摘要:

Horseradish peroxidase enzyme (HRP), once activated by hydrogen peroxide, initiates the oxidation of a wide variety of aromatic compounds. Reaction products undergo a non-enzymatic polymerization to form water insoluble aggregates which are readily separated from solution. HRP was selected for application in wastewater treatment systems due to its stability and retention of its catalytic ability over wide ranges of pH and temperature. HRP activity was optimal between pH 5.7 and 8.5 with peak activity occurring at neutral pH. Activity increased with temperature up to 50 °C and declined at higher temperatures due to thermal inactivation. HRP was inactivated rapidly by hydrogen peroxide in the absence of an aromatic substrate. The efficiency of removal that was achieved was dependent on the nature of the aromatic undergoing treatment and the amount of enzyme provided due to the finite lifetime of the catalyst. Optimization of pH significantly improved catalytic efficiency with a corresponding savings in treatment costs. Optimal catalytic lifetime of HRP was achieved in the pH range of 7 to 9 for the eight phenolic compounds treated. The minimum residual level to which aromatic substrates were removed from solution was independent of the starting concentration of the aromatic substrate. Enhanced removal of hard-to-remove compounds was noted when mixtures of aromatic substrates were treated.Key words: horseradish peroxidase enzyme, polymerization, wastewater, phenols, aromatics amines.

ISSN:0315-1468    

DOI:10.1139/l93-097

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

In 1916, the Ottawa Improvement Commission, now the National Capital Commission, installed a concrete lamp-post to provide electric lighting along the Federal Driveway as part of its mandate to landscape and maintain parks and parkways in the capital. The design is highly significant both for its innovative use of materials and for its visual impact on the landscape. The lamp-post today is a heritage landmark, representative of urban reform introduced in the early 20th century under the influence of the City Beautiful movement.Key words: City Beautiful; urban design; street lighting; park furniture; Ottawa Improvement Commission; Lincoln Park, Chicago; Prairie School architecture.

ISSN:0315-1468    

DOI:10.1139/l93-098

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Eight large-scale reinforced concrete slab specimens were tested under combined thermal and mechanical load conditions. The specimens varied in the amount and orientation of the in-plane reinforcement provided. A three-phase loading regime was used to investigate thermal gradient effects at service and ultimate load conditions. The slabs experienced significant levels of stressing and cracking as a result of restrained thermal deformations. However, reductions in stiffness due to cracking and thermal creep caused rapid decays in the restraint forces developed. At ultimate load conditions, thermal load effects were minimal. Nonlinear finite element analysis procedures were used to investigate the theoretical response of the test slabs. Fairly accurate simulations of the specimens' behaviour were obtained. Important to achieving accurate results were the consideration of tension stiffening effects and out-of-plane shear behaviour.Key words: analysis, cracking, finite elements, plates, reinforced concrete, slabs, temperature, tests, thermal gradients.

ISSN:0315-1468    

DOI:10.1139/l93-099

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

A layered finite element model with material nonlinearity is developed to trace the nonlinear response of horizontally curved reinforced concrete box-girder bridges. Concrete is treated as an orthotropic nonlinear material and reinforcement is modeled as an elastoplastic strain-hardening material. Due to the fact that the flanges and webs of the structure are much different both in configuration and in the state of stresses, two types of facet shell elements, namely, the triangular generalized conforming element and the rectangular nonconforming element, are adopted to model them separately. A numerical example of a multi-cell box-girder bridge is given and the results are compared favourably with the experimental results previously obtained.Key words: finite element method, curved box-girder bridges, reinforced concrete, nonlinear analysis.

ISSN:0315-1468    

DOI:10.1139/l93-100

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

In hydrology, the Box–Cox power normal transformation has been found to perform well in a number of at-site and regional flood frequency studies. In this paper, an alternative to the maximum likelihood method of finding the Box–Cox transformation parameter, λ, is suggested. The proposed method is based on finding the λ that maximizes the correlation coefficient in the probability plot correlation coefficient test for normality. The proposed method of finding λ was tested on maximum daily discharge data from all over Canada and was found to give almost identical results to that obtained by the method of maximum likelihood. The main advantage of the proposed method is that finding the appropriate transformation and objectively testing whether the transformed data are normally distributed can be done in one step. In other methods, at least two steps are required. In addition, the proposed method makes use of techniques that are familiar to the hydrologist, namely, the probability plot and correlation analysis.Key words: flood frequency analysis, Box–Cox transformation, probability plotting, maximum likelihood method, Blom's plotting position, probability plot correlation coefficient test, correlation analysis, normal distribution.

