Abstract The absence or lack of effective stakeholder engagement during project life cycle, espec... more Abstract The absence or lack of effective stakeholder engagement during project life cycle, especially at the earlier stages of planning and implementation often negatively impacts the expected performance of projects. These coupled consequences of the lack of contextual knowledge from the stakeholders as well as lack of their support in the field necessitates effective stakeholder engagement. However, this integration faces challenges such as limitations of project resources and conflicting interests of the stakeholders. In this sense, project resources can be allocated based on the priorities of the fields of conflicts to facilitate stakeholder engagement of the projects. The goal of this paper is to provide a framework to enhance effectiveness of the stakeholder engagement in projects by systematically ranking the potential conflicts while combining the viewpoints of stakeholders and project management team. For this purpose, we draw on stakeholder theory, value-based management, matrix-based dependency modeling, and Total Quality Management to develop a stakeholder engagement framework while considering fuzzy inputs for reflecting the ambiguities at the project life cycle. The proposed approach is then applied to plan stakeholder engagement in case of a green building project in Iran. Practically, application of the proposed framework facilitates stakeholder engagement for project managers in line with sustainable goals through early assessment of the fields of potential conflicts of interests.
The Science of the total environment, Jan 15, 2014
Dissolved organic carbon (DOC) is a recognized indicator of natural organic matter (NOM) in surfa... more Dissolved organic carbon (DOC) is a recognized indicator of natural organic matter (NOM) in surface waters. The aim of this paper is twofold: to evaluate the impact of geophysical characteristics, climate and ecological zones on DOC concentrations in surface waters and, to develop a statistical model to estimate the regional variability of these concentrations. In this study, multilevel statistical analysis was used to achieve three specific objectives: (1) evaluate the influence of climate and geophysical characteristics on DOC concentrations in surface waters; (2) compare the influence of geophysical characteristics and ecological zones on DOC concentrations in surface waters; and (3) develop a model to estimate the most accurate DOC concentrations in surface waters. The case study involved 115 catchments from surface waters in the Province of Quebec, Canada. Results showed that mean temperatures recorded 60 days prior to sampling, total precipitation 10 days prior to sampling and...
Stochastic Environmental Research and Risk Assessment, 2007
Environmental indices (EI) are common communication tool used to describe the overall status of e... more Environmental indices (EI) are common communication tool used to describe the overall status of environmental systems (e.g. air, water, soil). Development of EI entails the use of mathematical operators to aggregate various non-commensurate input parameters in a logical manner. Ordered weighted averaging (OWA) operator is a general mean type operator that provides flexibility in the aggregation process such that the aggregated value is bounded between minimum and maximum values of the input parameters. This flexibility of OWA operator is realized through the concept of orness, which is a surrogate for decision maker's attitude. For the development of environmental indices, the type of input parameters also affects the choice of aggregation operators. If the input parameters are linguistic or fuzzy, the aggregation through OWA operators is not possible, and the use of fuzzy arithmetic is warranted. To develop EI, the concept of FN-OWA (fuzzy number OWA) operators is explored to handle the situations when one ore more input parameter has fuzzy (or linguistic) values. The proposed approach is demonstrated using data provided in an earlier study by Swamee and Tyagi (2000) for establishing water quality indices. Multiple hypothetical scenarios are also generated to highlight the utility and the sensitivity of the proposed approach.
