Electrochemical Advanced Oxidation Processes (eAOPs) such as the current Advanced Oxidation Syste... more Electrochemical Advanced Oxidation Processes (eAOPs) such as the current Advanced Oxidation System (AOS) are a type of electrochemical wastewater treatment that creates oxidative species, such as iodide species, chloride species, and hydroxyl radicals, that can treat even recalcitrant contaminants. It is important to determine the concentrations and locations of oxidative species in eAOPs for optimization of the wastewater treatment process. In this study, a spectrophotometric methodology was used to determine concentrations of iodide and chloride oxidative species (starting at 10, 25, and 50 ppm) within an AOS under various input voltages (6, 12, and 24 V). Overall, it was found that iodate and chlorite were the dominant species created in their respective treatments. Additionally, the concentration of iodide oxidative species increases with increasing voltage, whereas the chloride species decrease with increasing voltage. The optimal conditions for the e cient creation of AOS oxidative species were 12 V and 10 ppm potassium iodide and 6 V and 10 ppm sodium chloride, respectively. In addition, the use of iodide is recommended for wastewater treatment using the AOS to effectively create oxidative species. Following optimization, the AOS performance was tested for a synthetic stormwater. Results indicated that the AOS performed well for reduction of Eschericha coli; however, reduction of other contaminants was inconsistent as would be expected given the AOS was optimized for disinfection, not decontamination. Further AOS optimization for decontamination would lead to improved decontamination performance.
Journal of Engineering Science and Technology, 2012
The amount of rainfall received over an area is an important factor in assessing availability of ... more The amount of rainfall received over an area is an important factor in assessing availability of water to meet various demands for agriculture, industry, irrigation, generation of hydroelectricity and other human activities. The distribution of rainfall in time and space is, therefore, an important factor for the economic development of a country. Due to rapid urbanization in various parts of the north-eastern region of Bangladesh, there is a growing need to study the rainfall pattern, and also frequency of the heavy rainfall events. This study was checked monthly average rainfall from daily records of last 50 years for this region. In order to check the major events, time history of monthly rainfall data were transformed into frequency domain using the Fast Fourier Transform (FFT). Estimated peak frequency (11.98 month) depicts that major rainfall events of a year are occurring earlier than the previous year. The variability of rainfall in time scale was also checked from filtered ...
An understanding of the nature of wastewater is essential in the design and operation of collecti... more An understanding of the nature of wastewater is essential in the design and operation of collection, treatment, and disposal facilities and in the engineering management of environmental quality. Municipal wastewater of Sylhet city, divisional city of the northeastern region of Bangladesh, originates from different types of sources and then falls into the Surma River through different channels. Malni Chara, the largest channel falling into the Surma River originating from a hilly tea garden was selected for the study. In this study, physical parameters (total solids, dissolved solids, suspended solids, pH) and chemical parameters (BOD, alkalinity, DO, chlorides, nitrates, oil and grease) of wastewater were measured. Maximum value of total solids was found in the Stadium area (600mg/l). pH was found to be almost the same at every point (around 6.5). Maximum nitrates and chlorides were found in Subid Bazar (0.2 mg/L) and the Stadium area (42 mg/L) respectively. The findings of the study conclude that the quality of the wastewater of Sylhet city is medium for suspended solids, BOD 5 and chlorides, and strong for alkalinity.
ii CO-AUTHORSHIP iv ACKNOWLEDGEMENTS vii DEDICATION viii TABLE OF CONTENTS ix LIST OF TABLES xvi ... more ii CO-AUTHORSHIP iv ACKNOWLEDGEMENTS vii DEDICATION viii TABLE OF CONTENTS ix LIST OF TABLES xvi LIST OF FIGURES xviii LIST OF SYMBOLS xxv CHAPTER
We present an electrochemical advanced oxidation process (eAOP) reactor employing expanded graphi... more We present an electrochemical advanced oxidation process (eAOP) reactor employing expanded graphite, potassium iodide (KI), and electrical current, which demonstrates an exceptionally high rate of inactivation of E. coli (6log reduction in viable cells) at low current density 0.6 mA/cm^2), with low contact time (5 minutes) and low concentration of KI (10 ppm). Operando X-ray fluorescence mapping is used to show the distribution of iodine species in the reactor, and operando X-ray absorption spectroscopy in the anodic chamber reveals iodine species with higher effective oxidation state than periodate. Operando electrochemical measurements confirm the conditions in the anodic chambers are favourable for the creation of highly oxidized iodine products. The killing efficiency of this new eAOP reactor far exceeds that expected from either traditional iodine-based electrochemical water treatment or advanced oxidation systems alone, a phenomenon that may be associated with the production o...