ISSN:0315-1468    

DOI:10.1139/l93-101

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Process modelling can prove a useful tool for the control of wastewater treatment plants. The objective of this research was to verify that a primary settling model developped for a conventional process is applicable to a process using lamellar settling. The lumped-parameter model examines the hydraulics of a system composed of stirred tank reactors in series and simulates suspended solid concentration of the effluent under various flow regimes. The model has been validated using data collected from a pilot lamella settler of a capacity of 15 m3and operated over a wide range of flows (Hazen velocity between 0,43 and 2,59 m∙h−1). The prediction of the model was in agreement with the observed values both in terms of concentration and hydraulic behavior of effluent suspended solids (average relative error of 17%). How ever, less satisfactory was the model performance tested with the concentration data on settleable solids. Research is under way to study the different mechanisms of sedimentation going on in the settler.Key words: modelling, lamellar settling, settleable suspended solid

ISSN:0315-1468    

DOI:10.1139/l93-102

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

A generalized formulation of a procedure for optimum design of linear elastic plane frames under alternate loading condition is presented. The condition of alternate loading is employed to ensure that the optimum design, under individual application of envisaged load events, does not violate the limit state requirements on strength. The behavioral constraints both on strength and on displacement, including those of the axial load – moment interaction prescribed in code specifications, and the side constraints on member sizes are incorporated in the formulation. The method permits grouping of members to effect repetition and uniformity of member sizes, to a desired extent, throughout the structure. A predictor–corrector scheme is employed to arrive at the optimum design. The predicted design vector is expressed in terms of true member forces by an implicit scheme. In the correction phase, dynamic scaling and a unique process of step-size reduction are employed on the predicted design vector in the fully stressed design iteration to avoid bypassing an optimum during the search procedure. An algorithm for implementation of the proposed optimal design procedure is presented. The limit state design procedure of the Canadian Standard S16.1-M89, for members subjected to combined axial and bending action, is embedded in the algorithm. The algorithm is illustrated with an example problem and verified with results available in the literature.Key words: frames, optimum design, alternate loading, fully stressed, optimization, limit state.

ISSN:0315-1468    

DOI:10.1139/l93-103

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Several abandoned wood-preserving sites have been identified in Alberta, Canada, which pose a potential threat to human health and the environment. The physiochemical, environmental, and toxicological properties of wood preservatives are discussed together with the predominant human exposure pathways for these chemicals in the environment. A Level II soil fugacity model is used to illustrate the comparative environmental fate of individual organic wood treatment chemicals following release to the soil environment. An evaluation of risk management options at five priority sites is used to illustrate problems associated with the treatment and disposal of mixed organic and inorganic contaminated soils, soil property limitations, and the predominance of organic contaminants within the residual oil phase. The latter reality dominates options for exposure reduction and risk management.Key words: contaminated soils, wood-preserving sites, remediation options, screening, fugacity model.

ISSN:0315-1468    

DOI:10.1139/l93-104

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Strain gauges, along with an accelerometer and a linear variable displacement transducer, were used in the modal testing to detect a crack in a tripod tower platform structure model. The experimental results showed that the frequency response function of the strain gauge located near the crack had the most sensitivity to cracking. It was observed that the amplitude of the strain frequency response function at resonant points had large changes (around 60% when the crack became a through-thickness crack) when the crack grew in size. By monitoring the change of modal parameters, especially the amplitude of the strain frequency response function near the critical area, it would be very easy to detect the damage that occurs in offshore structures. A numerical computation of the frequency response functions using finite element method was also performed and compared with the experimental results. A good consistency between these two sets of results has been found. All the calculations required for the experimental modal parameters and the finite element analysis were carried out using the computer programSDRC-IDEAS.Key words: modal testing, cracking, strain–displacement–acceleration frequency response functions, frequency–damping–amplitude changes.

ISSN:0315-1468    

DOI:10.1139/l93-105

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Studies were conducted to demonstrate the effectiveness of copper sulphate for disinfection of sewage sludge under anaerobic conditions. The effects of suspended solids and copper dosages on the survival of total coliforms in normal (neutral pH) and acidified sludges (pH 2.1–3.8) were studied. Results indicated that disinfection of sewage sludge by copper sulphate was feasible. Under anaerobic conditions, significant reductions (about 99%) of total coliform bacteria in normal sludge were achieved at a dosage of 40 mg Cu/g dry sludge mass, sludge suspended solids of < 3.0%, and a contact time of 24 h. The toxic effect of copper dosage was enhanced and the copper dosage and contact time reduced at lower pH (2.1–3.8). Sludge so treated would be suitable for land application insofar as its bacteriological quality is concerned, provided the high copper concentration could be reduced to acceptable levels. Whether this can be achieved in subsequent treatment of disinfected sludge by bacterial leaching will be determined in a future study.Key words: sludge disinfection, coliforms, copper sulphate, sludge disposal, bacterial leaching.

ISSN:0315-1468    

DOI:10.1139/l93-106

出版商:NRC Research Press    

年代:1993

数据来源: NRC