The main objective of this study is to evaluate and predict the performance of slow sand filters ... more The main objective of this study is to evaluate and predict the performance of slow sand filters used for wastewater treatment. The uncertainties in the control parameters and processes require fuzzy sets to be used when modelling system performance. Fuzzy logic if-then rules were used to build a model for the removal efficiency (total coliforms) of slow sand filters. The data were collected from three pilotscale slow sand filters at the Alkhobar (Saudi Arabia) wastewater treatment plant. The removal efficiency of filters was modelled using three input control parameters-filtration rate, sand bed depth and grain size. Based on available data, fuzzy logic if-then rules were established. The fuzzy rule-based model was validated using experimental data of three case studies reported in the literature. The results were also compared with a multiple regression model. A possibilistic risk analysis was performed using optimal removal efficiency of the slow sand filters. The risk is estimated with respect to noncompliance of unrestricted agricultural reuse standards (100 total coliform/100 ml). In addition to slow sand filters, post-or pre-chlorination of wastewater is recommended to improve wastewater quality for conforming agricultural reuse standards. Crown
The pressure acid leach process is the most widely used method of metal extraction from laterite ... more The pressure acid leach process is the most widely used method of metal extraction from laterite ores. The self-weight settling rate of the ore slurries governs the throughput of the process and is improved by adding synthetic polymers. The charge density, molecular weight, and dosage of the polymers are the key factors influencing the settling rate of the slurries. This interdisciplinary paper uses the geotechnical understanding of hindered sedimentation for a mining engineering application. A conceptual fuzzy rule-based model was developed to evaluate the initial hydraulic conductivity of polymer-modified laterite ore slurries. Identification of control parameters and selection of the model architecture (fuzzy rule-base) were based on expert judgment. The developed model was trained and validated using bench-scale settling test data. The model reasonably predicts the initial hydraulic conductivity of polymer-added laterite ore slurry with a coefficient of determination of 0.75. Rank correlation coefficient-based sensitivity analyses indicated that charge density was the most significant polymer parameter followed by molecular weight and then by dosage. Charge density accounted for more than 97% of variability in the initial hydraulic conductivity estimates for both anionic and cationic polymers.
With an increasing emphasis on network security, much more attention has been attracted to the vu... more With an increasing emphasis on network security, much more attention has been attracted to the vulnerability of complex networks. The multi-scale evaluation of vulnerability is widely used since it makes use of combined powers of the links' betweenness and has an effective evaluation to vulnerability. However, how to determine the coefficient in existing multi-scale evaluation model to measure the vulnerability of different networks is still an open issue. In this paper, an improved model based on the fractal dimension of complex networks is proposed to obtain a more reasonable evaluation of vulnerability with more physical significance. Not only the structure and basic physical properties of networks is characterized, but also the covering ability of networks, which is related to the vulnerability of the network, is taken into consideration in our proposed method. The numerical examples
How to express an expert's or a decision maker's preference for alternatives is an open issue. Co... more How to express an expert's or a decision maker's preference for alternatives is an open issue. Consistent fuzzy preference relation (CFPR) is with big advantages to handle this problem due to it can be construed via a smaller number of pairwise comparisons and satisfies additive transitivity property. However, the CFPR is incapable of dealing with the cases involving uncertain and incomplete information. In this paper, a D numbers extended consistent fuzzy preference relation (D-CFPR) is proposed to overcome the weakness. The D-CFPR extends the classical CFPR by using a new model of expressing uncertain information called D numbers. The D-CFPR inherits the merits of classical CFPR and can be totally reduced to the classical CFPR. This
Chlorine is the most commonly used disinfectant for watertreatment but when in contact with organ... more Chlorine is the most commonly used disinfectant for watertreatment but when in contact with organic precursors it producestoxic compounds known as trihalomethanes (THMs). Chloroform isthe most commonly occurring THM and constitutes approximately90% of the THM concentration. A study was conducted inNewfoundland for estimating the chloroform content in thedrinking water supplies in Clarenville and St. John's. Thesampling program was conducted in
Abu Dhabi International Petroleum Conference and Exhibition, 2012
Egypt is located in the Northeast of Africa where oil and gas (O&G) are produced offshore from th... more Egypt is located in the Northeast of Africa where oil and gas (O&G) are produced offshore from the Gulf of Suez and the Southeast part of the Mediterranean. The O&G production in Egypt is distributed as follows: 70% Gulf of Suez, 16% Western desert, 8% Sinai Peninsula and 6% Eastern desert. Past O&G activities, refining and transport have resulted in chronic pollution in Egyptian offshore, and numerous environmental programs have been initiated to protect new development areas from the environmental impacts. The offshore drilling process uses drilling fluids (muds) and generates waste fluids and cuttings, which could be the largest discharges going into the receiving water bodies. Water-based drilling fluids are commonly employed for drilling in Egyptian offshore because of their expected environmental benign behavior in the marine environment. The main objective of this paper is to highlight relevant Egyptian environmental regulations and explain several options to manage offshore ...
