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Over 50 years ago, a marine estuary was converted to a wastewater stabilization basin for treatment of primarily pulp and paper effluent. As a result, the basin was immediately converted to a “freshwater” environment and subsequently accumulated a thin layer of black, organic-rich sediment containing varying amounts of dioxins and furans, metals, polycyclic aromatic hydrocarbons, and petroleum hydrocarbons. Previous studies on the site have shown that the majority of this contamination in the basin appears to have been contained within this black sediment layer and not migrated to any significant extent into the original underlying marine sediments. The purpose of this study is to examine sediment porewater chemistry changes that have occurred over 51 years of operation of the stabilization basin with the intent of better understanding why contamination has been minimal into the underlying natural marine sediments. Field and laboratory testing is presented to characterize the physical, chemical, and mineralogical sediments in the basin. Porewater chemistry profiles obtained from this work are then used in combination with a one-dimensional contaminant transport model to examine the role of diffusion, sorption, and upward groundwater flux in the porewater profiles found for the sediments.

Cryptococcus albidus , isolated from the sediments of Century Pulp and Paper Mill, Lalkuan, Nainital, Uttarakhand, India, produced a copper containing oxidase, laccase, that was capable of degrading environmental pollutants. Bagasse was the most efficient inducer for laccase production. The Taguchi approach was used to optimize the growth media for five factors, i.e., pH, copper sulphate, carbon, nitrogen, and the inducer at four levels using an M-16 orthogonal array. The optimum conditions for laccase production were pH (6), CuSO4(2 mmol/L), meat peptone (0.5%), glucose (0.1%), and bagasse (1.0%). After optimization, laccase production increased seven times from 32 to 219 IU/mg. The inducer (bagasse) had maximum effect on laccase production leading to 52% increase, while pH had minimum effect with 7% increase. Growth media with laccase activity (2 U/mL) was applied for the bioremediation of dyes, effluent, and chemical compounds. These experiments showed that the growth media with laccase activity (2 U/mL) produced by Cryptococcus albidus had good potential for bioremediation of toxic and recalcitrant compounds. Further, the laccase enzyme extracted from the growth media was fractionated by DEAE-cellulose ion-exchange chromatography, and the molecular weight of the enzyme determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS–PAGE) was found to be 64 kDa. The activity of laccase was confirmed by native PAGE, in which ABTS was used for staining gel.

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.

Acid mine drainage can be curbed or reduced significantly by covering tailings sites with an oxygen barrier. In this study, the ability of pulp and paper residues, more specifically deinking residues, to function as such a barrier was investigated. Field data from two sites show that O2 diffusion through the barriers can be greatly reduced. To better understand how oxygen migrates through deinking residues and to develop prediction tools for future design with deinking residues, one-dimensional effective diffusion coefficients (De) were determined by fitting laboratory experimental curves (O2 concentration versus time data) to curves obtained from computer simulations. The results obtained confirmed the behaviour observed in soil covers: the effective diffusion coefficients are highly dependent on the degree of saturation (Sr) of the compacted material. The De values obtained in this study compare well with those published in the literature for several materials compacted at similar Sr. The De values varied from 8.3 × 10-9 m2/s (Sr approximately 91%) to 9.7 × 10-7 m2/s (Sr approximately 76%). The O2 consumption by biodegradation appears to be an important factor in the reduction of the O2 flux that can reach the bottom of the barrier.Key words: oxygen diffusion, pulp and paper residues, barrier, acid mine drainage.

A major concern in the design of landfill covers and liners that use compacted clays as the hydraulic barrier is freezing and thawing. Paper mill sludges have been used in landfill covers to subtitute for clays as the hydraulic barrier. In this study, laboratory-compacted paper sludges have been subjected to one-dimensional and three-dimensional laboratory freezing and thawing cycles. Freezing and thawing increased the hydraulic conductivity of the paper sludges about one to two orders of magnitude. To determine why freezing and thawing cause an increase in hydraulic conductivity, an evaluation of the effects of freezing and thawing on the macrostucture of paper sludges was conducted. Frozen thin sections of paper sludges were prepared after freeze–thaw cycling and were compared to frozen thin sections of a compacted clay. Macrostructure analysis of the paper sludge and clay thin sections was conducted by using back lighting to reveal the details of ice structure. Analysis of the clay thin sections revealed ice lenses and shrinkage cracks. Ice lenses and shrinkage cracks in sludge thin sections were difficult to determine when the same procedure for compacted clays was used. Key words: freeze, paper sludge, landfill, permeability, macrostructure, thin sections.

