... Imteaz, Monzur A 1 ; Hassan, Kazi I 2. Abstract: Due to the construction and associated river... more ... Imteaz, Monzur A 1 ; Hassan, Kazi I 2. Abstract: Due to the construction and associated riverbank protection works of Jamuna Multipurpose Bridge on Jamuna River at Bangladesh, water flow through the Old Dhaleswari River was reduced significantly. ...
Dhaka, the capital city of Bangladesh is facing a serious threat arising from the shortage of saf... more Dhaka, the capital city of Bangladesh is facing a serious threat arising from the shortage of safe, potable water, which has been traditionally obtained from local groundwater sources. As the ground water resource is becoming scarce and demand is increasing, DWASA (Dhaka Water And Sewerage Authority) is looking for a suitable surface water source to augment the water supply. But the quality of water in the peripheral rivers of Greater Dhaka has deteriorated significantly during the last few years. Specially in dry period, the situation is really alarming due to the uncontrolled disposal of untreated domestic and industrial sewage to the rivers. This study shows the latest status of river water quality during the d q period (December' 97 to February' 98) for several parameters as well as the major sources of pollution and pollution loadings from those sources in the Greater Dhaka. Results show at some locations, river water is polluted by heavy metals which exceed the allowable limit and are not removable by the traditional treatment processes. Detailed investigation has to be done for the selection of intake point for river water, if it is extracted during dry period.
A non-linear numerical model is developed for the computation of water level and discharge for th... more A non-linear numerical model is developed for the computation of water level and discharge for the propagation of a unidirectional two-layered tsunami wave. Four governing equations, two for each layer, are derived from Euler's equations of motion and continuity, assuming a long wave approximation, negligible friction and no interfacial mixing. A numerical model is developed using a staggered Leap-Frog scheme. The developed nonlinear model is compared with an existing validated linear model developed earlier by the author for different non-dimensional wave amplitudes. The significance of non-linear terms is discussed. It is found that for simulations of the interface wave amplitude, the effect of non-linear terms is not significant. However, for the simulation of the top surface, the effect of non-linear terms is significant for higher wave amplitudes, and insignificant for lower wave amplitudes. Developed non-linear numerical model is used for the case of a progressive internal wave in an inclined bay. It is found that the effect of an adverse bottom slipe towards the direction of wave propagation is to amplify the wave. This amplification depends on the steepness of slope as well as the ratio of densities of upper layer fluid to lower layer fluid (α). Amplification increases with slope. For higher values of α, amplification of the top and interface surface decreases, which is reasonable. It is also found that even for a 4 percent density difference between upper layer and lower layer, amplification of the top surface will be twenty times higher than amplification in the non-stratified case. The model can be applied confidently to simulate the basic features of different practical problems, similar to those investigated in this study.
A 2D analytical turbulent diffusion model for particle dispersion and deposition at different hei... more A 2D analytical turbulent diffusion model for particle dispersion and deposition at different heights along the pipe flow and circumferential deposition has been developed. This liquid-solid turbulent diffusion model presented in this paper has emanated from an existing gas-liquid turbulent diffusion model. This model can be used as a handy tool for quick estimation one and twodimensional deposition fluxes of particles in water distribution networks. A comprehensive 3D numerical investigation has been carried out using multiphase mixture model available in "Fluent 6.2" to verify the above analytical model. Different particles sizes and densities were used for 3D numerical investigations. The deposition was studied as a function of particle diameter, density, and fluid velocity. The deposition of particles, along the periphery of the pipe wall and at different depths, was investigated. Both the models findings matched with qualitative phenomena such as deposition of heavier particles at the bottom of the pipe wall were higher at lower velocities and lower at higher velocities. The lighter particles were found mostly suspended with homogeneous distribution. Smaller particles were also suspended with marginal higher concentration near the bottom of the pipe wall. This marginal higher concentration of the smaller particles was found to be slightly pronounced for lower velocity. These analogies of particles are well discussed with the ratio between freeflight velocity and the gravitational settling velocity. Extended analytical model results were compared with the 3D computational fluid dynamics simulation results. Discrepancies in the model results were discussed.