An understanding of the nature of wastewater is essential in the design and operation of collecti... more An understanding of the nature of wastewater is essential in the design and operation of collection, treatment, and disposal facilities and in the engineering management of environmental quality. Municipal wastewater of Sylhet city, divisional city of the northeastern region of Bangladesh, originates from different types of sources and then falls into the Surma River through different channels. Malni Chara, the largest channel falling into the Surma River originating from a hilly tea garden was selected for the study. In this study, physical parameters (total solids, dissolved solids, suspended solids, pH) and chemical parameters (BOD, alkalinity, DO, chlorides, nitrates, oil and grease) of wastewater were measured. Maximum value of total solids was found in the Stadium area (600mg/l). pH was found to be almost the same at every point (around 6.5). Maximum nitrates and chlorides were found in Subid Bazar (0.2 mg/L) and the Stadium area (42 mg/L) respectively. The findings of the study conclude that the quality of the wastewater of Sylhet city is medium for suspended solids, BOD 5 and chlorides, and strong for alkalinity.
Oil sands mines generate tailings during the extraction process, which are a mixture of water, cl... more Oil sands mines generate tailings during the extraction process, which are a mixture of water, clay, sand and residual bitumen. When the tailings are released to tailings ponds, the coarse solids settle quickly, whereas fine solids containing clay minerals, namely mature fine tailings (MFT), remain suspended for years, even decades. A study is carried out to assess the suitability of electrokinetic (EK) sedimentation to accelerate sedimentation of MFT. A series of laboratory-scale column experiments are carried out to examine the effects of electrophoresis during settling processes. The investigation focuses on the effects of EK sedimentation as related to the initial solid content of the tailings suspension, applied electric field intensity, water pH, and the use of an optimized coagulant FeCl 3. Based on the experimental data, an electric field intensity of 150 V/m along with an initial tailings solid content of no N5% are the optimum condition for EK sedimentation of MFT, in terms of reducing the overall sedimentation time and increasing the final solid content. The results show that the current density of EK sedimentation for MFT should not be N 20 A/m 2 to control the bubble effect and reduce power consumption.
An understanding of the nature of wastewater is essential in the design and operation of collecti... more An understanding of the nature of wastewater is essential in the design and operation of collection, treatment, and disposal facilities and in the engineering management of environmental quality. Municipal wastewater of Sylhet city, divisional city of the northeastern region of Bangladesh, originates from different types of sources and then falls into the Surma River through different channels. Malni Chara, the largest channel falling into the Surma River originating from a hilly tea garden was selected for the study. In this study, physical parameters (total solids, dissolved solids, suspended solids, pH) and chemical parameters (BOD, alkalinity, DO, chlorides, nitrates, oil and grease) of wastewater were measured. Maximum value of total solids was found in the Stadium area (600mg/l). pH was found to be almost the same at every point (around 6.5). Maximum nitrates and chlorides were found in Subid Bazar (0.2 mg/L) and the Stadium area (42 mg/L) respectively. The findings of the study conclude that the quality of the wastewater of Sylhet city is medium for suspended solids, BOD 5 and chlorides, and strong for alkalinity. Introduction Sylhet city has been taken as our study area, which is an important divisional city located in the northeastern part of Bangladesh (Latitude: 24.857deg; N, Longitude: 91.80° E). Sylhet Municipality was established in 1878.The area of the town is 10.49 sq. km. It has a population of 285,308; density of population is 27,198 per sq km (Banglapedia, 2006). The city is situated beside the Surma River. The wastewater effluent from Sylhet city discharged to the Surma River is polluting the river water, as treatment facilities are not yet established in Sylhet. As the quality of wastewater is not satisfactory, problems like pollution of the Surma River and the streams, deterioration of the environment, and health sanitation have become serious. Obviously it is necessary to evaluate the wastewater discharge and disposal system in order to determine the effects of wastewater discharges on receiving water or the public sewer or on any proposed treatment process and to explore possible treatment process requirements to eliminate such effects. Objectives of the Study This study essentially focuses on the greater importance of analysis and design of an effective and economic rational sewage treatment system for Sylhet city. The present sewerage problems of Sylhet city set the objective of this study to characterize the combined sewage of Sylhet city, assessing the pollution level of wastewater that is discharged into the Surma River and polluting the water. Study Area This study was conducted in Sylhet city. The sewerage network of Sylhet city consists of many small drains connected with some natural hilly channels called 'Chara', which fall into the Surma River. Besides these, there are some other big natural channels, which interconnect the 'Charas'. Those natural channels are known as 'Khal'. The main 'Charas' in Sylhet city are Malni Chara, Goali Chara, Jugni Chara, and Mira Chara. Among the Khals, Khal of Mira Bazar, Khal of Niorpool, Khal of Jallar Par, Monipuri-Rajbari Khal, Khal of Taltola, and Khal of Sheikhghat are important (Alam, Nath & Siddique, 2002). The study route Malni Chara is the largest chara, which originates from Malni Chara Tea Garden and then divides into two branches. The main branch of the chara goes through a housing estate, Darga Moholla, Sylhet Stadium area, and Taltola and falls into the Surma River near Kazir Bazar. This branch of Malni Chara was selected for the study. Another branch goes through Sagar Dighir Par and the Osmani Medical College Hospital area and falls into the Surma River. Methodology Laboratory data are essential to design wastewater treatment facilities in urban areas. To obtain such data for Sylhet city, six sampling points on the main branch of Malni Chara have been selected according to their importance. …
Air-stripping method was used to remove ammonia from the wastewater collected from natural gas fe... more Air-stripping method was used to remove ammonia from the wastewater collected from natural gas fertilizer factory. Different materials were used as packing materials for the air stripping system. The effect of pH over 10.5, air-water flow ratio, nature of packing materials, height of materials and initial influent concentration of ammonia on air stripping unit were investigated. An attempt has been made to find out the stripping constant. Stripping constant was found to be .001, 0014, .001 and .0009 for coal, plastic ring, stone chips and wood chips, respectively. Best result was found for plastic ring for its higher surface area. Wood chips did not give good result, because the chips amalgamate with each other and hence reduces the surface area.