The authors have presented an interesting paper on the use of deinking residues to create an oxygen barrier. The paper includes some results from laboratory tests, which can be difficult to perform, and an interpretation based on Fick’s laws solutions. Although the writers, like other researchers active in this field, have expressed some reservations regarding the placement of organic cover materials on reactive (acid producing) tailings (as opposed to inorganic materials such as soils and non-acid generating tailings), it is nevertheless recognized that the proposed approach for controlling the production of acid mine drainage (AMD) is certainly worth investigating. Covers made with deinking residues may eventually be added to the few control methods available for mine operators faced with the prospect of dealing with sulfidic mine and milling wastes. In the following paragraphs, the writers would like to discuss some issues relevant to the problem at hand, including some comments and questions for the authors and interested readers. Air versus equivalent porosity

Construction projects are usually labour intensive, and human resource (HR) issues contribute significantly to a project’s final costs. From this perspective, a tool that can help construction managers reduce their HR costs can potentially generate improvement in the project cost. In this paper we propose a simulation-based approach that sheds light on the dynamics of workforce skill evolution as the project progresses, thereby assisting construction managers in adjusting their HR policies. The proposed approach uses a system dynamics (SD) simulation model that dynamically tracks the effects of alternative HR policies. After the development and validation of the SD model, the SD model is extended to capture operational details and their interaction with workforce skill evolution, adopting a hybrid SD and discrete event simulation (DES). The hybrid model has been applied to an experimental case of structural steel fabrication projects, in which we demonstrate that there is a considerable room for cost-saving in HR. The hybrid modeling approach introduced in this paper can be employed by construction managers for possible improvements in HR management, as well as researchers for an in-depth understanding of the dynamics in workforce skill evolution.

Contractor default is one of the major risks that threaten a project’s success in the construction industry. Previous studies have focused mainly on evaluation of the contractor’s financial aspects to predict contractor default. There remains a need for a comprehensive model that has the ability to incorporate the evaluation of all the project aspects, project team, contractual risks, and project management evaluation criteria to predict the possibility of a contractor’s default on a specific construction project. This paper presents a contractor default prediction model (CDPM) from the surety bonding perspective that incorporates these criteria and uses a fuzzy inference system for reasoning. The CDPM provides a more objective, structured, and comprehensive approach for contractor default prediction for surety practitioners, project owners, and for self-assessment by contractors to reduce the risk of contractor default. The multi-attribute utility function was used to develop a group consensus system (GCS) to aggregate the participating experts’ opinions to build the CDPM. The accuracy of the GCS was found to be 91.1%. A novel approach for fuzzy rule base development is applied to develop the rule base for the CDPM. The CDPM was validated using 30 contractor default prediction cases, and the accuracy was found to be 86.5%.

To improve construction productivity and performance, it must be measured. The Construction Sector Council (CSC) has started a Labour Productivity and Project Performance Benchmarking Program for the infrastructure sector of the construction industry in Canada. Metrics were developed for project cost, time, safety, and quality performance; labour productivity; rework; project conditions; and management practices related to health and safety. Data from 19 projects located in different regions of Canada were collected and analyzed. Based on the results and on industry feedback, additional metrics for practices related to project planning, materials management, and construction supervisory skills development were developed. This paper describes the development of the program. Lessons learned during the development and implementation of the benchmarking and metrics program are summarized and steps to establish a sustainable program are identified. It is concluded that a successful program is feasible and has the potential to have broad impact.

This paper presents a framework for optimizing condition assessment policies by balancing the revealed value of information with the cost of obtaining such information. The computational platform is based on augmenting the asset condition state with an expected level of accuracy. Inaccuracies due to condition assessment reliability are evaluated using the partially observable Markov decision process. The single objective genetic algorithm is used to select the most cost-effective assets to assess considering information inaccuracy under a fixed budget. The model is extended using multiobjective genetic algorithms and fuzzy set theory to include minimizing the risk exposure based on asset consequence of failure. This methodology takes into consideration direct and indirect costs of sudden infrastructure failure and reduced level of service costs. A case study is presented using the City of Hamilton, Canada, water network to demonstrate the capabilities of the model.

The factory-based modular construction process has proven to increase the speed of construction, and improve quality and safety, while providing value to the customer and a rapid return on investment to the builder and owner. However, onsite module assembly creates new schedule demands, as activities are scheduled on a minute-by-minute basis; therefore simulation of the process becomes essential at early stages of a project. Although simulation proves to be an effective tool for project engineers to assess complex construction operations, it remains a symbolic base model with no visual link to the actual physical shape and look of the project’s activities. This paper presents the application of integrated simulation and post simulation visualization as a tool to assist the modular construction industry in scheduling onsite installation of prefabricated modules. The proposed methodology uses simulation model output as an ASCII file in a binary format and imports this ASCII file to 3D Studio Max to perform the animation. The output from the high level simulation model is transformed into frames/second in 3D Studio Max. The proposed methodology was tested on the planned construction of a 34-storey building in Brooklyn, New York, USA. Simulation visualization of the process proved to be effective in communicating the value and simplicity of a minute-by-minute schedule. Based on the output information, the most efficient solutions were generated. The use of post simulation visualization was effective in analyzing the construction methods of the case study which consisted of 950 structural steel modules. Issues related to construction activities’ productivity were synchronized to achieve onsite installation of the project in only 56 working days.