Stochastic Environmental Research and Risk Assessment, 2012
Abstract Egypt is located in the Northeast of Africa where oil and gas (O&G) are prod... more Abstract Egypt is located in the Northeast of Africa where oil and gas (O&G) are produced offshore from the Gulf of Suez and the Southeast part of the Mediterranean. The O&G production in Egypt is distributed as follows: 70% from Gulf of Suez, 16% from Western desert, 8% from the Sinai Peninsula and 6% from Eastern desert. Past O&G activities, refining and transport have resulted in chronic pollution in Egyptian offshore and numerous environmental programs have been initiated to protect new development areas from the ...
Due to the hydrophobic nature of synthetic based fluids (SBFs), drilling cuttings are not very di... more Due to the hydrophobic nature of synthetic based fluids (SBFs), drilling cuttings are not very dispersive in the water column and settle down close to the disposal site. Arsenic and copper are two important toxic heavy metals, among others, found in the drilling waste. In this article, the concentrations of heavy metals are determined using a steady state "aquivalence-based" fate model in a probabilistic mode. Monte Carlo simulations are employed to determine pore water concentrations. A hypothetical case study is used to determine the water quality impacts for two discharge options: 4% and 10% attached SBFs, which correspond to the best available technology option and the current discharge practice in the U.S. offshore. The exposure concentration (CE) is a predicted environmental concentration, which is adjusted for exposure probability and bioavailable fraction of heavy metals. The response of the ecosystem (RE) is defined by developing an empirical distribution function of predicted no-effect concentration. The pollutants' pore water concentrations within the radius of 750 m are estimated and cumulative distributions of risk quotient (RQ=CE/RE) are developed to determine the probability of RQ greater than 1.
Quantitative risk analysis (QRA) is a systematic approach for evaluating likelihood, consequences... more Quantitative risk analysis (QRA) is a systematic approach for evaluating likelihood, consequences, and risk of adverse events. QRA based on event (ETA) and fault tree analyses (FTA) employs two basic assumptions. The first assumption is related to likelihood values of input events, and the second assumption is regarding interdependence among the events (for ETA) or basic events (for FTA). Traditionally, FTA and ETA both use crisp probabilities; however, to deal with uncertainties, the probability distributions of input event likelihoods are assumed. These probability distributions are often hard to come by and even if available, they are subject to incompleteness (partial ignorance) and imprecision. Furthermore, both FTA and ETA assume that events (or basic events) are independent. In practice, these two assumptions are often unrealistic. This article focuses on handling uncertainty in a QRA framework of a process system. Fuzzy set theory and evidence theory are used to describe the uncertainties in the input event likelihoods. A method based on a dependency coefficient is used to express interdependencies of events (or basic events) in ETA and FTA. To demonstrate the approach, two case studies are discussed.
Event tree analysis (ETA) is an established risk analysis technique to assess likelihood (in a pr... more Event tree analysis (ETA) is an established risk analysis technique to assess likelihood (in a probabilistic context) of an accident. The objective data available to estimate the likelihood is often missing (or sparse), and even if available, is subject to incompleteness (partial ignorance) and imprecision (vagueness). Without addressing incompleteness and imprecision in the available data, ETA and subsequent risk analysis
A bow-tie diagram combines a fault tree and an event tree to represent the risk control parameter... more A bow-tie diagram combines a fault tree and an event tree to represent the risk control parameters on a common platform for mitigating an accident. Quantitative analysis of a bow-tie is still a major challenge since it follows the traditional assumptions of fault and event tree analyses. The assumptions consider the crisp probabilities and "independent" relationships for the input events. The crisp probabilities for the input events are often missing or hard to come by, which introduces data uncertainty. The assumption of "independence" introduces model uncertainty. Elicitation of expert's knowledge for the missing data may provide an alternative; however, such knowledge incorporates uncertainties and may undermine the credibility of risk analysis. This paper attempts to accommodate the expert's knowledge to overcome missing data and incorporate fuzzy set and evidence theory to assess the uncertainties. Further, dependency coefficient-based fuzzy and evidence theory approaches have been developed to address the model uncertainty for bow-tie analysis. In addition, a method of sensitivity analysis is proposed to predict the most contributing input events in the bow-tie analysis. To demonstrate the utility of the approaches in industrial application, a bow-tie diagram of the BP Texas City accident is developed and analyzed.
