This paper presents an optimization model for solving the planning problem of collection and transportation of solid waste in medium-sized cities. As final results, are expected to promote cost savings to the public c...This paper presents an optimization model for solving the planning problem of collection and transportation of solid waste in medium-sized cities. As final results, are expected to promote cost savings to the public coffers, as well as environmental benefits. The developed mathematical model is formulated as a problem of linear programming with mixed-integer variables and transcribed into software GAMS （general algebraic modeling system）. The practical application was tested using data collected in the central region of a Brazilian city with approximately 90,000 inhabitants. The deterministic model used allowed an optimal solution. It was found after inclusion of restrictions that eliminated the appearance of sub-routes. It was concluded that the optimal routes allow for a 38% reduction in total distance traveled, which can generate savings of $320.00 per day regarding maintenance and fuel trucks.展开更多
Waste collection is an important part of waste management system.Transportation costs and carbon emissions can be greatly reduced by proper vehicle routing.Meanwhile,each vehicle can work again after achieving its cap...Waste collection is an important part of waste management system.Transportation costs and carbon emissions can be greatly reduced by proper vehicle routing.Meanwhile,each vehicle can work again after achieving its capacity limit and unloading the waste.For this,an energy-efficient multi-trip vehicle routing model is established for municipal solid waste collection,which incorporates practical factors like the limited capacity,maximum working hours,and multiple trips of each vehicle.Considering both economy and environment,fixed costs,fuel costs,and carbon emission costs are minimized together.To solve the formulated model effectively,contribution-based adaptive particle swarm optimization is proposed.Four strategies named greedy learning,multi-operator learning,exploring learning,and exploiting learning are specifically designed with their own searching priorities.By assessing the contribution of each learning strategy during the process of evolution,an appropriate one is selected and assigned to each individual adaptively to improve the searching efficiency of the algorithm.Moreover,an improved local search operator is performed on the trips with the largest number of waste sites so that both the exploiting ability and the convergence accuracy of the algorithm are improved.Performance of the proposed algorithm is tested on ten waste collection instances,which include one real-world case derived from the Green Ring Company of Jiangbei New District,Nanjing,China,and nine synthetic instances with increasing scales generated from the commonly-used capacitated vehicle routing problem benchmark datasets.Comparisons with five state-of-the-art algorithms show that the proposed algorithm can obtain a solution with a higher accuracy for the constructed model.展开更多
Wet dust removal systems used to control dust in the polishing or grinding process of Mg alloy products are frequently associated with potential hydrogen explosion caused by magnesium-water reaction.For purpose of avo...Wet dust removal systems used to control dust in the polishing or grinding process of Mg alloy products are frequently associated with potential hydrogen explosion caused by magnesium-water reaction.For purpose of avoiding hydrogen explosion risks,we try to use a combination of chitosan(CS)and sodium phosphate(SP)to inhibit the hydrogen evolution reaction between magnesium alloy waste dust and water.The hydrogen evolution curves and chemical kinetics modeling for ten different mixing ratios demonstrate that 0.4wt%CS+0.1wt%SP yields the best inhibition efficiency with hydrogen generation rate of almost zero.SEM and EDS analyses indicate that this composite inhibitor can create a uniform,smooth,tight protective film over the surface of the alloy dust particles.FTIR and XRD analysis of the chemical composition of the surface film show that this protective film contains CS and SP chemically adsorbed on the surface of ZK60 but no detectable Mg(OH)_(2),suggesting that magnesium-water reaction was totally blocked.Our new method offers a thorough solution to hydrogen explosion by inhibiting the hydrogen generation of magnesium alloy waste dust in a wet dust removal system.展开更多
The aim of this study was to assess Readiness of Healthcare facilities to Implement onsite Healthcare Waste Management Protocols and Incineration Guidelines in Tanzania. To address this, a national assessment was cond...The aim of this study was to assess Readiness of Healthcare facilities to Implement onsite Healthcare Waste Management Protocols and Incineration Guidelines in Tanzania. To address this, a national assessment was conducted country wide to assess readiness of Healthcare Facilities (HCFs) to undertake various Healthcare Waste Management (HCWM) initiatives with particular focus to adherence to HCWM protocols and incineration guidelines. The assessment of healthcare waste management was conducted in facilities in the 26 regions of Tanzania mainland for one month. A standardized checklist and tools were used to assess and monitor various aspects related to healthcare waste management using open source software for data collection (ODK). Data were analyzed using SPSS computer software. It was observed that 46.2%, 33.3% and 25% of the health centres, district hospitals and regional hospitals did not have appointed supervisors, which makes it difficult for the HCFs to perform better in managing healthcare waste in their respective facilities. It was further revealed that healthcare facilities have made remarkable improvement in the overall healthcare waste management with evidence of ongoing common activity on purchasing injection safety boxes (69.2%) and purchasing of waste bins (53.8%) at all levels. On average, about 70% of the HCFs have plans and budget though inadequate to support HCWM activities. In a conclusion Healthcare Facilities must designate a better system to compressively address healthcare waste management issues. Again the findings provide evidence for those engaged in improving HCF conditions to develop evidence-based policies and efficient programs, enhance service delivery systems, and make better use of available resources.展开更多