This paper presents an automated method for estimating productivity of earthmoving operations in near-real-time. The developed method utilizes Global Positioning System (GPS) and Google Earth to extract the data needed to perform the estimation process. A GPS device is mounted on a hauling unit to capture the spatial data along designated hauling roads for the project. The variations in the captured cycle times were used to model the uncertainty associated with the operation involved. This was carried out by automated classification, data fitting, and computer simulation. The automated classification is applied through a spreadsheet application that classifies GPS data and identifies, accordingly, durations of different activities in each cycle using spatial coordinates and directions captured by GPS and recorded on its receiver. The data fitting was carried out using commercially available software to generate the probability distribution functions used in the simulation software “Extend V.6”. The simulation was utilized to balance the production of an excavator with that of the hauling units. A spreadsheet application was developed to perform the calculations. An example of an actual project was analyzed to demonstrate the use of the developed method and illustrates its essential features. The analyzed case study demonstrates how the proposed method can assist project managers in taking corrective actions based on the near-real-time actual data captured and processed to estimate productivity of the operations involved.

The critical path method (CPM) has been useful for project planning, yet its float calculation errors in cases of complex schedules hinders its ability to provide decision supports during project control, namely corrective actions and forensic analysis of schedules. To improve project control, this paper enhances the critical path segments (CPS) scheduling technique and incorporates a rich visualization of all as-built events made by all parties, including work stops, accelerations, and rework. Its improved critical path calculation incorporates the decision variables used at the project control stage such as revised construction methods. It also uses a modified float calculation with forward-pass only to avoid float errors. A case study is used to demonstrate the proposed technique and its benefits for project control. This research has the potential to revolutionize scheduling computations to resolve CPM drawbacks and provide decision support capabilities to help improve project planning and control.

Information exchange processes (referred to as transactions) in the AEC/FM (architecture, engineering, construction and facility management) industry are mostly manual and performed on an ad hoc basis. There is a growing trend towards computer-based exchange of information. This allows for more extensive, rapid, and error-free exchange of information, but it requires more formal specifications and agreements to govern these data exchanges. This research focuses on the development of an ontology-supported protocol for formalizing these data exchanges. As part of the development effort, this paper describes a taxonomy of transactions and messages. The knowledge represented in the ontology is evaluated and potential areas of application of the ontology are identified using an industry IT survey.

Although the current economic downturn has eased the stress of broad skilled labour shortages, it is reasonable to believe that the shortage will return when the U.S. economy rebounds. The shortage could become more substantial because the U.S. construction industry is poised to make a significant demographic shift with Baby Boomer workers approaching retirement and Generation Y workers joining the workforce. This paper investigates how different generations of craft workers perceive the factors affecting labour productivity. The data was collected through a survey of 1996 craft workers on 28 U.S. construction sites in 2004 and 2005. The analysis results reveal that: (1) Generation Y, Generation X, and Baby Boomers actually have consensus on the relative impact of productivity factors; and (2) significant differences were also observed on individual productivity factors and the primary differences among the generations were associated with tools and consumables, labour, engineering drawing management, and project policy.

Pipe-works are among the most complicated items to be tracked in the course of monitoring construction project progress. Traditionally, the tracking of pipe-works progress is conducted either manually or using laser scanning technology. While laser scanning is a 3D imaging technique, and commercial software exists to construct 3D CAD models of piping based on such images, it suffers from portability, purchase cost, and other disadvantages. This paper describes digital photogrammetry technology as an alternative for pipe-works reconstruction and as a cost effective tracking tool. For validation, data was collected using a handheld digital camera to acquire images inside a new building under construction. Progress of the pipe-work networks of different types and sizes in the new building was monitored during the construction phases. In addition to the known accuracy and robustness of photogrammetry, it was found that the use of digital photogrammetry provided a practical and low-cost approach.