International Journal of Environmental Science and Technology, 2013
A sample preparation method of total sulphur measurement of reactive mine tailings was optimized.... more A sample preparation method of total sulphur measurement of reactive mine tailings was optimized. The total sulphur was measured by inductively coupled plasma optical emission spectroscopy, and ultrasound technique was used for sample digestion. The optimization process was adopted by a combined approach of experimental design and response surface methodology. The digestion time, temperature and acid-oxidant combination (i.e. effect of H 2 O 2 with a fixed amount of acid mixture) were investigated. A two-level and three-factor (2 3) full factorial design of experiment was applied to identify the most significant factors, and a central composite design was used to optimize the digestion procedure. KZK-1, a sericite schist, was selected as the certified reference material. The optimum methodology at 95 % confidence level (P \ 0.05) was identified to be 10 min of digestion at 77°C, with a solution of 1 ml HNO 3 :1 ml HCl:1.35 ml H 2 O 2. This combination resulted in 100 % sulphur recovery. The investigated method was verified by X-ray diffraction analysis. The optimum digestion level was applied to a reactive mine tailings, which achieved satisfactory results with a percentage relative standard deviation \ 3 %.
The physical, chemical and biological characteristics of the wastewater of Natural Gas Fertilizer... more The physical, chemical and biological characteristics of the wastewater of Natural Gas Fertilizer Factory Ltd. Fenchuganj, Sylhet were determined through extensive laboratory tests in the months of March, July, October and December of the year 2005. Concentration of Suspended Solids was within the range of 445 to 950 mg/L. Bangladesh Industrial Effluent Standards for Suspended Solids is 100 mg/L. Suspended Solids were found above the limit in all the samples. Concentration of Dissolved Solids was found to vary from 576 to 1,456 mg/L. Bangladesh Industrial Effluent Standards, for Dissolved Solids is 2,100 mg/L. Dissolved Solids were found within the limit. Concentration of BOD(5) was found to vary from 4.5 to 8.4 mg/L. Bangladesh Industrial Effluent Standards for BOD(5) is 50 mg/L. For the year 2005, the BOD(5) was found below the limit in all the samples. Dissolved Oxygen of the wastewater was found to be between 2.0 to 3.0 mg/L, which do not satisfy the standard (4.5-8 mg/L). Oil and grease concentration were found in the range of 28 to 68 mg/L, whereas the standard is 10 mg/L for discharge into the inland surface water. In 2005, concentration of Cr(+ 6) was found to vary from 0.01 to 0.156 mg/L in the wastewater. Bangladesh Industrial Effluent Standards, for Cr(+6) is 0.1 mg/L. The concentration of chromium was found above the limit in three samples. Concentration of NO(3) was found to vary from 4.5 to 15.2 mg/L in the wastewater. Bangladesh Industrial Effluent Standards for nitrate is 10 mg/L. The nitrate was found above the limit in three samples. Maximum concentration of ammonia in lagoon 1 was found 1,710 mg/L in month of December. Bangladesh Industrial Effluent Standards for ammonia nitrogen is 100 mg/L. For the year 2005, the ammonia nitrogen was found above the limit in all samples.
The oxidation of sulphidic mine tailings and consequent acid generation poses challenges for the ... more The oxidation of sulphidic mine tailings and consequent acid generation poses challenges for the environment. Accurate and precise analysis of sulphur content is necessary for impact assessment and management of mine tailings. Here, the authors aim at developing a rapid and easy digestion procedure, which may analyse and measure the total amount of sulphur in mine tailings by using inductively coupled plasma. For evaluating effects of several variables, the researchers used a univariate (analysis of variance (ANOVA)) strategy and considered factors such as composition of the acid mixture, heating time, and refluxing device to optimize the performance. To do the experiment, the researchers have used two certified reference materials (KZK-1 and RTS-2) and samples of tailings from Musselwhite mine. ANOVA result shows that heating time is the most influencing factor on acid digestion of the reference materials whereas in case of a digestion of tailings sample, hydrochloric acid proved to be the most significant parameter. Satisfactory results between the measured and referenced values are found for all experiments. It is found that the aqua regia (1 ml HNO(3) + 3 ml HCl) digestion of 0.1 g of samples after only 40 min of heating at 95°C produced fast, safe, and accurate analytical results with a recovery of 97% for the selected reference materials.
