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 ...
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. 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. …
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.
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.
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 ...
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. 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. …
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.
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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