The state-of-the-art tracking technologies, such as the global positioning system (GPS) and the radio frequency identification (RFID), lend themselves well to applications in relatively open areas, while falling short of accuracy and reliability in indoor or partially covered application settings due to signal blockage, distortion or deterioration. This research aims to address this challenge in construction engineering by exploring a cost-effective positioning methodology to realize automated and continuous tracking of construction resources. The emerging ZigBee-based wireless sensor networks (WSN) technology is introduced. A framework of WSN application is proposed for indoor construction resources tracking, which consists of a group of stationary and mobile sensor nodes that can communicate with one another. Real-time locations of the mobile nodes can be determined by applying the localization method based on received signal strength indicator (RSSI) and geometric trilateration.

Efforts to break down decision-making silos in the architecture, engineering, and construction (AEC) industry have resulted in the evolution of integrated project delivery (IPD). IPD brings together participants to make decisions early in the project cycle. But, anecdotal evidence indicates that IPD is not being implemented as effectively as envisioned. One potential barrier to implementation is the multi-party risk and reward agreement that is a hallmark of IPD. Many owners may be statutorily prohibited from entering into such a risk-sharing contractual arrangement, and countless other organizations “remain skeptical of its practicality.” However, recent case study research established an important link between reimbursable contracting strategies and greater collaboration and information-sharing among parties. The researchers found that more traditional contracting approaches, when combined with a cost reimbursable compensation structure, achieved positive outcomes by properly allocating risk, fostering teamwork, and bringing together diverse experts to address challenging design problems, thus providing a viable alternative to shared risk and reward approaches.

The state-of-the-art of sediment source identification is reviewed in this paper. Sediment “fingerprinting” techniques using different “fingerprint” properties were examined. With these techniques, it is possible to identify potential sources of sediment transported in river systems. Such knowledge is useful for implementing sediment control strategies to limit sediment production from upland areas in a watershed as well as for developing guidelines for land use practices to minimize adverse impacts on surface and ground water resources in agricultural watersheds. Examples of sediment source identification techniques that were carried out in agricultural watersheds in different parts of the world were also included in the present review.

Inertia effects are seldom considered in morphological modeling, and most of the transport models were developed from laboratory experiments in steady uniform flow conditions. This paper considers first the hysteresis effects in transient flows between discharge, velocity, and bottom shear stress. These effects can be taken into account as far as the complete shallow-water equations are used. Secondly, inertia effects linked to the sediment response to acting forces are considered. Three types of models are investigated: (i) sediment movement instantaneously adapting to hydrodynamic changes, (ii) spatial or temporal lag laws to give space or time to the sediments to progressively reach the transport capacity, and (iii) a two-layer model, able to account for the inertia of the sediment layer. Finally, three examples are presented: a scour hole downstream of an apron, a jump over a mobile bed, and a dam-break wave. Inertia effects appear significant in the modeling, especially the latter case.

It has been a traditional practice of fluvial engineers to apply the uniform water-flow hypothesis to real rivers by averaging the geometric and hydraulic quantities over appropriate portions of the river reach. No quantitative criterion, however, was applied to assess the validity and limitations of this procedure. The present paper collects a number of theoretical considerations and relevant observations (developed in the framework of two recent doctoral theses) that are quite useful for selecting the approximated model most suitable for studying morphodynamic problems at watershed scale. Particularly efficient for this analysis has been consideration of the river in quasi-equilibrium conditions.

During the past decade, significant research has been carried out on the strengthening of reinforced concrete (RC) slabs, beams, and columns using externally bonded carbon fibre reinforced polymer (CFRP) sheets. Steel reinforced polymer (SRP) sheets have recently been proposed as an alternative to CFRP to strengthen reinforced concrete beams. This paper reports experimental and numerical results of RC beams and beam-columns transversely wrapped with SRP and tested under blast load. A total of 10 scaled RC members were tested at a variety of blast wave intensities. Detailed observations are reported and validated against numerical models created in AUTODYN for the unstrengthened RC members. The SRP wraps were resilient in the near-field blast range and enhanced the ductility of the concrete likely through enhanced confinement. Member capacity could be increased by the wraps in failure modes dominated by concrete crushing. AUTODYN appears able to reasonably predict the behaviour of the RC members when loaded by blast.

There are many computational techniques to model the consequences to built infrastructure when subject to explosive blast loads; however, the majority of these do not account for the uncertainties associated with system response or blast loading. This paper describes a new computational model, called “Blast-RF” (Blast Risks for Facades), that incorporates existing (deterministic) blast-response models within an environment that considers threat and (or) vulnerability uncertainties and variability using probability and structural reliability theory. The structural reliability analysis uses stress limit states and the UK Glazing Hazard Guide's rating criteria to calculate probabilities of glazing damage and occupant safety hazards conditional on a given blast scenario. This allows the prediction of likelihood and extent of damage and (or) casualties, useful information for risk mitigation considerations, emergency service's contingency and response planning, collateral damage estimation, weaponeering, and post-blast forensic analysis.