Arsenic contaminated sludge can be found from the treatment of arsenic contaminated ground water.... more Arsenic contaminated sludge can be found from the treatment of arsenic contaminated ground water. Lake of management and reuse of this sludge can create further environmental problem as there is probability of mixing with soil and water. In this paper, an effort is taken for the use of such waste. Here, effectiveness of using this sludge in making ornamental brick has been analyzed and justified. The detailed study was made upon the suitability of sludge in making bricks. Results of different tests indicate that sludge proportion is the key factor for determining the quality of ornamental bricks/tiles. The compressive strength of ornamental bricks decreases with increase of sludge proportion. This study showed that arsenic contaminated sludge could be used safely up to 4 % for making ornamental bricks. Because after that limit the quality of bricks or tiles fall markedly.
A study of the water quality conditions of Sylhet city of Bangladesh and its restaurants was carr... more A study of the water quality conditions of Sylhet city of Bangladesh and its restaurants was carried out to assess risks to human health. The investigation was based on questionnaire survey of restaurants and laboratory tests on water samples obtained from the restaurants, tube wells of the city and Surma River the two main sources of water supply to the city. The test parameters were dissolved oxygen; conductance, hardness, pH, temperature, turbidity, essential and trace elements, dissolved and suspended solids and coliform bacteria. The quality of sanitary facilities and handling of food in the restaurants were also examined. It was found that the drinking water of each restaurant was contaminated with fecal coliforms and 25% restaurants had unsafe levels of iron in the water supply. Improper solid waste dumping was found as one of the reasons of groundwater pollution. Statistical analysis based on Pearson's correlation coefficient revealed significant correlation between the extent of groundwater pollution and dumping of solid waste effluents in the immediate vicinity of ground water (tube wells). It was observed that 75.69% (coefficient of determination r 2 = 0.7569) variation in the value of groundwater near the dumping place showed association with variation in the value of water quality within the dumping place. Health risk score for coliform bacteria was 1,474.77, indicating high risk. The results of the study help in enhancing awareness of health hazards of contaminated food among the consumers as well as in drawing attention of health regulatory authorities.
For the past few decades, ground water has been extensively used for the purpose of irrigation in... more For the past few decades, ground water has been extensively used for the purpose of irrigation in rural areas of Bangladesh. In areas where the ground water contaminated with arsenic (As) is used for irrigation, crops can uptake them along with other metallic nutrients. This can negatively affect the growth and overall yield of the crops which can consequently be detrimental to human health. A greenhouse study was conducted to examine the effects of arsenic-contaminated irrigation water on the growth of red amaranth (Amaranthus retroflexus L.) and uptake of arsenic. There were 13 levels of arsenic treatments (0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 and 60 mg L) mixed in irrigation water and red amaranth was grown using these irrigation water. The 1 experiment was set in RCB design with 3 replications. It has been observed that addition of arsenic with irrigation water significantly reduced the yield and yield components of red amaranth. The fresh weight of red amaranth was also reduced drastically due to the addition of more than 15 mg L level of arsenic containing 1 water. This Fresh weight decreases with the increase of arsenic concentration and the reduction ranges from 9.02 to 100.00%. Arsenic content in root, stem and leaf increases with the increase of arsenic level used. Transfer coefficient (transfer of Arsenic from soil to above ground part of plant) is highest in native arsenic (0 mg L) added red amaranth (1.60) and decrease thereafter up to 50 mg L As added red amaranth (0.35).
The separation of bitumen from mature oil sand tailings slurries was carried out in an electro-fl... more The separation of bitumen from mature oil sand tailings slurries was carried out in an electro-flotation (EF) cell equipped with titanium coated with iridium oxide (Ti-IrO 2) mesh as anode and stainless steel (SS 316) mesh as cathode. The effects of operating parameters such as pH, current density, bitumen concentration, and sodium chloride (NaCl) dosage on the performance of batch cell flotation were examined. The representative kinetics of the electro-flotation of bitumen in mature oil sand tailings slurries is best described as a first order reaction. Analysis of variance (ANOVA) is carried out to find out the statistical significance of influencing factors with respect to the first order flotation rate. The P-values in ANOVA show the order of significant factors as current density > bitumen concentration > pH. Though NaCl dosage doesn't have significant effect on flotation kinetics however it serves a significant role on reducing the power consumption of EF treatment. It is observed that at current density 150 A/m 2 , it is possible to reduce the bitumen concentration from 106.8 mg/L to less than 10 mg/L within 90 min of flotation to meet the Environmental Protection and Enhancement Act (EPEA) maximum discharge limit.
Acid Mine Drainage (AMD) is produced when sulphide-bearing mine tailings is exposed to oxygen and... more Acid Mine Drainage (AMD) is produced when sulphide-bearing mine tailings is exposed to oxygen and water and accelerated by naturally-occurring bacteria that assist in the breakdown of sulphide minerals. AMD can severely pollute surface and ground-water, as well as soils. Therefore, mine planners and managers must identify techniques that will minimize AMD impacts on life forms and their environment. In the present study, a site-specific study is carried out to assess the suitability of froth flotation for desulphurization of reactive mine tailings with an Outokumpu flotation unit, type OK0.05 at the Musselwhite Gold Mine, Northern Ontario, Canada, to prevent AMD. During froth flotation of mine tailings, a large quantity of samples must be handled and analyzed for total sulphur content with accuracy and precision. Therefore, a robust, rapid and easy digestion procedure for analysis of total sulphur in mine tailings using Inductively Coupled Plasma is also developed.