Many studies have been carried out in the past to provide solutions to the threat of chemicals to... more Many studies have been carried out in the past to provide solutions to the threat of chemicals to the ecosystem. However, the basic scientific capability to predict the risk of adverse effects on the ecological system has not kept pace with society's increasing demand for uses of chemicals. As a scientific methodology for quantifying the risk to the environment associated with exposure to chemicals, ecological risk assessment is increasingly important in environmental problem solving. The purpose of this paper is to present a methodology for ...
In order to handle uncertain information, this paper proposes evidential cognitive maps (ECMs), s... more In order to handle uncertain information, this paper proposes evidential cognitive maps (ECMs), similar to the fuzzy cognitive maps (FCMs). ECMs are uncertain-graph structures for representing causal reasoning through the combination of cognitive maps and Dempster Shafer evidence theory. The framework of ECMs is developed in detail and an application to socioeconomic model is used to illustrate the application of the proposed methodology.
Journal of Loss Prevention in the Process Industries, 2012
Bow-tie analysis is a fairly new concept in risk assessment that can describe the relationships a... more Bow-tie analysis is a fairly new concept in risk assessment that can describe the relationships among different risk control parameters, such as causes, hazards and consequences to mitigate the likelihood of occurrence of unwanted events in an industrial system. It also facilitates the performance of quantitative risk analysis for an unwanted event providing a detailed investigation starting from basic causes to final consequences. The credibility of quantitative evaluation of the bow-tie is still a major concern since uncertainty, due to limited or missing data, often restricts the performance of analysis. The utilization of expert knowledge often provides an alternative for such a situation. However, it comes at the cost of possible uncertainties related to incompleteness (partial ignorance), imprecision (subjectivity), and lack of consensus (if multiple expert judgments are used). Further, if the bow-tie analysis is not flexible enough to incorporate new knowledge or evidence, it may undermine the purpose of risk assessment. Fuzzy set and evidence theory are capable of characterizing the uncertainty associated with expert knowledge. To minimize the overall uncertainty, fusing the knowledge of multiple experts and updating prior knowledge with new evidence are equally important in addition to addressing the uncertainties in the knowledge. This paper proposes a methodology to characterize the uncertainties, aggregate knowledge and update prior knowledge or evidence, if new data become available for the bow-tie analysis. A case study comprising a bow-tie for a typical offshore process facility has also been developed to describe the utility of this methodology in an industrial environment.
International Journal of Environmental Studies, 2003
Drilling muds or fluids used in drilling operations serve several functions: they lubricate the d... more Drilling muds or fluids used in drilling operations serve several functions: they lubricate the drill bit; maintain borehole pressure; clean and condition the hole; and flush rock cuttings to the surface. Drilling mud also adheres to rock cuttings, as can formation oil. Barite is used as a weighting agent, which approximately makes up approximately 33% of synthetic mud. It contains traces of heavy metals, which contribute to the toxicity of drilling waste. As environmental issues attract increasing public awareness, the treatment and disposal of ...
Human and Ecological Risk Assessment: An International Journal, 2004
Human health effects from naturally occurring radioactive materials (NORM) in produced water are ... more Human health effects from naturally occurring radioactive materials (NORM) in produced water are of concern due to their bioavailability and bioaccumulation characteristics in finfish and shellfish species used for human consumption. Being chemically similar to calcium, radium concentrates mostly in bones, shells and exoskeletons. Previous studies have been based on the whole-body bioaccumulation of radium in fish where the distribution of radium in bone/exoskeleton and the edible parts of fish were not considered separately and thus the predicted risks were relatively high. In this paper, the distribution of radium in the non-edible and edible parts of fish and the probability of exposure to a produced water plume have been studied in order to characterize human health risks. A probabilistic hydrodynamic model has been incorporated in this study. Using the concentration distribution approach, the mean cancer risks to humans were predicted in the range of 8.6×10-7 to 9.5×10-7 , which were 2.6 to 2.7 times less than the risks predicted by using the whole body concentrations. The exceedence probability of maximum permissible human health cancer risk of 1×10-4 is close to zero. At a risk level of 1×10-6 , the exceedence probability is 21% while in the whole body concentration approach it is between 45 to 49%. In this study, no effect on fish from exposure to NORM components in produced water was found.