In this paper, we discuss issues in verification, validation, and uncertainty prediction in computational fluid dynamics (CFD). Mesh adaptation is used to perform the systematic grid refinement studies required for code and simulation verification. We demonstrate the method of manufactured solutions (MMS) for code verification. Examples of successful and failed validation show that reliable prediction can only occur with an appropriate mathematical model of physics along with accurate numerical solution of the differential equations. The paper emphasizes good CFD practices to achieve systematic verification and put validation studies on solid grounds. Finally, the sensitivity equation method (SEM) is used to cascade input data uncertainty through the CFD code for estimating the uncertainty of the flow response.

In addition to a carbon source, bacteria require for growth a variety of nutrients such as phosphorus, potassium, and several other micronutrients including copper. The study described in this paper was conducted with the aim of determining the influence of phosphorus, potassium, and copper on methane elimination in a biofilter. The study revealed that the particular phosphorus concentration leading to the greatest methane elimination capacity, which was 44.7 g m–3 h–1at a methane inlet load of 75 g m–3 h–1, was 3.1 g/L. The influence of the phosphorus concentration on the methane elimination capacities was also investigated for methane inlet loads of between 8 and 95 g m–3 h–1. The optimum range of the nitrogen–phosphorus mass ratios, determined during this study ranged from 0.5 to 2.5. It was established that, in comparison with phosphorus, potassium does not seem to be a determining element for the biological removal efficiency and does not significantly affect the microorganisms’ behaviour. However, a concentration of 0.076 g/L of potassium is recommended in the irrigation nutrient solution for an inlet load of 75 g m–3 h–1. The influence of the copper concentration was also studied by varying its concentration between the values of 0 and 0.006 g/L. The results have also shown that copper has a minor impact on the biofiltration of methane. This paper is the first report describing the influence of several nutrients in a biofilter. The knowledge provided by this study is necessary for the achievement of a biofilter indebted to methane control.

Field and laboratory measurements of the transport of the suspended sediment from the Athabasca River near Hinton, Alberta, Canada are described. The objective of these measurements was to examine the influence of pulp mill effluent entering the river from a nearby pulp mill on suspended sediment. The results of the field measurement showed that the effluent had significant impact on the transport of the sediment. Specifically, the effluent increased the deposition rates of the sediment and caused a substantial reduction of sediment concentrations in reaches downstream of the effluent outfall. The reduction in sediment concentrations and the concomitant sediment loads can only be attributed to the pulp mill effluent as there were no abrupt changes in the hydraulic characteristics of the river in the reach of interest. These observations were confirmed by laboratory experiments that were carried out using a rotating circular flume located at the National Water Research Institute in Burlington, Ontario, Canada. The findings of this study have implications for modelling suspended sediment transport in rivers receiving bleached pulp mill effluents.

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.

Mathematical modelling of river processes is, nowadays, a key element in river engineering and planning. River modelling tools should rest on conceptual models drawn from mechanics of sediment transport, river mechanics, and river hydrodynamics. The objectives of the present work are (i) to describe conceptual models of sediment transport, deduced from grain-scale mechanics of sediment transport and turbulent flow hydrodynamics, and (ii) to present solutions to specific river morphology problems. The conceptual models described are applicable to the morphologic evolution of rivers subjected to the transport of poorly sorted sediment mixtures at low shear stresses and to geomorphic flows featuring intense sediment transport at high shear stresses. In common, these applications share the fact that sediment transport and flow resistance depend, essentially, on grain-scale phenomena. The idealized flow structures are presented and discussed. Numerical solutions for equilibrium and nonequilibrium sediment transport are presented and compared with laboratory and field data.

The enduring legacy of the Yalin equation of bedload transport is evaluated. The derivation of the equation includes three innovative aspects: (i) a rigorous use of dimensional analysis to simplify the formulation; (ii) a consideration of the randomness of grain placement rather than turbulence, resulting in a definable threshold of motion; and (iii) the introduction of a physically based, dynamic model of grain saltation into a bedload transport theory. The original relation remains useful today. In addition, the treatment of saltation has inspired an innovative line of research that continues to evolve today.

Starting from the model proposed by the authors to analyze the time-evolution of bedforms growing on the surface of an initially flat sand bed, the present study explores associated features of the bedform growth processes, including (i) mechanisms of growth, (ii) evolution of the bedform-induced drag, (iii) transition to antidunes, and (iv) non-equilibrium bedload sediment transport.

