the pavement condition. Data are collected frequently for the purpose of pavement evaluation. Experienced engineers and technicians normally decide the most appropriate data collection procedure and gauging length associated with it.Key words: pavement, data collection, evaluation, gauging length, condition rating.Afin d'assurer une conduite sécuritaire et confortable, une augmentation de l'état de service du réseau, et un taux de détérioration du pavé plus lent, deux stratégies différentes sont utilisées simultanément soit l'entretien routinier et la réhabilitation majeure. À l'interne d'«Alberta Infrastructure», la décision entre ces deux alternatives est prise selon la condition du pavé. Des données sont collectées fréquemment afin de faire l'évaluation des pavés. Des ingénieurs et des techniciens expérimentés décident normalement de la procédure la plus appropriée afin de faire la collecte des données et de la longeur de calibration correspondante.Mots clés : pavé, collecte de données, évaluation, longueur de calibration, évaluation des conditions.[Traduit par la Rédaction]
This paper presents a detailed experimental investigation of the acid resistance of economical self-compacting concrete (SCC) prepared with natural pozzolan, immersed for up to 12 weeks in sulphuric acid (H(2)SO(4)) and hydrochloric acid (HCl) solutions. The results are compared with those from a control concrete and other SCCs prepared with fly ash and limestone filler. The different factors considered in this study were the effect of mineral admixture type and the strength classes (30, 50, and 70 MPa) of the concrete specimens. In total, 12 formulations were tested. Mass and compressive strength losses are the main properties investigated. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses were used to better understand the kinetics of deterioration of each type of concrete. The results show the positive influence of natural pozzolan on the behaviour of SCC under both sulphuric and hydrochloric acid mediums.
At conditions within the range of those typically applied for commercial drinking water applications, the impact of ultraviolet and hydrogen peroxide (UV/H2O2) advanced oxidation (AO) on the concentration, spectral characteristics, hydrophobicity, and biodegradability of natural organic matter (NOM) in a raw surface water and ultrafiltered surface water was studied. At an initial H2O2 dose of 20 mg L-1, UV/H2O2 mineralized less than 15% of the NOM in raw surface water at a fluence of 1500 mJ cm-2. Natural organic matter in ultrafiltered surface water was mineralized by at least 27% after about 1500 mJ cm-2. Partial oxidation of NOM led to ring opening of aromatic structures, cleavage of conjugated double bonded carbon structures, and reduction in the degree of aromatic substitution. The UV/H2O 2 AO preferentially reacted with hydrophobic fractions of NOM leading to the formation of hydrophilic products. The treatment oxidized recalcitrant NOM into more readily biodegradable compounds with significant increases in formaldehyde and acetaldehyde concentrations. Depending on NOM properties for a given water, UV/H2O2 AO may cause partial oxidation of NOM leading to the formation of biodegradable compounds. The presence of these species may need to be addressed with a downstream process capable of improving biological stability.
In-line addition of alum and ferric chloride was conducted at a hollow-fibre immersed ultrafiltration (UF) membrane pilot plant, using secondary effluent from a municipal wastewater treatment plant (WWTP) as the feed. The objective of such pretreatment was to remove phosphor-us from the feed from an initial concentration of approximately 5 mg/L to below 0.3 mg/L. The simplified in-line coagulant addition process involved hydraulic mixing of the coagulant into the feed and subsequent flocculation, and a greatly reduced (12-14 min) flocculation time relative to conventional coagulation-flocculation-settling treatment. Both alum and ferric chloride effectively removed phosphorus to below the 0.3 mg/L threshold when applied as a pretreatment at optimized doses, both of which were below the WWTP's current coagulant dose (as ferrous chloride). This simplified pre-treatment scheme provided consistent enhanced removal of phosphorus and organic compounds. These results suggest that simplified in-line coagulant addition in advance of immersed UF membranes enhances the ability to produce treated effluent suitable for water-reuse applications.