Swinburne University of Technology has constructed two 185 m 3 and 110 m 3 underground rainwater ... more Swinburne University of Technology has constructed two 185 m 3 and 110 m 3 underground rainwater tanks within Hawthorn campus in Melbourne. The main purpose of these tanks is to capture stormwater from the roof of some buildings and use the water for landscape irrigation. This paper presents an assessment of the effectiveness of these tanks to provide water for irrigation under different climatic scenarios (dry year, average year and wet year). Also, a payback period analysis of the tanks is presented. Traditionally, of the performance of such systems is analysed based on long-term average annual rainfall. However, analysis using long-term average rainfall does not depict the real situation as the total annual rainfall is not evenly distributed over the year but rather occurs as several random events of different magnitudes. To overcome this drawback, an analysis using real rainfall data for three different climatic conditions was performed. Historic rainfall data were collected from the Bureau of Meteorology for three different years (i.e., dry year -1st decile, average year -5th decile, and wet year -9th decile). A daily water balance model was developed and used to assess the effectiveness of the rainwater harvesting system considering daily rainfall data, total contributing roof area as catchment area, rainfall loss, available storage volume and irrigation water demand. The analysis showed that the tanks are highly effective, both in wet years and average years, also effective in dry years. A payback period analysis of the constructed tanks was preformed and the analysis revealed that the total cost can be recovered within couple of year time.
Http Dx Doi Org 10 1080 00207210802166856, Aug 28, 2008
This article presents an assessment of the first-order hydrothermal oxidation kinetics of a selec... more This article presents an assessment of the first-order hydrothermal oxidation kinetics of a selected digested sludge at subcritical (< 374 ° C) and supercritical (> 374 ° C) temperatures in the range of 250-460 ° C. Furthermore, the results were compared with reported oxidation kinetics of raw sludge treated under identical experimental conditions. In the assessment, oxidation was considered to proceed in two steps: (1) decomposition of the particulate, or non-filterable, chemical oxygen demand (PCOD); followed by (2) ultimate oxidation and removal of the total, particulate and soluble, COD. The accumulation and removal of soluble COD (SCOD) was determined from the difference between the rates of sludge decomposition and ultimate oxidation. Using results from batch and continuous-flow hydrothermal treatment experiments, the reacting organic ingredients were separated into groups according to the ease or difficulty at which they were decomposed or removed, with Arrhenius-type activation energy levels assigned to the different groups. The analysis confirmed that within the treatment range of 75% to more than 97% COD removal, the oxidation kinetics of the digested and raw sludges were nearly identical despite differences in the proportions of their original organic ingredients. The original organic ingredients were mostly removed above 75% COD removal, and the oxidation kinetics appeared to be dominated by the removal of acetic acid, an intermediate by-product which constituted 50% to more than 80% of the remaining COD. Furthermore, the oxidation kinetics of both sludge types were consistent with reported first-order oxidation kinetics of pure acetic acid solutions. The resulting kinetic models adequately represented hydrothermal oxidation of digested sludge, in terms of COD and PCOD removals, as well as accumulation and removal of the soluble SCOD.
ABSTRACT This research evaluates which is the most cost-efficient rainwater harvesting (RWH) syst... more ABSTRACT This research evaluates which is the most cost-efficient rainwater harvesting (RWH) system in a new commercial building located in the north of Portugal, in Braga. Based on the economic analysis, the cost-efficiency of the presented RWH strategies may be considered for the case studied. The results of this research indicate that RWH scenarios proposed are cost-efficient. Considering a 10 % discount rate, the water price charge in the municipally of Braga and the cost of the infrastructures would be enough to make RWH cost-efficient for this option. At this discount rate, the payback period ranges from 2 to 6 years and the internal rate of return would range from 23 to 76 %. If a discount rate of 5 % were considered, the payback periods would be reduced by approximately 1 year.
Construction and demolition (C&D) materials are defined as the materials obtained from demolition... more Construction and demolition (C&D) materials are defined as the materials obtained from demolition activities such as crushed concrete, crushed brick and reclaimed asphalt. The disposal of these materials in landfills is a major problem to the environment. The urgency and significance of recycling C&D materials has been raised because of scarcity of natural aggregates, difficulties in finding landfill and other environmental concerns. Hence, the present paper describes the physical and geotechnical characteristics of recycled crushed brick (CB) to reuse in different civil engineering applications. The laboratory experiments involved modified compaction test, particle size distribution, specific gravity, water absorption and Los Angeles abrasion. Furthermore, the interface shear strength properties of the CB material with geogrids and their performance as a pavement subbase material was ascertained by using a large direct shear testing (DST) apparatus. The higher tensile strength triaxial geogrid was found to attain higher interface shear strength properties than that of the lower tensile strength biaxial geogrid. The DST results however indicated that the interface shear strength properties of the geogrid-reinforced CB material were less than that of the respective material without reinforcement. The results were also found to meet the peak and residual shear strength and local road authority requirements for typical construction materials in civil engineering applications.