The size of the largest horizontal coherent structures (HCSs) of turbulence in open-channel flows is investigated experimentally on the basis of three series of flow velocity measurements. These are further used to explore the dynamics and morphological consequences of HCSs. The flow velocity measurements were carried out in a 21 m long and 1 m wide channel, with a bed formed by sand with average grain size of 2 mm. The bed surface was flat. The turbulent and subcritical flow under investigation was uniform, with a flow depth of 4 cm. The bed slope of 0.0015 was such that, for the present flow depth, the bed shear stress acting on the bed was substantially below the threshold for initiation of motion, thus ensuring that the bed remained flat throughout the measurements. To the knowledge of the writers, this work is a first attempt to systematically investigate HCSs in open-channel flows. It should be viewed as an extension to the case of horizontal structures of work previously carried out by a number of authors on large-scale organized turbulence motion in open-channel flows, so far focusing exclusively on vertical coherent structures (VCSs). The horizontal burst length was found to be between five and seven times the flow width. A slight internal meandering of the flow caused by the superimposition of burst sequences on the mean flow was detectable. Both of these findings lend support to the longstanding belief expressed by many prominent researchers that the formation of large-scale river forms is directly related to the large-scale turbulence. In particular, the present measurements for the first time provide some direct evidence in support of hypotheses previously raised by Yalin and da Silva regarding the formation of alternate bars and meanders through the action of HCSs on the mean flow and the mobile bed and banks.

Finished compost should be both stable (resistant to decomposition) and mature (ready for a particular end-use) so that it can safely be packaged and transported, and not cause adverse effects during its end use. A variety of methods for evaluating stability and maturity are available; this paper contains a review of the effectiveness of a number of the most commonly used tests, to determine the most reliable approach(es). In the literature reviewed, it was generally agreed that a single, stand-alone test for both compost stability and maturity does not yet exist; therefore, it is best to use a combination of tests. However, there is disagreement in the literature as to what the best combination for evaluation should be, and guidelines and regulations around the world employ a variety of approaches.

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 µm (PM10) with that for particulate matter with diameters less than 2.5 µm (PM2.5) at construction sites. A series of field-analogous experiments were carried out to continuously measure PM10 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 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 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.

Northern communities often have limited resources to resolve petroleum hydrocarbon (PHC) contamination. This project investigated an innovative approach for the management of diesel-contaminated soil in a remote community in Labrador. The soil was first treated in a passively aerated biopile to reduce the concentrations of mobile PHCs. The treated soil was then disposed of in the local landfill. Maximum total petroleum hydrocarbon (TPH) concentrations in soil, concentrations of PHCs with less than 16 carbons in soil, and TPH in leachate decreased during the 1 year field treatment. Microcosms incubated at 7 and 22 °C in the laboratory showed the potential for biodegradation of the PHCs. However, volatilization was likely the predominant PHC removal mechanism in the field. Disposal of treated soil to landfills has the advantage of transforming waste (i.e., soil) into a valued product (i.e., cover for the refuse). The development of risk-based guidelines for the disposal of PHC-contaminated soil into landfills in Canada appears to be needed and is discussed in this paper. Guidelines should be protective of the environment while prevent over-treatment of the soil, which may result in unnecessary spending and environmental impacts. The cost of the system tested was compared to that of treating soil in an off-site facility.

Masonry component products are increasingly made industrially with reduced variation in mechanical properties. The joint is the only part of the masonry that is affected by manual action and so the load bearing capacity is not only determined by the quality of the bricks and mortar used but moreover by the way the masonry has been built and cured. As a result, it may be expected that the largest material variations are at the brick–mortar interfaces. This has been observed as irregular interface bonding with a bonded central area surrounded by fissures. As a consequence of the final shape of the joint, forces concentrate in the central part of the joint and strain variations occur near fissure tips which result in spalling of bricks in experiments. This paper demonstrates the need for detailed deformational measurements in the brick–mortar interface region. To overcome the limitations with traditional measuring instruments, a refined methodology based on the laser speckle technique is introduced in a companion paper [Canadian Journal of Civil Engineering, 34(11), 1467 (2007)] by the authors of this paper.

The brick–mortar interaction is important in the mechanical behaviour of masonry. It affects the load transfer considerably, as shown by detailed deformation measurements taken using electronic speckle pattern interferometry (ESPI), a laser speckle interference technique. A companion paper [Canadian Journal of Civil Engineering, 34(11), 1475 (2007)] by the authors of this paper argues that the joint is the only part of contemporary masonry significantly affected by manual action, which is why large material variations appear at the brick–mortar interface. To evaluate this phenomenon, ESPI measurements were performed and compared with accompanying linear variable differential transformer (LVDT) results. The behaviour of specimens loaded with various eccentricities was relatively soft in the brick–mortar interface area when compared with the behaviour shown in the surrounding stiff brick and mortar. The brick–mortar interface was characterized by a central part surrounded by fissures. Most of the load was transmitted in the central part. Because of this, the axial strain curve over the width of the specimens was U-shaped for concentrically loaded specimens (i.e., those with zero eccentricity). Over the height of the two-brick one-joint specimen, a smooth, B-shaped lateral strain curve was observed, in which the largest strains were found in the bricks.