Abstract The absence or lack of effective stakeholder engagement during project life cycle, espec... more Abstract The absence or lack of effective stakeholder engagement during project life cycle, especially at the earlier stages of planning and implementation often negatively impacts the expected performance of projects. These coupled consequences of the lack of contextual knowledge from the stakeholders as well as lack of their support in the field necessitates effective stakeholder engagement. However, this integration faces challenges such as limitations of project resources and conflicting interests of the stakeholders. In this sense, project resources can be allocated based on the priorities of the fields of conflicts to facilitate stakeholder engagement of the projects. The goal of this paper is to provide a framework to enhance effectiveness of the stakeholder engagement in projects by systematically ranking the potential conflicts while combining the viewpoints of stakeholders and project management team. For this purpose, we draw on stakeholder theory, value-based management, matrix-based dependency modeling, and Total Quality Management to develop a stakeholder engagement framework while considering fuzzy inputs for reflecting the ambiguities at the project life cycle. The proposed approach is then applied to plan stakeholder engagement in case of a green building project in Iran. Practically, application of the proposed framework facilitates stakeholder engagement for project managers in line with sustainable goals through early assessment of the fields of potential conflicts of interests.
The Science of the total environment, Jan 15, 2014
Dissolved organic carbon (DOC) is a recognized indicator of natural organic matter (NOM) in surfa... more Dissolved organic carbon (DOC) is a recognized indicator of natural organic matter (NOM) in surface waters. The aim of this paper is twofold: to evaluate the impact of geophysical characteristics, climate and ecological zones on DOC concentrations in surface waters and, to develop a statistical model to estimate the regional variability of these concentrations. In this study, multilevel statistical analysis was used to achieve three specific objectives: (1) evaluate the influence of climate and geophysical characteristics on DOC concentrations in surface waters; (2) compare the influence of geophysical characteristics and ecological zones on DOC concentrations in surface waters; and (3) develop a model to estimate the most accurate DOC concentrations in surface waters. The case study involved 115 catchments from surface waters in the Province of Quebec, Canada. Results showed that mean temperatures recorded 60 days prior to sampling, total precipitation 10 days prior to sampling and...
Stochastic Environmental Research and Risk Assessment, 2007
Environmental indices (EI) are common communication tool used to describe the overall status of e... more Environmental indices (EI) are common communication tool used to describe the overall status of environmental systems (e.g. air, water, soil). Development of EI entails the use of mathematical operators to aggregate various non-commensurate input parameters in a logical manner. Ordered weighted averaging (OWA) operator is a general mean type operator that provides flexibility in the aggregation process such that the aggregated value is bounded between minimum and maximum values of the input parameters. This flexibility of OWA operator is realized through the concept of orness, which is a surrogate for decision maker's attitude. For the development of environmental indices, the type of input parameters also affects the choice of aggregation operators. If the input parameters are linguistic or fuzzy, the aggregation through OWA operators is not possible, and the use of fuzzy arithmetic is warranted. To develop EI, the concept of FN-OWA (fuzzy number OWA) operators is explored to handle the situations when one ore more input parameter has fuzzy (or linguistic) values. The proposed approach is demonstrated using data provided in an earlier study by Swamee and Tyagi (2000) for establishing water quality indices. Multiple hypothetical scenarios are also generated to highlight the utility and the sensitivity of the proposed approach.