AbstractÐIn order to develop a method of predicting and assessing lake eutrophication, which is a... more AbstractÐIn order to develop a method of predicting and assessing lake eutrophication, which is a serious environmental problem, and to propose eective measures for improvement of water quality, this paper presents a composite model of the mixing of lake water by air bubble plume and lake phytoplankton model. The equations of heat and mass transfer in the lake were solved together with equations governing physical and biological processes under real atmospheric conditions coupled with an integrated model of bubble plume. The veri®cation of the model was conducted using data of Lake Calhoun (USA). Using the developed model, numerical experiments were carried out for an imaginary lake in the Hiroshima region of Japan with dierent gas¯ow rates of bubble plume, dierent numbers of bubble ports, dierent starting dates of bubbler and dierent bubbler depths. The optimization of the improvement of water quality in the lake can be obtained by using the appropriate gas¯ow rate and number of bubble ports, and applying it at an appropriate period of the year. #
This paper presents development of a one-dimensional stream water quality model for the continuou... more This paper presents development of a one-dimensional stream water quality model for the continuous simulations of suspended sediments, biochemical oxygen demand (BOD), total phosphorus (TP) and total nitrogen (TN) along a particular stream section. The model first integrates stream hydraulics and suspended sediments transport and deposition processes. Then computations of degradation of water quality parameters (BOD, TP and TN) are incorporated with the hydraulic-sediment transport model. The stream hydraulic model was developed using Muskingum-Cunge method of channel routing. The well known suspended sediment transport/deposition processes have been modified and integrated with the developed hydraulic model. The developed water quality model was applied and simulated for the Saltwater Creek, Gold Coast, Australia. Sensitivity analysis of the model showed that all the particles characteristics within incoming stream flows are important for the better prediction of suspended sediment loads.
... Imteaz, Monzur A 1 ; Hassan, Kazi I 2. Abstract: Due to the construction and associated river... more ... Imteaz, Monzur A 1 ; Hassan, Kazi I 2. Abstract: Due to the construction and associated riverbank protection works of Jamuna Multipurpose Bridge on Jamuna River at Bangladesh, water flow through the Old Dhaleswari River was reduced significantly. ...
Dhaka, the capital city of Bangladesh is facing a serious threat arising from the shortage of saf... more Dhaka, the capital city of Bangladesh is facing a serious threat arising from the shortage of safe, potable water, which has been traditionally obtained from local groundwater sources. As the ground water resource is becoming scarce and demand is increasing, DWASA (Dhaka Water And Sewerage Authority) is looking for a suitable surface water source to augment the water supply. But the quality of water in the peripheral rivers of Greater Dhaka has deteriorated significantly during the last few years. Specially in dry period, the situation is really alarming due to the uncontrolled disposal of untreated domestic and industrial sewage to the rivers. This study shows the latest status of river water quality during the d q period (December' 97 to February' 98) for several parameters as well as the major sources of pollution and pollution loadings from those sources in the Greater Dhaka. Results show at some locations, river water is polluted by heavy metals which exceed the allowable limit and are not removable by the traditional treatment processes. Detailed investigation has to be done for the selection of intake point for river water, if it is extracted during dry period.
A non-linear numerical model is developed for the computation of water level and discharge for th... more A non-linear numerical model is developed for the computation of water level and discharge for the propagation of a unidirectional two-layered tsunami wave. Four governing equations, two for each layer, are derived from Euler's equations of motion and continuity, assuming a long wave approximation, negligible friction and no interfacial mixing. A numerical model is developed using a staggered Leap-Frog scheme. The developed nonlinear model is compared with an existing validated linear model developed earlier by the author for different non-dimensional wave amplitudes. The significance of non-linear terms is discussed. It is found that for simulations of the interface wave amplitude, the effect of non-linear terms is not significant. However, for the simulation of the top surface, the effect of non-linear terms is significant for higher wave amplitudes, and insignificant for lower wave amplitudes. Developed non-linear numerical model is used for the case of a progressive internal wave in an inclined bay. It is found that the effect of an adverse bottom slipe towards the direction of wave propagation is to amplify the wave. This amplification depends on the steepness of slope as well as the ratio of densities of upper layer fluid to lower layer fluid (α). Amplification increases with slope. For higher values of α, amplification of the top and interface surface decreases, which is reasonable. It is also found that even for a 4 percent density difference between upper layer and lower layer, amplification of the top surface will be twenty times higher than amplification in the non-stratified case. The model can be applied confidently to simulate the basic features of different practical problems, similar to those investigated in this study.