Electrochemical Advanced Oxidation Processes (eAOPs) such as the current Advanced Oxidation Syste... more Electrochemical Advanced Oxidation Processes (eAOPs) such as the current Advanced Oxidation System (AOS) are a type of electrochemical wastewater treatment that creates oxidative species, such as iodide species, chloride species, and hydroxyl radicals, that can treat even recalcitrant contaminants. It is important to determine the concentrations and locations of oxidative species in eAOPs for optimization of the wastewater treatment process. In this study, a spectrophotometric methodology was used to determine concentrations of iodide and chloride oxidative species (starting at 10, 25, and 50 ppm) within an AOS under various input voltages (6, 12, and 24 V). Overall, it was found that iodate and chlorite were the dominant species created in their respective treatments. Additionally, the concentration of iodide oxidative species increases with increasing voltage, whereas the chloride species decrease with increasing voltage. The optimal conditions for the e cient creation of AOS oxidative species were 12 V and 10 ppm potassium iodide and 6 V and 10 ppm sodium chloride, respectively. In addition, the use of iodide is recommended for wastewater treatment using the AOS to effectively create oxidative species. Following optimization, the AOS performance was tested for a synthetic stormwater. Results indicated that the AOS performed well for reduction of Eschericha coli; however, reduction of other contaminants was inconsistent as would be expected given the AOS was optimized for disinfection, not decontamination. Further AOS optimization for decontamination would lead to improved decontamination performance.
Journal of Engineering Science and Technology, 2012
The amount of rainfall received over an area is an important factor in assessing availability of ... more The amount of rainfall received over an area is an important factor in assessing availability of water to meet various demands for agriculture, industry, irrigation, generation of hydroelectricity and other human activities. The distribution of rainfall in time and space is, therefore, an important factor for the economic development of a country. Due to rapid urbanization in various parts of the north-eastern region of Bangladesh, there is a growing need to study the rainfall pattern, and also frequency of the heavy rainfall events. This study was checked monthly average rainfall from daily records of last 50 years for this region. In order to check the major events, time history of monthly rainfall data were transformed into frequency domain using the Fast Fourier Transform (FFT). Estimated peak frequency (11.98 month) depicts that major rainfall events of a year are occurring earlier than the previous year. The variability of rainfall in time scale was also checked from filtered ...
An understanding of the nature of wastewater is essential in the design and operation of collecti... more An understanding of the nature of wastewater is essential in the design and operation of collection, treatment, and disposal facilities and in the engineering management of environmental quality. Municipal wastewater of Sylhet city, divisional city of the northeastern region of Bangladesh, originates from different types of sources and then falls into the Surma River through different channels. Malni Chara, the largest channel falling into the Surma River originating from a hilly tea garden was selected for the study. In this study, physical parameters (total solids, dissolved solids, suspended solids, pH) and chemical parameters (BOD, alkalinity, DO, chlorides, nitrates, oil and grease) of wastewater were measured. Maximum value of total solids was found in the Stadium area (600mg/l). pH was found to be almost the same at every point (around 6.5). Maximum nitrates and chlorides were found in Subid Bazar (0.2 mg/L) and the Stadium area (42 mg/L) respectively. The findings of the study conclude that the quality of the wastewater of Sylhet city is medium for suspended solids, BOD 5 and chlorides, and strong for alkalinity.
ii CO-AUTHORSHIP iv ACKNOWLEDGEMENTS vii DEDICATION viii TABLE OF CONTENTS ix LIST OF TABLES xvi ... more ii CO-AUTHORSHIP iv ACKNOWLEDGEMENTS vii DEDICATION viii TABLE OF CONTENTS ix LIST OF TABLES xvi LIST OF FIGURES xviii LIST OF SYMBOLS xxv CHAPTER
We present an electrochemical advanced oxidation process (eAOP) reactor employing expanded graphi... more We present an electrochemical advanced oxidation process (eAOP) reactor employing expanded graphite, potassium iodide (KI), and electrical current, which demonstrates an exceptionally high rate of inactivation of E. coli (6log reduction in viable cells) at low current density 0.6 mA/cm^2), with low contact time (5 minutes) and low concentration of KI (10 ppm). Operando X-ray fluorescence mapping is used to show the distribution of iodine species in the reactor, and operando X-ray absorption spectroscopy in the anodic chamber reveals iodine species with higher effective oxidation state than periodate. Operando electrochemical measurements confirm the conditions in the anodic chambers are favourable for the creation of highly oxidized iodine products. The killing efficiency of this new eAOP reactor far exceeds that expected from either traditional iodine-based electrochemical water treatment or advanced oxidation systems alone, a phenomenon that may be associated with the production o...