The main objective of this study is to evaluate and predict the performance of slow sand filters ... more The main objective of this study is to evaluate and predict the performance of slow sand filters used for wastewater treatment. The uncertainties in the control parameters and processes require fuzzy sets to be used when modelling system performance. Fuzzy logic if-then rules were used to build a model for the removal efficiency (total coliforms) of slow sand filters. The data were collected from three pilotscale slow sand filters at the Alkhobar (Saudi Arabia) wastewater treatment plant. The removal efficiency of filters was modelled using three input control parameters-filtration rate, sand bed depth and grain size. Based on available data, fuzzy logic if-then rules were established. The fuzzy rule-based model was validated using experimental data of three case studies reported in the literature. The results were also compared with a multiple regression model. A possibilistic risk analysis was performed using optimal removal efficiency of the slow sand filters. The risk is estimated with respect to noncompliance of unrestricted agricultural reuse standards (100 total coliform/100 ml). In addition to slow sand filters, post-or pre-chlorination of wastewater is recommended to improve wastewater quality for conforming agricultural reuse standards. Crown
The pressure acid leach process is the most widely used method of metal extraction from laterite ... more The pressure acid leach process is the most widely used method of metal extraction from laterite ores. The self-weight settling rate of the ore slurries governs the throughput of the process and is improved by adding synthetic polymers. The charge density, molecular weight, and dosage of the polymers are the key factors influencing the settling rate of the slurries. This interdisciplinary paper uses the geotechnical understanding of hindered sedimentation for a mining engineering application. A conceptual fuzzy rule-based model was developed to evaluate the initial hydraulic conductivity of polymer-modified laterite ore slurries. Identification of control parameters and selection of the model architecture (fuzzy rule-base) were based on expert judgment. The developed model was trained and validated using bench-scale settling test data. The model reasonably predicts the initial hydraulic conductivity of polymer-added laterite ore slurry with a coefficient of determination of 0.75. Rank correlation coefficient-based sensitivity analyses indicated that charge density was the most significant polymer parameter followed by molecular weight and then by dosage. Charge density accounted for more than 97% of variability in the initial hydraulic conductivity estimates for both anionic and cationic polymers.
With an increasing emphasis on network security, much more attention has been attracted to the vu... more With an increasing emphasis on network security, much more attention has been attracted to the vulnerability of complex networks. The multi-scale evaluation of vulnerability is widely used since it makes use of combined powers of the links' betweenness and has an effective evaluation to vulnerability. However, how to determine the coefficient in existing multi-scale evaluation model to measure the vulnerability of different networks is still an open issue. In this paper, an improved model based on the fractal dimension of complex networks is proposed to obtain a more reasonable evaluation of vulnerability with more physical significance. Not only the structure and basic physical properties of networks is characterized, but also the covering ability of networks, which is related to the vulnerability of the network, is taken into consideration in our proposed method. The numerical examples
How to express an expert's or a decision maker's preference for alternatives is an open issue. Co... more How to express an expert's or a decision maker's preference for alternatives is an open issue. Consistent fuzzy preference relation (CFPR) is with big advantages to handle this problem due to it can be construed via a smaller number of pairwise comparisons and satisfies additive transitivity property. However, the CFPR is incapable of dealing with the cases involving uncertain and incomplete information. In this paper, a D numbers extended consistent fuzzy preference relation (D-CFPR) is proposed to overcome the weakness. The D-CFPR extends the classical CFPR by using a new model of expressing uncertain information called D numbers. The D-CFPR inherits the merits of classical CFPR and can be totally reduced to the classical CFPR. This
Chlorine is the most commonly used disinfectant for watertreatment but when in contact with organ... more Chlorine is the most commonly used disinfectant for watertreatment but when in contact with organic precursors it producestoxic compounds known as trihalomethanes (THMs). Chloroform isthe most commonly occurring THM and constitutes approximately90% of the THM concentration. A study was conducted inNewfoundland for estimating the chloroform content in thedrinking water supplies in Clarenville and St. John's. Thesampling program was conducted in
Abu Dhabi International Petroleum Conference and Exhibition, 2012
Egypt is located in the Northeast of Africa where oil and gas (O&G) are produced offshore from th... more Egypt is located in the Northeast of Africa where oil and gas (O&G) are produced offshore from the Gulf of Suez and the Southeast part of the Mediterranean. The O&G production in Egypt is distributed as follows: 70% Gulf of Suez, 16% Western desert, 8% Sinai Peninsula and 6% Eastern desert. Past O&G activities, refining and transport have resulted in chronic pollution in Egyptian offshore, and numerous environmental programs have been initiated to protect new development areas from the environmental impacts. The offshore drilling process uses drilling fluids (muds) and generates waste fluids and cuttings, which could be the largest discharges going into the receiving water bodies. Water-based drilling fluids are commonly employed for drilling in Egyptian offshore because of their expected environmental benign behavior in the marine environment. The main objective of this paper is to highlight relevant Egyptian environmental regulations and explain several options to manage offshore ...