A 2D analytical turbulent diffusion model for particle dispersion and deposition at different hei... more A 2D analytical turbulent diffusion model for particle dispersion and deposition at different heights along the pipe flow and circumferential deposition has been developed. This liquid-solid turbulent diffusion model presented in this paper has emanated from an existing gas-liquid turbulent diffusion model. This model can be used as a handy tool for quick estimation one and twodimensional deposition fluxes of particles in water distribution networks. A comprehensive 3D numerical investigation has been carried out using multiphase mixture model available in "Fluent 6.2" to verify the above analytical model. Different particles sizes and densities were used for 3D numerical investigations. The deposition was studied as a function of particle diameter, density, and fluid velocity. The deposition of particles, along the periphery of the pipe wall and at different depths, was investigated. Both the models findings matched with qualitative phenomena such as deposition of heavier particles at the bottom of the pipe wall were higher at lower velocities and lower at higher velocities. The lighter particles were found mostly suspended with homogeneous distribution. Smaller particles were also suspended with marginal higher concentration near the bottom of the pipe wall. This marginal higher concentration of the smaller particles was found to be slightly pronounced for lower velocity. These analogies of particles are well discussed with the ratio between freeflight velocity and the gravitational settling velocity. Extended analytical model results were compared with the 3D computational fluid dynamics simulation results. Discrepancies in the model results were discussed.
Swinburne University of Technology has constructed two 185 m 3 and 110 m 3 underground rainwater ... more Swinburne University of Technology has constructed two 185 m 3 and 110 m 3 underground rainwater tanks within Hawthorn campus in Melbourne. The main purpose of these tanks is to capture stormwater from the roof of some buildings and use the water for landscape irrigation. This paper presents an assessment of the effectiveness of these tanks to provide water for irrigation under different climatic scenarios (dry year, average year and wet year). Also, a payback period analysis of the tanks is presented. Traditionally, of the performance of such systems is analysed based on long-term average annual rainfall. However, analysis using long-term average rainfall does not depict the real situation as the total annual rainfall is not evenly distributed over the year but rather occurs as several random events of different magnitudes. To overcome this drawback, an analysis using real rainfall data for three different climatic conditions was performed. Historic rainfall data were collected from the Bureau of Meteorology for three different years (i.e., dry year -1st decile, average year -5th decile, and wet year -9th decile). A daily water balance model was developed and used to assess the effectiveness of the rainwater harvesting system considering daily rainfall data, total contributing roof area as catchment area, rainfall loss, available storage volume and irrigation water demand. The analysis showed that the tanks are highly effective, both in wet years and average years, also effective in dry years. A payback period analysis of the constructed tanks was preformed and the analysis revealed that the total cost can be recovered within couple of year time.
Http Dx Doi Org 10 1080 00207210802166856, Aug 28, 2008
This article presents an assessment of the first-order hydrothermal oxidation kinetics of a selec... more This article presents an assessment of the first-order hydrothermal oxidation kinetics of a selected digested sludge at subcritical (< 374 ° C) and supercritical (> 374 ° C) temperatures in the range of 250-460 ° C. Furthermore, the results were compared with reported oxidation kinetics of raw sludge treated under identical experimental conditions. In the assessment, oxidation was considered to proceed in two steps: (1) decomposition of the particulate, or non-filterable, chemical oxygen demand (PCOD); followed by (2) ultimate oxidation and removal of the total, particulate and soluble, COD. The accumulation and removal of soluble COD (SCOD) was determined from the difference between the rates of sludge decomposition and ultimate oxidation. Using results from batch and continuous-flow hydrothermal treatment experiments, the reacting organic ingredients were separated into groups according to the ease or difficulty at which they were decomposed or removed, with Arrhenius-type activation energy levels assigned to the different groups. The analysis confirmed that within the treatment range of 75% to more than 97% COD removal, the oxidation kinetics of the digested and raw sludges were nearly identical despite differences in the proportions of their original organic ingredients. The original organic ingredients were mostly removed above 75% COD removal, and the oxidation kinetics appeared to be dominated by the removal of acetic acid, an intermediate by-product which constituted 50% to more than 80% of the remaining COD. Furthermore, the oxidation kinetics of both sludge types were consistent with reported first-order oxidation kinetics of pure acetic acid solutions. The resulting kinetic models adequately represented hydrothermal oxidation of digested sludge, in terms of COD and PCOD removals, as well as accumulation and removal of the soluble SCOD.