In this paper we present the study of catalytic oxidation of volatile organic compound (VOC) traces in air over Pt/γ-Al2O3 catalysts. The study was carried out using a laboratory fixed-bed catalytic reactor (FBCR) with catalytic oxidation of propene and toluene as model reactions. For better understanding of catalytic activity in a FBCR, the influence of operating parameters such as of platinum (Pt) loading, total gas flow rate, VOC concentration, and oxygen content were studied. The results showed that catalytic activity increases with increase in VOC concentration and a decrease in total gas flow rate. This displayed behaviour is instrumental to working at a low temperature region for complete oxidation of volatile organic compounds.

This paper gives an overview of the most important bioreactor configurations used in waste gas treatment, i.e., conventional and trickling biofilters, the bioscrubber, suspended-growth bioreactors, as well as two-liquid phase systems (stirred tank bioreactor and biotrickling filter). The historical evolution, main characteristics, and recent developments are described in each case.

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.

Biological air treatment is largely used for the decontamination of large air streams with low pollutant concentrations. As a result of microbial metabolism, the pollutants are degraded into carbon dioxide and water or converted into cell biomass. Three main research domains have emerged within the field of biofiltration: filter bed development, process optimization, and microbiological studies (community, nutrients, …). The objective of this paper is to focus on the microbial activities in air biofiltration processes. The nutrient contribution and the packing material effects are described. Special attention is paid to the description of techniques for the characterization and identification of the microbial population.

As a young, new, and rapidly growing science, the applications of ultrasound in environmental technology hold a promising future. Compared with conventional methods, ultrasonication can bring several benefits such as environmentally friendly (no toxic chemicals are used or produced), low cost, and compact (allowing on-site treatment). Beside an overview on ultrasonic background, this paper summarizes main findings and innovations of recent studies that used ultrasound in environmental analysis, water and sludge treatment, soil and sediment remediation, and air purification.

Because of changes in functional or security requirements, many new or existing buildings are now required to resist blast loads. New buildings can be designed and constructed to resist defined blast loads. Existing buildings, on the other hand, would have to rely on a risk assessment to determine both its vulnerability to blast effects and the necessary measures to mitigate the unacceptable blast effects. A rapid screening methodology has been developed for conducting a preliminary assessment of buildings against external blast effects. The methodology accounts for the threat, the vulnerability of the building, the consequence of an event and the risk, which is the product of the threat and the consequence. The rapid screening methodology has been applied to several buildings and the results are reasonable. This paper presents the rapid screening methodology and its application to two federal buildings in Canada.

This study critically discusses the fundamental concepts used for evaluating the flexural and axial resistance of structures under blast. Simplified methods based on single degree of freedom are emphasized. The paper begins with how to estimate the blast parameters for a given charge size and standoff distance. These parameters include side-on and reflected pressures, positive phase duration, and side-on and reflected impulses. Subsequently, blast damage criteria are defined in accordance with prevailing guidelines and some of their short comings are discussed. To assess the impact of blast on the flexural safety and performance of structures, some simple methods are presented. The methods are either empirical or are based on the principles of energy and momentum conservation. The analytical results are in closed-form or in the form of pressure–impulse (P–I) diagrams. The effect of strain rate on both blast-induced flexural deflection and strength of structures, with particular emphasis on reinforced concrete structures, is discussed.

Designers charged to develop blast-resistant structural designs must be able to address the technical aspects of the explosion process and provide structural components with sufficient strength and ductility to resist the applied pressures. The blast environment is different from those of other loads with which designers deal, and uncertainties about the actual response of structures often are higher. For these reasons, designers often have less confidence in their abilities to explain to their clients their expectations about the actual response of the building to a blast event. This paper identifies some elements of the conventional design process that do not translate directly to blast-resistant design, reasons why uncertainties in performance expectations differ from those encountered with other load sources, and the need to understand and acknowledge residual risks for the facade, the structure, and the safety of the occupants of blast resistant buildings.