This paper presents an optimization model for locating changeable message signs (CMSs) on an integrated freeway-arterial network. Compared with existing models, the proposed model represents a well-balanced compromise between Computational efficiency required to solve problems of realistic size, and model realism to ensure the quality of solutions. The model has three unique features: (1) it recognizes that locating CMSs is a planning problem that must take into account both current and future needs and benefits, (2) it evaluates benefits of CMSs over multiple time periods with different traffic distributions, and (3) it explicitly considers inherent variations in incident characteristics across links and over time. A sensitivity analysis is performed to examine the potential impacts on optimal CMSs locations resulting from uncertainties in various input parameters, Such as traffic demand, incident attributes, and driver behaviour. Lastly. the proposed model is applied to the Highway 401 express-col lector freeway system in Toronto for relocating the existing CMSs.
The dynamic modulus (vertical bar E*vertical bar) is one of the primary hot-mix asphalt (HMA) material property inputs at all three hierarchical levels in the new Mechanistic-empirical pavement design guide (MEPDG). The existing vertical bar E*vertical bar prediction models were developed mainly from regression analysis of an vertical bar E*vertical bar database obtained from laboratory testing over many years and, in general, lack the necessary accuracy for making reliable predictions. This paper describes the development of a simplified HMA vertical bar E*vertical bar prediction model employing artificial neural network (ANN) methodology. The intelligent vertical bar E*vertical bar prediction models were developed using the latest comprehensive vertical bar E*vertical bar database that is available to researchers (from National Cooperative Highway Research Program Report 547) containing 7400 data points from 346 HMA mixtures. The ANN model predictions were compared with the Hirsch vertical bar E*vertical bar prediction model, which has a logical structure and a relatively simple prediction model in terms of the number of input parameters needed with respect to the existing vertical bar E*vertical bar models. The ANN-based vertical bar E*vertical bar predictions showed significantly higher accuracy compared with the Hirsch model predictions. The sensitivity of input variables to the ANN model predictions were also examined and discussed.
An overview of cohesive sediment transport processes is given in this paper, and a mass-balance equation that is commonly used to treat cohesive sediment transport is reviewed. The equation highlights transport parameters and processes that are important for modelling the transport of cohesive sediment. The flocculation mechanism that distinguishes cohesive sediment from its noncohesive counterpart is elaborated using a laboratory study that was carried out in a rotating circular flume using sediments from Hay River, Northwest Territories, Canada. A mathematical model of flocculation suitable for predicting flocculation of sediment in rotating circular flumes is reviewed. Other cohesive sediment transport processes such as erosion and deposition processes at the sediment-water interface, entrapment of fines in gravel beds, consolidation, fluid mud, and fluidization due to wave action are reviewed. Additional challenges and knowledge gaps that exist in the area of cohesive sediment transport are identified.
The breakup of the winter ice cover is a brief but seminal event in the regime of northern rivers, and in the life cycle of river and basin ecosystems. Breakup ice jams can cause extreme flood events, with major impacts on riverside communities, aquatic life, infrastructure, navigation, and hydropower generation. Related concerns are underscored by the issue of climate change and the faster warming that is predicted for northern parts of the globe. Advances in knowledge of breakup processes and related topics, achieved over the past 15 years or so, are outlined. They pertain to breakup initiation and ice-jam formation, ice-jam properties and numerical modelling of ice jams, waves generated by ice-jam releases, forecasting and mitigation methods, sediment transport, ecological aspects, and climate-change impacts. Major knowledge gaps are associated with the dynamic interaction of moving ice with the flow and with the stationary ice cover. Increasing computing capacity and remote sensing sophistication are expected to provide effective means for bridging these gaps.
This paper presents a comprehensive review of the work done by a number of researchers on the modeling of asphalt mixture. Included are some of the earliest models such as those with non-interacting particles (models with and without geometry specified), models with particle interaction, and some new models developed in recent years. The paper focuses on the description and comparison of the most recently developed finite element network model (FENM), a clustered discrete element model (DEM), and a micromechanical finite element model (FEM) used in micromechanical modeling of asphalt mixture. These models consider the complex mixture microstructure and aggregate-aggregate interaction. These models are demonstrated and applications of the advances are provided, where virtual laboratory simulation and laboratory tests were employed. The feasibility of nanotechnology application in asphalt mixture is also briefly discussed.