An understanding of the nature of wastewater is essential in the design and operation of collecti... more An understanding of the nature of wastewater is essential in the design and operation of collection, treatment, and disposal facilities and in the engineering management of environmental quality. Municipal wastewater of Sylhet city, divisional city of the northeastern region of Bangladesh, originates from different types of sources and then falls into the Surma River through different channels. Malni Chara, the largest channel falling into the Surma River originating from a hilly tea garden was selected for the study. In this study, physical parameters (total solids, dissolved solids, suspended solids, pH) and chemical parameters (BOD, alkalinity, DO, chlorides, nitrates, oil and grease) of wastewater were measured. Maximum value of total solids was found in the Stadium area (600mg/l). pH was found to be almost the same at every point (around 6.5). Maximum nitrates and chlorides were found in Subid Bazar (0.2 mg/L) and the Stadium area (42 mg/L) respectively. The findings of the study conclude that the quality of the wastewater of Sylhet city is medium for suspended solids, BOD 5 and chlorides, and strong for alkalinity.
Oil sands mines generate tailings during the extraction process, which are a mixture of water, cl... more Oil sands mines generate tailings during the extraction process, which are a mixture of water, clay, sand and residual bitumen. When the tailings are released to tailings ponds, the coarse solids settle quickly, whereas fine solids containing clay minerals, namely mature fine tailings (MFT), remain suspended for years, even decades. A study is carried out to assess the suitability of electrokinetic (EK) sedimentation to accelerate sedimentation of MFT. A series of laboratory-scale column experiments are carried out to examine the effects of electrophoresis during settling processes. The investigation focuses on the effects of EK sedimentation as related to the initial solid content of the tailings suspension, applied electric field intensity, water pH, and the use of an optimized coagulant FeCl 3. Based on the experimental data, an electric field intensity of 150 V/m along with an initial tailings solid content of no N5% are the optimum condition for EK sedimentation of MFT, in terms of reducing the overall sedimentation time and increasing the final solid content. The results show that the current density of EK sedimentation for MFT should not be N 20 A/m 2 to control the bubble effect and reduce power consumption.
An understanding of the nature of wastewater is essential in the design and operation of collecti... more An understanding of the nature of wastewater is essential in the design and operation of collection, treatment, and disposal facilities and in the engineering management of environmental quality. Municipal wastewater of Sylhet city, divisional city of the northeastern region of Bangladesh, originates from different types of sources and then falls into the Surma River through different channels. Malni Chara, the largest channel falling into the Surma River originating from a hilly tea garden was selected for the study. In this study, physical parameters (total solids, dissolved solids, suspended solids, pH) and chemical parameters (BOD, alkalinity, DO, chlorides, nitrates, oil and grease) of wastewater were measured. Maximum value of total solids was found in the Stadium area (600mg/l). pH was found to be almost the same at every point (around 6.5). Maximum nitrates and chlorides were found in Subid Bazar (0.2 mg/L) and the Stadium area (42 mg/L) respectively. The findings of the study conclude that the quality of the wastewater of Sylhet city is medium for suspended solids, BOD 5 and chlorides, and strong for alkalinity. Introduction Sylhet city has been taken as our study area, which is an important divisional city located in the northeastern part of Bangladesh (Latitude: 24.857deg; N, Longitude: 91.80° E). Sylhet Municipality was established in 1878.The area of the town is 10.49 sq. km. It has a population of 285,308; density of population is 27,198 per sq km (Banglapedia, 2006). The city is situated beside the Surma River. The wastewater effluent from Sylhet city discharged to the Surma River is polluting the river water, as treatment facilities are not yet established in Sylhet. As the quality of wastewater is not satisfactory, problems like pollution of the Surma River and the streams, deterioration of the environment, and health sanitation have become serious. Obviously it is necessary to evaluate the wastewater discharge and disposal system in order to determine the effects of wastewater discharges on receiving water or the public sewer or on any proposed treatment process and to explore possible treatment process requirements to eliminate such effects. Objectives of the Study This study essentially focuses on the greater importance of analysis and design of an effective and economic rational sewage treatment system for Sylhet city. The present sewerage problems of Sylhet city set the objective of this study to characterize the combined sewage of Sylhet city, assessing the pollution level of wastewater that is discharged into the Surma River and polluting the water. Study Area This study was conducted in Sylhet city. The sewerage network of Sylhet city consists of many small drains connected with some natural hilly channels called 'Chara', which fall into the Surma River. Besides these, there are some other big natural channels, which interconnect the 'Charas'. Those natural channels are known as 'Khal'. The main 'Charas' in Sylhet city are Malni Chara, Goali Chara, Jugni Chara, and Mira Chara. Among the Khals, Khal of Mira Bazar, Khal of Niorpool, Khal of Jallar Par, Monipuri-Rajbari Khal, Khal of Taltola, and Khal of Sheikhghat are important (Alam, Nath & Siddique, 2002). The study route Malni Chara is the largest chara, which originates from Malni Chara Tea Garden and then divides into two branches. The main branch of the chara goes through a housing estate, Darga Moholla, Sylhet Stadium area, and Taltola and falls into the Surma River near Kazir Bazar. This branch of Malni Chara was selected for the study. Another branch goes through Sagar Dighir Par and the Osmani Medical College Hospital area and falls into the Surma River. Methodology Laboratory data are essential to design wastewater treatment facilities in urban areas. To obtain such data for Sylhet city, six sampling points on the main branch of Malni Chara have been selected according to their importance. …
Air-stripping method was used to remove ammonia from the wastewater collected from natural gas fe... more Air-stripping method was used to remove ammonia from the wastewater collected from natural gas fertilizer factory. Different materials were used as packing materials for the air stripping system. The effect of pH over 10.5, air-water flow ratio, nature of packing materials, height of materials and initial influent concentration of ammonia on air stripping unit were investigated. An attempt has been made to find out the stripping constant. Stripping constant was found to be .001, 0014, .001 and .0009 for coal, plastic ring, stone chips and wood chips, respectively. Best result was found for plastic ring for its higher surface area. Wood chips did not give good result, because the chips amalgamate with each other and hence reduces the surface area.