Source water protection involves safeguarding water supplies from contamination and depletion. Despite best efforts, spills cannot always be prevented from entering a source water body. However, many spills can be prevented from entering a drinking water treatment plant if an early warning source water monitoring station is used. These stations provide downstream water utilities with advanced notification of spills so the utilities have time to implement their responses. This paper addresses the design of an early warning monitoring station for a riverine source of drinking water. Riverine water supplies face many threats related to accidental spills, which are inherently uncertain in nature. Therefore, designing a monitoring station for the detection of these events requires a probabilistic modelling approach. The design objectives include maximizing the probabilities of detection and of having a threshold amount of warning time. The methodology is applied to a water supply intake on the Grand River in southern Ontario.

This paper reports on the design of a new reactor configuration — an upflow fixed-bed combined anaerobic–aerobic reactor — can operate as a single treatment unit for the removal of nitrogen (≈150 mg N/L) and organic matter (≈1300 mg COD/L) from Lysine plant wastewater. L-Lysine, an essential amino acid for animal nutrition, is produced by fermentation from natural raw materials of agricultural origin, thus generating wastewater with high contents of organic matter and nitrogen. The best operational condition of the reactor was obtained with a hydraulic retention time of 35 h (21 h in the anaerobic zone and 14 h in the aerobic zone) and a recycling ratio (R) of 3.5. In this condition, the COD, total Kjeldahl nitrogen (TKN), and total nitrogen (TN) removal efficiencies were 97%, 96%, and 77%, respectively, with average effluent concentrations of 10 ± 36 mg COD/L, 2 ± 1 mg NH4+-N/L, 8 ± 3 mg Org-N/L, 1 ± 1 mg NH2–-N/L, and 26 ± 23 mg NH3–-N/L.

Membrane processes have become a competitive option to conventional treatment technologies because of the high quality of the product water. In particular, nanofiltration and reverse osmosis have been found to remove materials like natural organic matter, disinfection by-products, and endocrine-disrupting compounds. However, an issue identified as one of the major drawbacks for the adoption of pressure-driven membrane processes is the need for additional treatment of the concentrate stream. Few studies dealing with membrane concentrate treatment have been published. The majority of the published studies address the disposal of concentrate into receiving waters bodies and sewer systems. In this review paper, the characteristics of membrane concentrate in terms of water quality and their impact on receiving water bodies are discussed. In addition, several approaches to the removal of pollutants and disposal options for membrane concentrates are examined.

If natural windbreaks create air turbulence and can help disperse odours from livestock operations, their dispersion effect has not been extensively researched. This paper introduces a model simulating odour dispersion downwind from natural windbreaks. The standard k-ε model of the FLUENT software was used to incorporate the effect of climatic conditions and windbreak structure. The model was calibrated for wind velocity recovery, odour concentration (OC) from field observations and inertial resistance. Once calibrated, the model accurately reproduced the odour plume developing downwind from the windbreak. The correlation between OC for 11 field trials and that simulated were statistically significant (P < 0.01), indicating that the model was accurate. The model demonstrated that a windbreak did alter the magnitude and direction of the wind velocity, thus creating a pressure jump across its width. This pressure jump produces a strong downwind turbulence forming a mixing layer capable of enhancing odour dispersion.

Intentional contamination of drinking water with anthrax spores is a concern to water utilities. The spores may become embedded in the distribution pipe corrosion and biofilm, where they will be protected from residual disinfectants. This paper compares the disinfection effectiveness of chlorine and chlorine dioxide on Bacillus globigii , a surrogate for B. anthracis . Batch experiments were performed using both disinfectants. Data was analyzed using the delayed Chick-Watson model to determine the corresponding CTlag (CT = concentration × time) values and Watson plots, which indicate the dominant factors affecting disinfection kinetics. Chlorine dioxide had CTlag values almost one tenth of those observed for chlorine. However, Watson plots showed that exposure time and disinfectant concentrations have equal weights on the inactivation rate of both disinfectants.

A commercially available 3-D computational fluid dynamics (CFD) model (STAR-CD) was used to investigate capacity upgrading options for a combined sewer overflow (CSO) facility of inadequate capacity. The numerical model was verified against the data collected in two physical models. The need for verifying the CFD model was given by the complexity of the CSO facility, which comprises several interconnected tanks. The verified numerical model was then applied to analyze hydraulic conditions in the whole facility for major structural modifications with the aim of reducing or eliminating untreated overflows from the facility. Many scenarios were proposed and tested in the study and the two most promising structural modifications, scenarios 1 and 2, are presented in the paper. Both appeared to meet the design condition of increasing the facility capacity to 60 m3/s, but better performing scenario 1 would be significantly more costly to implement than scenario 2. Even though the study focused on a particular CSO facility, hydraulic conditions in the studied facility represent general flow conditions in typical CSO or stormwater settling facilities and, therefore, the numerical modeling methods used are applicable to solving a wide range of hydraulic problems encountered at similar facilities.