The extent of comparable nitrogen removal in the full- and partial-bed biological aerated reactors needs further microbiological evidence, specifically the existence of ammonia-oxidizing bacteria (AOB). The nitrogen removal process in such systems is typically initiated by chemoliautotrophic ammonia-oxidizing bacteria converting ammonia to nitrite and traces of oxidized nitrogen gases. The formation of a dense biofilm as a result of higher turbulence would account for the higher number of AOB cells enumerated in the biofilm samples from the partial-bed reactor (4.3 × 105 ± 1.9 × 105 No. of AOB cells/mL sample) as compared with those from the full-bed reactor (1.5 × 105 ± 8.0 × 104 No. of AOB cells/mL sample).Il faut plus de preuves microbiologiques pour déterminer et comparer l'étendue de l'élimination de l'azote dans les réacteurs biologiques aérés avec lit complet et partiel, plus particulièrement en ce qui a trait à l'existence des bactéries oxydant l'ammoniac (« AOB »). Le processus d'élimination de l'azote de tels systèmes est normalement initié par la conversion de l'ammoniac en nitrites et en traces de gaz d'azote oxydé par les bactéries autotrophes oxydant l'ammoniac. La formation d'un biofilm dense découlant d'une turbulence supérieure dans le réacteur à lit partiel pourrait justifier le plus grand nombre de cellules AOB comptées dans les échantillons de biofilm (4,3 × 105 ± 1,9 × 105 cellules AOB/mL d'échantillon) provenant de ce réacteur par rapport à celles trouvées dans le réacteur à lit complet (1,5 × 105 ± 8,0 × 104 cellules AOB/mL d'échantillon)
The effect of jet aeration on the mean hydrodynamic forces applied on plunge pool floors was investigated. A mathematical expression is proposed to estimate the buoyancy coefficient reflecting the aeration effect, including contributions from previous authors. A correction of the theoretical values resulting from this expression based on data obtained in an experimental setup with vertical submerged rectangular (two-dimensional) aerated jets is proposed. The effect of the buoyancy coefficient is introduced in the integration of the hydrodynamic pressures over slabs of the plunge pool floor. Dimensionless forces on the upper faces of the slabs are determined for different air concentrations of the impinging jet. The effect of jet aeration entering the plunge pool on the uplift force applied in the lower faces of the slabs in the case where a waterstop failure occurs is also analysed.L'effet de jets d'aération sur les forces hydrodynamiques moyennes appliquées sur les planchers de bassins a été examiné. Une équation est proposée pour estimer le coefficient de flottaison reflétant l'effet d'aération, incluant les contributions d'auteurs précédents. Une correction des valeurs théoriques découlant de cette équation basée sur des données obtenues lors d'une expérience en laboratoire avec des jets d'aération rectangulaires (bidimensionnels) verticaux submergés est proposée. L'effet du coefficient de flottaison est introduit dans l'intégration des pressions hydrodynamiques exercées sur les dalles du plancher des bassins. Les forces sans dimension aux faces supérieures des dalles sont déterminées pour différentes concentrations d'air dans le jet incident. L'effet du jet d'aération entrant dans le bassin sur la force ascendante appliquée aux faces inférieures des dalles est également analysé dans le cas d'une défaillance de joint d'étanchéité.
A field trial involving 50 separate releases of inert aerosol (kaolin) was conducted to determine the concentration distribution within aerosol puffs resulting from near-instantaneous releases. Atmospheric conditions during the trial fell within Pasquill stability classes A and B (very and moderately unstable, respectively). Aerosol concentration measurements were made using a scanning lidar system operating at 1.06 mu m. Artificial neural network (ANN) models were developed using the data to predict concentration distributions, given a number of meteorological parameters. The ANN predictions were compared to those from traditional Gaussian puff models, and provided better predictions than the Gaussian model parameterizations examined. The ANN models were also used to develop Gaussian fitting parameters to replace traditional Pasquill and Slade dispersion coefficients. The ANN-derived dispersion coefficients provided better predictions of measured puff concentration distributions than either the Pasquill or Slade parameterizations, though the full multi-input ANN models provided even better predictions than the Gaussian puff model using ANN-derived dispersion coefficients.