Stochastic Environmental Research and Risk Assessment, 2012
Abstract Egypt is located in the Northeast of Africa where oil and gas (O&G) are prod... more Abstract Egypt is located in the Northeast of Africa where oil and gas (O&G) are produced offshore from the Gulf of Suez and the Southeast part of the Mediterranean. The O&G production in Egypt is distributed as follows: 70% from Gulf of Suez, 16% from Western desert, 8% from the Sinai Peninsula and 6% from Eastern desert. Past O&G activities, refining and transport have resulted in chronic pollution in Egyptian offshore and numerous environmental programs have been initiated to protect new development areas from the ...
Due to the hydrophobic nature of synthetic based fluids (SBFs), drilling cuttings are not very di... more Due to the hydrophobic nature of synthetic based fluids (SBFs), drilling cuttings are not very dispersive in the water column and settle down close to the disposal site. Arsenic and copper are two important toxic heavy metals, among others, found in the drilling waste. In this article, the concentrations of heavy metals are determined using a steady state "aquivalence-based" fate model in a probabilistic mode. Monte Carlo simulations are employed to determine pore water concentrations. A hypothetical case study is used to determine the water quality impacts for two discharge options: 4% and 10% attached SBFs, which correspond to the best available technology option and the current discharge practice in the U.S. offshore. The exposure concentration (CE) is a predicted environmental concentration, which is adjusted for exposure probability and bioavailable fraction of heavy metals. The response of the ecosystem (RE) is defined by developing an empirical distribution function of predicted no-effect concentration. The pollutants' pore water concentrations within the radius of 750 m are estimated and cumulative distributions of risk quotient (RQ=CE/RE) are developed to determine the probability of RQ greater than 1.
Quantitative risk analysis (QRA) is a systematic approach for evaluating likelihood, consequences... more Quantitative risk analysis (QRA) is a systematic approach for evaluating likelihood, consequences, and risk of adverse events. QRA based on event (ETA) and fault tree analyses (FTA) employs two basic assumptions. The first assumption is related to likelihood values of input events, and the second assumption is regarding interdependence among the events (for ETA) or basic events (for FTA). Traditionally, FTA and ETA both use crisp probabilities; however, to deal with uncertainties, the probability distributions of input event likelihoods are assumed. These probability distributions are often hard to come by and even if available, they are subject to incompleteness (partial ignorance) and imprecision. Furthermore, both FTA and ETA assume that events (or basic events) are independent. In practice, these two assumptions are often unrealistic. This article focuses on handling uncertainty in a QRA framework of a process system. Fuzzy set theory and evidence theory are used to describe the uncertainties in the input event likelihoods. A method based on a dependency coefficient is used to express interdependencies of events (or basic events) in ETA and FTA. To demonstrate the approach, two case studies are discussed.
Event tree analysis (ETA) is an established risk analysis technique to assess likelihood (in a pr... more Event tree analysis (ETA) is an established risk analysis technique to assess likelihood (in a probabilistic context) of an accident. The objective data available to estimate the likelihood is often missing (or sparse), and even if available, is subject to incompleteness (partial ignorance) and imprecision (vagueness). Without addressing incompleteness and imprecision in the available data, ETA and subsequent risk analysis
A bow-tie diagram combines a fault tree and an event tree to represent the risk control parameter... more A bow-tie diagram combines a fault tree and an event tree to represent the risk control parameters on a common platform for mitigating an accident. Quantitative analysis of a bow-tie is still a major challenge since it follows the traditional assumptions of fault and event tree analyses. The assumptions consider the crisp probabilities and "independent" relationships for the input events. The crisp probabilities for the input events are often missing or hard to come by, which introduces data uncertainty. The assumption of "independence" introduces model uncertainty. Elicitation of expert's knowledge for the missing data may provide an alternative; however, such knowledge incorporates uncertainties and may undermine the credibility of risk analysis. This paper attempts to accommodate the expert's knowledge to overcome missing data and incorporate fuzzy set and evidence theory to assess the uncertainties. Further, dependency coefficient-based fuzzy and evidence theory approaches have been developed to address the model uncertainty for bow-tie analysis. In addition, a method of sensitivity analysis is proposed to predict the most contributing input events in the bow-tie analysis. To demonstrate the utility of the approaches in industrial application, a bow-tie diagram of the BP Texas City accident is developed and analyzed.