ABSTRACT This research evaluates which is the most cost-efficient rainwater harvesting (RWH) syst... more ABSTRACT This research evaluates which is the most cost-efficient rainwater harvesting (RWH) system in a new commercial building located in the north of Portugal, in Braga. Based on the economic analysis, the cost-efficiency of the presented RWH strategies may be considered for the case studied. The results of this research indicate that RWH scenarios proposed are cost-efficient. Considering a 10 % discount rate, the water price charge in the municipally of Braga and the cost of the infrastructures would be enough to make RWH cost-efficient for this option. At this discount rate, the payback period ranges from 2 to 6 years and the internal rate of return would range from 23 to 76 %. If a discount rate of 5 % were considered, the payback periods would be reduced by approximately 1 year.
Construction and demolition (C&D) materials are defined as the materials obtained from demolition... more Construction and demolition (C&D) materials are defined as the materials obtained from demolition activities such as crushed concrete, crushed brick and reclaimed asphalt. The disposal of these materials in landfills is a major problem to the environment. The urgency and significance of recycling C&D materials has been raised because of scarcity of natural aggregates, difficulties in finding landfill and other environmental concerns. Hence, the present paper describes the physical and geotechnical characteristics of recycled crushed brick (CB) to reuse in different civil engineering applications. The laboratory experiments involved modified compaction test, particle size distribution, specific gravity, water absorption and Los Angeles abrasion. Furthermore, the interface shear strength properties of the CB material with geogrids and their performance as a pavement subbase material was ascertained by using a large direct shear testing (DST) apparatus. The higher tensile strength triaxial geogrid was found to attain higher interface shear strength properties than that of the lower tensile strength biaxial geogrid. The DST results however indicated that the interface shear strength properties of the geogrid-reinforced CB material were less than that of the respective material without reinforcement. The results were also found to meet the peak and residual shear strength and local road authority requirements for typical construction materials in civil engineering applications.
AbstractÐIn order to develop a method of predicting and assessing lake eutrophication, which is a... more AbstractÐIn order to develop a method of predicting and assessing lake eutrophication, which is a serious environmental problem, and to propose eective measures for improvement of water quality, this paper presents a composite model of the mixing of lake water by air bubble plume and lake phytoplankton model. The equations of heat and mass transfer in the lake were solved together with equations governing physical and biological processes under real atmospheric conditions coupled with an integrated model of bubble plume. The veri®cation of the model was conducted using data of Lake Calhoun (USA). Using the developed model, numerical experiments were carried out for an imaginary lake in the Hiroshima region of Japan with dierent gas¯ow rates of bubble plume, dierent numbers of bubble ports, dierent starting dates of bubbler and dierent bubbler depths. The optimization of the improvement of water quality in the lake can be obtained by using the appropriate gas¯ow rate and number of bubble ports, and applying it at an appropriate period of the year. #
This paper presents development of a one-dimensional stream water quality model for the continuou... more This paper presents development of a one-dimensional stream water quality model for the continuous simulations of suspended sediments, biochemical oxygen demand (BOD), total phosphorus (TP) and total nitrogen (TN) along a particular stream section. The model first integrates stream hydraulics and suspended sediments transport and deposition processes. Then computations of degradation of water quality parameters (BOD, TP and TN) are incorporated with the hydraulic-sediment transport model. The stream hydraulic model was developed using Muskingum-Cunge method of channel routing. The well known suspended sediment transport/deposition processes have been modified and integrated with the developed hydraulic model. The developed water quality model was applied and simulated for the Saltwater Creek, Gold Coast, Australia. Sensitivity analysis of the model showed that all the particles characteristics within incoming stream flows are important for the better prediction of suspended sediment loads.
In order to understand the hydrodynamics of a river basin, it is essential to evaluate its discha... more In order to understand the hydrodynamics of a river basin, it is essential to evaluate its discharge capacity. It is a challenge though, particularly for an ungauged basin, as the discharge frequently changes due to geometric and climate features. Hydraulic models, calibrated with reliable measured data, are efficient tools to assess river basin flow characteristics. In the study, HEC-RAS was used to model water levels in three cross-sections of the Juqueriquere river basin, located in the northern coastline of Sao Paulo State, Brazil. The Manning's roughness coefficients for these locations were adjusted to fit with the measured data and corresponded to the bed, left & right banks of Camburu, Claro and Areeiro gauging stations. These coefficients were compared with the earlier estimated n-values, which were based on a theoretical approach and field campaigns. The absolute deviation and Mean Absolute Deviation (MAD) values between the estimated and calibrated Manning's n-values were calculated for each cross-section. It was found that, for some cases, calibrated n-values did not match with the theoretical estimations. The reasons for these discrepancies are discussed in this paper.
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