In part I, relationships were obtained in the laboratory between the expansion due to alkali-silica reaction (ASR) and (i) the "stiffness damage test" (SDT), (ii) the "damage rating index" (DRI), and (iii) the surface cracking of the concrete. These tests were conducted on nonreinforced concrete blocks and cylinders made with various reactive aggregates and stored at 38 °C and >95% relative humidity. The objective of part II was to verify the validity of the relationships from part I for concrete elements made in the laboratory but exposed outside. On average for the 51 blocks and 14 slabs tested, the surface cracking increased with ASR expansion and approached the measured expansion in the case of the most severely exposed sections of the specimens tested. The ratio between the expansion estimated from the surface cracking and the measured expansion varied greatly from one specimen to another (between 0 and 4.3), however. Taking into account the type of reactive aggregate involved did not explain the situation. Despite a variety of reactive aggregates, a quite good relationship (coefficient of linear regression R2 = 0.89) was obtained between the DRI and the ASR expansion for the six blocks cored and tested for DRI and SDT. This relationship is significantly different from those obtained in the laboratory, however. Moreover, the exposed concretes clearly differ from the laboratory concretes regarding the most important defects observed in the DRI test. As in the laboratory, the results obtained from the SDT seem to depend on the type of reactive aggregate involved. Nevertheless, this test globally supplied results with the best agreement with the measured expansion.
Plusieurs facteurs peuvent affecter la productivite de la main-d'oeuvre, mais la constructibilite est l'une des plus importants. Une recherche bibliographique en profondeur a toutefois revele un grand manque de recherche de l'effet de la constructibilite sur la productivite de la main-d'oeuvre lors de la construction en beton arme sur place. La presente recherche porte donc sur la quantification des effets et l'influence relative de la variabilite des dimensions des poutres, de la repetition du plan d'etage, la superficie du plancher, la surface moyenne des dalles, l'intersection des poutres, le rapport poutre-plancher et les pourcentages de poutres courbes et de dalles non rectangulaires sur la productivite de la main-d'oeuvre de coffrage des planchers des batiments. Les facteurs de constructibilite examines, outre la variabilite des dimensions des poutres, ont des effets importants sur la productivite de la main-d'oeuvre de coffrage et confirment l'importance d'utiliser les concepts de rationalisation, de normalisation et de repetition lors de l'etape de conception des projets de construction. Les resultats peuvent etre utilises pour fournir une retroaction aux concepteurs leur indiquant a quel degre leurs conceptions considerent les exigences des principes de constructibilite ainsi que les consequences de leurs decisions sur l'efficacite de la main-d'oeuvre lors de l'operation de coffrage. D'un autre cote, les profils detectes dans les resultats pourraient guider les directeurs de construction afin qu'ils planifient les activites de maniere plus efficace et utilisent la main-d'oeuvre de maniere plus rationnelle.
The aim of this paper is to present the basic premises of modelling road pricing with an engineering perspective at aggregate and disaggregate levels. An engineering perspective is different than economic perspective according to its analytical and deterministic approach. In this paper most of the economic notions are deliberately simplified, especially at the aggregate level, to obtain a simple, easy to understand, and easy to run model. The paper also includes facts about basic theories of road pricing and economic modelling. To demonstrate the modelling approaches presented in this paper, a simple numerical example is assessed. The results show that aggregate analysis provides understanding of the extent of the impacts whereas disaggregate analysis offers more detailed information. Furthermore, analysis at both levels has the potential to perform a combined modelling study as well.Cet article présente les prémisses de base de la modélisation de l'établissement du prix des routes du point de vue de l'ingénierie respectivement à un niveau global et détaillé. Le point de vue de l'ingénierie est différent du point de vue économique selon son approche analytique et déterministe. Dans cet article, la majorité des notions économiques sont simplifiées délibérément, particulièrement au niveau global, afin d'obtenir un modèle simple, facile à comprendre et à exécuter. Cet article comprend également des faits sur les théories de base de l'établissement des prix et la modélisation économique. Un exemple numérique simple est évalué afin de démontrer les approches de modélisation présentées dans cet article. Les résultats montrent que l'analyse globale permet de comprendre l'étendue des impacts alors que l'analyse détaillée offre une information plus détaillée. De plus, l'analyse aux deux niveaux pourrait aussi permettre de réaliser une étude de modélisation combinée.