International Journal of Environmental Science and Technology, 2013
A sample preparation method of total sulphur measurement of reactive mine tailings was optimized.... more A sample preparation method of total sulphur measurement of reactive mine tailings was optimized. The total sulphur was measured by inductively coupled plasma optical emission spectroscopy, and ultrasound technique was used for sample digestion. The optimization process was adopted by a combined approach of experimental design and response surface methodology. The digestion time, temperature and acid-oxidant combination (i.e. effect of H 2 O 2 with a fixed amount of acid mixture) were investigated. A two-level and three-factor (2 3) full factorial design of experiment was applied to identify the most significant factors, and a central composite design was used to optimize the digestion procedure. KZK-1, a sericite schist, was selected as the certified reference material. The optimum methodology at 95 % confidence level (P \ 0.05) was identified to be 10 min of digestion at 77°C, with a solution of 1 ml HNO 3 :1 ml HCl:1.35 ml H 2 O 2. This combination resulted in 100 % sulphur recovery. The investigated method was verified by X-ray diffraction analysis. The optimum digestion level was applied to a reactive mine tailings, which achieved satisfactory results with a percentage relative standard deviation \ 3 %.
The physical, chemical and biological characteristics of the wastewater of Natural Gas Fertilizer... more The physical, chemical and biological characteristics of the wastewater of Natural Gas Fertilizer Factory Ltd. Fenchuganj, Sylhet were determined through extensive laboratory tests in the months of March, July, October and December of the year 2005. Concentration of Suspended Solids was within the range of 445 to 950 mg/L. Bangladesh Industrial Effluent Standards for Suspended Solids is 100 mg/L. Suspended Solids were found above the limit in all the samples. Concentration of Dissolved Solids was found to vary from 576 to 1,456 mg/L. Bangladesh Industrial Effluent Standards, for Dissolved Solids is 2,100 mg/L. Dissolved Solids were found within the limit. Concentration of BOD(5) was found to vary from 4.5 to 8.4 mg/L. Bangladesh Industrial Effluent Standards for BOD(5) is 50 mg/L. For the year 2005, the BOD(5) was found below the limit in all the samples. Dissolved Oxygen of the wastewater was found to be between 2.0 to 3.0 mg/L, which do not satisfy the standard (4.5-8 mg/L). Oil and grease concentration were found in the range of 28 to 68 mg/L, whereas the standard is 10 mg/L for discharge into the inland surface water. In 2005, concentration of Cr(+ 6) was found to vary from 0.01 to 0.156 mg/L in the wastewater. Bangladesh Industrial Effluent Standards, for Cr(+6) is 0.1 mg/L. The concentration of chromium was found above the limit in three samples. Concentration of NO(3) was found to vary from 4.5 to 15.2 mg/L in the wastewater. Bangladesh Industrial Effluent Standards for nitrate is 10 mg/L. The nitrate was found above the limit in three samples. Maximum concentration of ammonia in lagoon 1 was found 1,710 mg/L in month of December. Bangladesh Industrial Effluent Standards for ammonia nitrogen is 100 mg/L. For the year 2005, the ammonia nitrogen was found above the limit in all samples.
The oxidation of sulphidic mine tailings and consequent acid generation poses challenges for the ... more The oxidation of sulphidic mine tailings and consequent acid generation poses challenges for the environment. Accurate and precise analysis of sulphur content is necessary for impact assessment and management of mine tailings. Here, the authors aim at developing a rapid and easy digestion procedure, which may analyse and measure the total amount of sulphur in mine tailings by using inductively coupled plasma. For evaluating effects of several variables, the researchers used a univariate (analysis of variance (ANOVA)) strategy and considered factors such as composition of the acid mixture, heating time, and refluxing device to optimize the performance. To do the experiment, the researchers have used two certified reference materials (KZK-1 and RTS-2) and samples of tailings from Musselwhite mine. ANOVA result shows that heating time is the most influencing factor on acid digestion of the reference materials whereas in case of a digestion of tailings sample, hydrochloric acid proved to be the most significant parameter. Satisfactory results between the measured and referenced values are found for all experiments. It is found that the aqua regia (1 ml HNO(3) + 3 ml HCl) digestion of 0.1 g of samples after only 40 min of heating at 95°C produced fast, safe, and accurate analytical results with a recovery of 97% for the selected reference materials.