Many studies have been carried out in the past to provide solutions to the threat of chemicals to... more Many studies have been carried out in the past to provide solutions to the threat of chemicals to the ecosystem. However, the basic scientific capability to predict the risk of adverse effects on the ecological system has not kept pace with society's increasing demand for uses of chemicals. As a scientific methodology for quantifying the risk to the environment associated with exposure to chemicals, ecological risk assessment is increasingly important in environmental problem solving. The purpose of this paper is to present a methodology for ...
In order to handle uncertain information, this paper proposes evidential cognitive maps (ECMs), s... more In order to handle uncertain information, this paper proposes evidential cognitive maps (ECMs), similar to the fuzzy cognitive maps (FCMs). ECMs are uncertain-graph structures for representing causal reasoning through the combination of cognitive maps and Dempster Shafer evidence theory. The framework of ECMs is developed in detail and an application to socioeconomic model is used to illustrate the application of the proposed methodology.
Journal of Loss Prevention in the Process Industries, 2012
Bow-tie analysis is a fairly new concept in risk assessment that can describe the relationships a... more Bow-tie analysis is a fairly new concept in risk assessment that can describe the relationships among different risk control parameters, such as causes, hazards and consequences to mitigate the likelihood of occurrence of unwanted events in an industrial system. It also facilitates the performance of quantitative risk analysis for an unwanted event providing a detailed investigation starting from basic causes to final consequences. The credibility of quantitative evaluation of the bow-tie is still a major concern since uncertainty, due to limited or missing data, often restricts the performance of analysis. The utilization of expert knowledge often provides an alternative for such a situation. However, it comes at the cost of possible uncertainties related to incompleteness (partial ignorance), imprecision (subjectivity), and lack of consensus (if multiple expert judgments are used). Further, if the bow-tie analysis is not flexible enough to incorporate new knowledge or evidence, it may undermine the purpose of risk assessment. Fuzzy set and evidence theory are capable of characterizing the uncertainty associated with expert knowledge. To minimize the overall uncertainty, fusing the knowledge of multiple experts and updating prior knowledge with new evidence are equally important in addition to addressing the uncertainties in the knowledge. This paper proposes a methodology to characterize the uncertainties, aggregate knowledge and update prior knowledge or evidence, if new data become available for the bow-tie analysis. A case study comprising a bow-tie for a typical offshore process facility has also been developed to describe the utility of this methodology in an industrial environment.
International Journal of Environmental Studies, 2003
Drilling muds or fluids used in drilling operations serve several functions: they lubricate the d... more Drilling muds or fluids used in drilling operations serve several functions: they lubricate the drill bit; maintain borehole pressure; clean and condition the hole; and flush rock cuttings to the surface. Drilling mud also adheres to rock cuttings, as can formation oil. Barite is used as a weighting agent, which approximately makes up approximately 33% of synthetic mud. It contains traces of heavy metals, which contribute to the toxicity of drilling waste. As environmental issues attract increasing public awareness, the treatment and disposal of ...
Human and Ecological Risk Assessment: An International Journal, 2004
Human health effects from naturally occurring radioactive materials (NORM) in produced water are ... more Human health effects from naturally occurring radioactive materials (NORM) in produced water are of concern due to their bioavailability and bioaccumulation characteristics in finfish and shellfish species used for human consumption. Being chemically similar to calcium, radium concentrates mostly in bones, shells and exoskeletons. Previous studies have been based on the whole-body bioaccumulation of radium in fish where the distribution of radium in bone/exoskeleton and the edible parts of fish were not considered separately and thus the predicted risks were relatively high. In this paper, the distribution of radium in the non-edible and edible parts of fish and the probability of exposure to a produced water plume have been studied in order to characterize human health risks. A probabilistic hydrodynamic model has been incorporated in this study. Using the concentration distribution approach, the mean cancer risks to humans were predicted in the range of 8.6×10-7 to 9.5×10-7 , which were 2.6 to 2.7 times less than the risks predicted by using the whole body concentrations. The exceedence probability of maximum permissible human health cancer risk of 1×10-4 is close to zero. At a risk level of 1×10-6 , the exceedence probability is 21% while in the whole body concentration approach it is between 45 to 49%. In this study, no effect on fish from exposure to NORM components in produced water was found.
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Papers by Rehan Sadiq