La presente etude examine l'influence de la dimension des agregats sur les proprietes mecaniques et de transport du beton et des mortiers de beton equivalent. Un melange de beton a ete dose en utilisant un rapport eau-ciment de 0,45 et un contenu en beton de 450 km/m(3) avec des agregats dont la taille maximale etait de 22,4 mm. Puis, en conservant constant la surface totale des agregats, trois melanges ont ete doses avec le meme rapport eau-ciment mais la dimension maximale des agregats avait diminue de 16 mm, 8 mm et 4 mm en utilisant la methode de mortiers de beton equivalent. Des essais sur les proprietes mecaniques, comprenant la resistance en compression et la resistance a la traction par fendage et les proprietes de transport incluant la permeabilite rapide aux ions chlore, le taux de sorption d'eau, l'absorption d'eau et des essais de permeabilite a l'eau ont ete realises a 7 et a 28 jours. Les resultats des essais indiquent qu'une diminution de la dimension maximale des agregats a augmente la permeabilite a l'eau, la permeabilite rapide aux ions chlore et les valeurs d'absorption et de sorption de l'eau. Toutefois, cette diminution a reduit la resistance en compression et la resistance a la traction par fendage du beton et des mortiers de beton equivalent.
There are three major steel-manufacturing factories in Jordan. All of their by-product, steel slag, is dumped randomly in open areas, causing many environmentally hazardous problems. This research was intended to study the effectiveness of using steel slag aggregate (SSA) in improving the engineering properties of locally produced asphalt concrete (AC) mixes. The research started by evaluating the toxicity and chemical and physical properties of the steel slag. Then 0%, 25%, 50%, 75%, and 100% of the limestone coarse aggregate in the AC mixes was replaced by SSA. The effectiveness of the SSA was judged by the improvement in indirect tensile strength, resilient modulus, rutting resistance, fatigue life, creep modulus, and stripping resistance of the AC samples. It was found that replacing up to 75% of the limestone coarse aggregate by SSA improved the mechanical properties of the AC mixes. The results also showed that the 25% replacement was the optimal replacement level.
The behavior of asphalt mixtures is very complicated due to structural configuration and interfacial friction of aggregates as well as chemical and rheological reactions of the asphalt binder itself or with the aggregates. Furthermore, this complex response is more complicated under various loads, temperatures, and other environmental factors, To control the complex responses and reduce the complex factors, a DSR moisture damage test using small rock disks was developed. This paper focuses on the more fundamental concepts to explain asphalt and asphalt-aggregate bond behavior exhibited under the newly-developed DSR moisture damage test. The traditional model of asphalt structure is based on the theory of colloid and surface chemistry. Although this traditional model can explain many physical phenomena of asphalt structure, it cannot explain all the asphalt behaviors, such as steric hardening. Therefore, more general, but fundamental concepts may be required to attain insight of the material. As one of the possible concepts, a self-assembly concept in supramolecular chemistry is proposed and phenomena and results of the DSR moisture damage test are explained by the concept.