Arsenic contaminated sludge can be found from the treatment of arsenic contaminated ground water.... more Arsenic contaminated sludge can be found from the treatment of arsenic contaminated ground water. Lake of management and reuse of this sludge can create further environmental problem as there is probability of mixing with soil and water. In this paper, an effort is taken for the use of such waste. Here, effectiveness of using this sludge in making ornamental brick has been analyzed and justified. The detailed study was made upon the suitability of sludge in making bricks. Results of different tests indicate that sludge proportion is the key factor for determining the quality of ornamental bricks/tiles. The compressive strength of ornamental bricks decreases with increase of sludge proportion. This study showed that arsenic contaminated sludge could be used safely up to 4 % for making ornamental bricks. Because after that limit the quality of bricks or tiles fall markedly.
A study of the water quality conditions of Sylhet city of Bangladesh and its restaurants was carr... more A study of the water quality conditions of Sylhet city of Bangladesh and its restaurants was carried out to assess risks to human health. The investigation was based on questionnaire survey of restaurants and laboratory tests on water samples obtained from the restaurants, tube wells of the city and Surma River the two main sources of water supply to the city. The test parameters were dissolved oxygen; conductance, hardness, pH, temperature, turbidity, essential and trace elements, dissolved and suspended solids and coliform bacteria. The quality of sanitary facilities and handling of food in the restaurants were also examined. It was found that the drinking water of each restaurant was contaminated with fecal coliforms and 25% restaurants had unsafe levels of iron in the water supply. Improper solid waste dumping was found as one of the reasons of groundwater pollution. Statistical analysis based on Pearson's correlation coefficient revealed significant correlation between the extent of groundwater pollution and dumping of solid waste effluents in the immediate vicinity of ground water (tube wells). It was observed that 75.69% (coefficient of determination r 2 = 0.7569) variation in the value of groundwater near the dumping place showed association with variation in the value of water quality within the dumping place. Health risk score for coliform bacteria was 1,474.77, indicating high risk. The results of the study help in enhancing awareness of health hazards of contaminated food among the consumers as well as in drawing attention of health regulatory authorities.
For the past few decades, ground water has been extensively used for the purpose of irrigation in... more For the past few decades, ground water has been extensively used for the purpose of irrigation in rural areas of Bangladesh. In areas where the ground water contaminated with arsenic (As) is used for irrigation, crops can uptake them along with other metallic nutrients. This can negatively affect the growth and overall yield of the crops which can consequently be detrimental to human health. A greenhouse study was conducted to examine the effects of arsenic-contaminated irrigation water on the growth of red amaranth (Amaranthus retroflexus L.) and uptake of arsenic. There were 13 levels of arsenic treatments (0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 and 60 mg L) mixed in irrigation water and red amaranth was grown using these irrigation water. The 1 experiment was set in RCB design with 3 replications. It has been observed that addition of arsenic with irrigation water significantly reduced the yield and yield components of red amaranth. The fresh weight of red amaranth was also reduced drastically due to the addition of more than 15 mg L level of arsenic containing 1 water. This Fresh weight decreases with the increase of arsenic concentration and the reduction ranges from 9.02 to 100.00%. Arsenic content in root, stem and leaf increases with the increase of arsenic level used. Transfer coefficient (transfer of Arsenic from soil to above ground part of plant) is highest in native arsenic (0 mg L) added red amaranth (1.60) and decrease thereafter up to 50 mg L As added red amaranth (0.35).
The separation of bitumen from mature oil sand tailings slurries was carried out in an electro-fl... more The separation of bitumen from mature oil sand tailings slurries was carried out in an electro-flotation (EF) cell equipped with titanium coated with iridium oxide (Ti-IrO 2) mesh as anode and stainless steel (SS 316) mesh as cathode. The effects of operating parameters such as pH, current density, bitumen concentration, and sodium chloride (NaCl) dosage on the performance of batch cell flotation were examined. The representative kinetics of the electro-flotation of bitumen in mature oil sand tailings slurries is best described as a first order reaction. Analysis of variance (ANOVA) is carried out to find out the statistical significance of influencing factors with respect to the first order flotation rate. The P-values in ANOVA show the order of significant factors as current density > bitumen concentration > pH. Though NaCl dosage doesn't have significant effect on flotation kinetics however it serves a significant role on reducing the power consumption of EF treatment. It is observed that at current density 150 A/m 2 , it is possible to reduce the bitumen concentration from 106.8 mg/L to less than 10 mg/L within 90 min of flotation to meet the Environmental Protection and Enhancement Act (EPEA) maximum discharge limit.
Acid Mine Drainage (AMD) is produced when sulphide-bearing mine tailings is exposed to oxygen and... more Acid Mine Drainage (AMD) is produced when sulphide-bearing mine tailings is exposed to oxygen and water and accelerated by naturally-occurring bacteria that assist in the breakdown of sulphide minerals. AMD can severely pollute surface and ground-water, as well as soils. Therefore, mine planners and managers must identify techniques that will minimize AMD impacts on life forms and their environment. In the present study, a site-specific study is carried out to assess the suitability of froth flotation for desulphurization of reactive mine tailings with an Outokumpu flotation unit, type OK0.05 at the Musselwhite Gold Mine, Northern Ontario, Canada, to prevent AMD. During froth flotation of mine tailings, a large quantity of samples must be handled and analyzed for total sulphur content with accuracy and precision. Therefore, a robust, rapid and easy digestion procedure for analysis of total sulphur in mine tailings using Inductively Coupled Plasma is also developed.
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