As aggregates recycled from various types of construction waste are continuously being produced, interest has focused on how to apply them for use in highway pavement. This paper considers the application of waste aggregates to lean concrete, based on basic mechanical property tests and environmental toxicity. Compared with natural aggregates, waste aggregates derived mainly from recycled concrete have low specific gravity and high water absorption characteristics. After testing their environmental toxicity, it was found that waste aggregates do not release any metallic ions when introduced to alkaline conditions but do release a small but seemingly harmless amount of metallic ions when introduced to acidic solutions. Concrete made with waste aggregates has significant limitations in strength, particularly flexural strength, which is the main parameter of quality control and design for concrete pavement. It is therefore not practical to use waste aggregates for the surface layer of concrete without using additives or special treatments. It is possible, however, to apply concrete with waste aggregates for lean bases. In testing, lumps of asphalt, cement paste, bricks, and glass were classified as impurities and were observed for changes in strength based on the percentage of impurities used. If the amount of impurities is greater than 25%, the 7-d compressive strength does not meet the strength requirements specified for lean concrete.
The fine granular structure and surface activity of clay minerals increase the amount of mixing water needed to provide workability in concrete. Even when the microfine material percentage in fine aggregate is low, the methylene blue value of the fine aggregate increases when materials of clay origin are present. In this study, methylene blue values were determined in fine aggregate samples used to produce ready-mixed concrete. Samples were taken from four different aggregate quarries, and relationships between methylene blue values of the concrete samples produced with these aggregates and some of their properties were investigated. Tests were done to determine the quality of microfine material (i.e., passing 0.063 mm sieve). Slump, ultrasonic pulse velocity, compressive strength, and surface abrasion resistance tests were performed on concretes made with these aggregate fines. It is shown that clay content, as indicated by the methylene blue value test, affects the concrete properties, but the microfine material percentage does not give any hint about clay content.
Prototypes of columns were cast with different percentages of rebars and stirrups and various alkali-silica reactive aggregates. The deformations of concrete were measured along the three directions using surface metal studs and internal vibrating wire gauges. The deformations of steel were measured using fiber-optic gauges and short rods welded to rebars and stirrups. Along each direction, the deformations of concrete and steel were quite similar up to 0.08% longitudinal expansion, beyond which the rebars were generally showing less ( longitudinal) expansion than concrete. The rebars reduced the longitudinal expansion; the higher the percentage of longitudinal steel, the higher this reduction. On the other hand, the expansion increased in the other two transverse directions to give comparable volumetric expansions for all specimens of the same mixture, with or without relatively spaced-out stirrups. The transverse expansion perpendicular to the casting plane was always higher than the transverse expansion parallel to this plane. The rebars were tensioned up to 280 MPa. The concrete was prestressed parallel to the rebars, up to 3.3 MPa. For their part, the stirrups were highly stressed in tension and flexure, and usually reached plastification.
This study investigates the effects of lightweight aggregates (LWAs) on heat and degree of hydration in high-strength cementitious materials, in which natural pumice LWAs were used as water reservoirs to provide internal curing for mitigating autogenous deformation. Normal aggregates were substituted by LWAs at three different volume fractions, such as 8%, 16%, and 24% of total volume of mortars. The results show that as the amount of LWAs increased, the autogenous deformation significantly decreased, while the heat of hydration increased slightly. The cement particles can easily find water released from LWAs and consequently, the degree of hydration increased due to internal curing. The addition of LWAs caused a delay in the time to approximately reach the asymptotic value of the nonevaporable water content.Cette étude examine les effets des agrégats légers sur la chaleur et le degré d'hydratation dans les liants hydrauliques à haute résistance, dans lesquels des agrégats légers de pierre ponce naturelle ont été utilisés en tant que réservoirs d'eau afin de permettre une cure interne et ainsi atténuer la déformation autogène. Les agrégats normaux ont été remplacés par des agrégats légers selon trois proportions de volume, 8 %, 16 %, et 24 %, par rapport au volume total de mortier. Les résultats ont montré que la déformation autogène diminue grandement en fonction de l'augmentation de la quantité d'agrégats légers, alors que la chaleur d'hydratation augmente légèrement. Les particules de ciment peuvent facilement trouver l'eau libérée par les agrégats légers, permettant ainsi l'augmentation du niveau d'hydratation en raison de la cure interne. L'ajout d'agrégats légers engendre un retard dans le temps approximatif requis pour atteindre la valeur asymptotique du contenu en eau non évaporable.
This paper presents a limited study that characterizes the recycling of artificially aged crumb-rubber modified (CRM) mixtures depending on their recycling percentage and aggregate type. Eight mixtures [six recycled mixtures containing rubberized reclaimed asphalt pavement (RAP) and two control virgin mixtures] were designed and tested. Two types of aggregates were used in this research project. The rubberized RAP used in the study was artificially aged in the laboratory using an accelerated aging processes. The percentages of the RAP, by total weight of the mix, incorporated into the recycled mixtures were 15%, 25%, and 35%. Evaluation of all mixtures included the following testing procedures: tensile strength ratio (TSR), asphalt pavement analyzer (APA), resilient modulus, and indirect tensile strength (ITS) after long-term oven aging. The results from this study showed that (i) the recycled aged CRM mixtures (with 15%, 25%, and 35% rubberized RAP) can satisfy the current Superpave mixture requirements, including moisture susceptibility and rutting resistance, and (ii) in general, there was no significant difference between the control and the recycled CRM mixtures for the properties evaluated in this study.
The Manning formula and the tractive force equation are combined and written in terms of dimensionless parameters. Predetermined solutions to this equation have been obtained and presented in chart form. Also, a mathematical expression is obtained that approximates the chart to determine the channel width explicitly.Key words: open channel, design, tractive force, erodible, shear stress.La formule de Manning et l'équation de la force de traction sont combinées et écrites sous un format avec paramètres adimensionnels. Des solutions prédéterminées ont été obtenues à partir de l'équation combinée et sont présentées sous forme graphique. Une expression mathématique fournissant une approximation du graphique est aussi obtenue afin de déterminer explicitement la largeur du canal.Mots clés : canal à surface libre, conception, force de traction, érodable, contrainte de cisaillement.[Traduit par la Rédaction]
The purpose of this study is to investigate pressurized pipelines and the potential effects on pressure transients of air entrained at the downstream end of large entrapped air pockets followed by a hydraulic jump in pressurized pipelines. The homogeneous two-phase flow model is used to simulate the transient response of the bubbly mixture after a pump shutdown. The results show that pressure transients are significantly reduced with increasing air-pocket volumes and bubbly flow air content. Experimental investigations were carried out to analyze the impact of different air-pocket volumes located at high points of pressurized pipelines. A case study of an existing pumping system was considered to exemplify the impact of the bubbly flow air content on hydraulic transients.Le but de la présente étude est d'examiner les effets potentiels sur les transitoires de pression de l'air entraîné à l'extrémité aval de larges poches d'air emprisonnées suivies d'un saut hydraulique dans les pipelines pressurisés. Le modèle d'écoulement homogène à deux phases est utilisé pour simuler la réponse transitoire du mélange à bulles après l'arrêt d'une pompe. Les résultats montrent que l'augmentation du volumes des poches d'air et du contenu en air de l'écoulement à bulles réduisent de beaucoup les transitoires de pression. Des études expérimentales ont été réalisées afin d'analyser l'impact de différents volumes de poches d'air situées aux points élevés des pipelines pressurisés. Une étude de cas d'un système de pompage existant sert d'exemple pour l'impact du contenu en air de l'écoulement à bulles sur les transitoires hydrauliques.
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.
Air polluted with methanol vapours was treated in a biofilter and a biotrickling filter, both packed with inert materials. The effects of the nitrogen concentration present in the nutrient solution, the empty bed residence time, and the methanol inlet load, on the biofilter and biotrickling filter performance were all examined and compared. The elimination capacity, the biomass and the carbon dioxide production rates all increased with the increase of the parameters tested. The maximum elimination capacity for the biotrickling filter was 240 g·m-3·h-1 with corresponding removal efficiency of 75% and carbon dioxide production rate of 10 g·m-3·h-1, whereas the maximum elimination capacity for the biofilter was 80 g·m-3·h-1 with corresponding removal efficiency of 35% and carbon dioxide production rate of 70 g·m-3·h-1. The biomass production rate was similar for both the biofilter and the biotrickling filter. The carbon dioxide production rate was higher by a factor of 2 to 9 for the biofilter compared to the biotrickling filter.