Waste management is one of urgent challenges in the world. In rapidly growing cities of developing countries like Accura, Ghana, waste collection is done without sufficient protection of workers. This situation became...Waste management is one of urgent challenges in the world. In rapidly growing cities of developing countries like Accura, Ghana, waste collection is done without sufficient protection of workers. This situation became worse when the COVID-19 pandemic began to threaten the health and safety of waste collection workers. This paper aims to examine waste management workers’ safety concerns during the COVID-19 pandemic in Ghana. To better understand waste management workers’ safety concerns during the pandemic, we used the questionnaire survey. Our questionnaire survey was conducted among 60 waste management workers in Accra, the capital city of Ghana. The study then discusses how municipal waste management authorities can ensure safety of waste management workers during the pandemic. Our results showed that 58% of the respondents were worried about the COVID-19 pandemic, while 20% were not even sure of the existence of the Covid-19 pandemic. Besides their worry, we also found that about 40% of the respondents had access to face masks/shields at their workplace, and 30% had hand sanitizers. This paper highlights that providing more advanced safety protocols in terms of workers daily operations and safety measures will enable a safe working environment for the workers even in terms of future pandemics.展开更多
Excessive MSW （municipal solid waste） production is a growing management problem for cities in developing countries, such as South Africa. A major problem in the city of Tshwane is that all the MSW generated in the ...Excessive MSW （municipal solid waste） production is a growing management problem for cities in developing countries, such as South Africa. A major problem in the city of Tshwane is that all the MSW generated in the city is currently being landfilled with very little recycling initiatives. Selective waste collection and sorting waste fractions out of the waste stream have become a popular survival strategy for the economically excluded population in Tshwane. Reclaimers （waste pickers） work under severe and chronic occupational health and injury risk on landfill sites. The middlemen who purchase their recovered materials exploit and marginalize them. Environmental and social awareness is however a growing issue in South Africa. The study was conducted with the aim of investigating and proposing community recycling programs and technologies to be sustainably implemented in the city of Tshwane. Successful established community recycling programs in Brazil was investigated to verify its socioeconomic and environmental impacts in a sustainable waste management perspective. Community recycling initiatives have been increasingly used as a strategy to address both the MSW problem and urban poverty in Brazil. The study focused on the city of Tshwane, but it can be argued that the findings can be implemented in any other South African municipality and in other emerging countries in Africa.展开更多
Appropriate solid waste management(SWM)strategies are necessary to avoid severe environmental and sanitary impacts,especially in low-income countries.Such strategies are most likely to succeed whether implementing act...Appropriate solid waste management(SWM)strategies are necessary to avoid severe environmental and sanitary impacts,especially in low-income countries.Such strategies are most likely to succeed whether implementing actors are supported by scientific research.In this paper,the results of a collaboration between local authorities and researchers are presented and discussed that are the assessment of waste generation in the city of Quelimane(Mozambique),integrating existing and field-collected data and the design of a small-scale center for plastic sorting to complement the SWM system of the city.The center is expected to receive about 0.3-0.4 t/day of plastic waste(5%-7%of the overall amount of plastic waste daily produced in Quelimane).As long-term sustainability represents a typical issue,simplicity of operation was a leading principle in the design of the center;moreover,the design included a treatment plant(WWTP)for generated wastewater,whose management is usually neglected in such interventions.Among others,natural wastewater treatment(constructed wetlands)has been chosen for its affordability.Noteworthy,the so-conceived WWTP appears as a novelty in the scientific literature associated with small-scale plastic sorting plants.The system is designed to treat an average flow of 6 m3/day and consisted of a septic tank followed by a subsurface flow constructed wetland.Overall,the COD(chemical oxygen demand)and TSS(total suspended solids)removal higher than 80%and 90%were estimated,respectively.Based on this work,both the center and the WWTP were successfully realized,which are waiting to become operational.In the authors’opinion,the implemented procedure could become a reference for broader investigations and surveys.展开更多
A new complex plant for carbonization and composting of municipal wastes proposed for Gero City is introduced. The separated combustible waste and non-separated combustible waste are carbonized in two fluidized carbon...A new complex plant for carbonization and composting of municipal wastes proposed for Gero City is introduced. The separated combustible waste and non-separated combustible waste are carbonized in two fluidized carbonization furnaces in the plant, and the coke produced is used in steelworks. The separated garbage and forest-wastes are mixed with dried septic-tank sludge to produce high quality compost for farms. This use of waste materials in the complex plant considerably lowers the amount of waste going to land-fills, and in addition, creates lower total emission of dioxins and carbon dioxide into the environment.展开更多
文摘This paper presents an optimization model for solving the planning problem of collection and transportation of solid waste in medium-sized cities. As final results, are expected to promote cost savings to the public coffers, as well as environmental benefits. The developed mathematical model is formulated as a problem of linear programming with mixed-integer variables and transcribed into software GAMS （general algebraic modeling system）. The practical application was tested using data collected in the central region of a Brazilian city with approximately 90,000 inhabitants. The deterministic model used allowed an optimal solution. It was found after inclusion of restrictions that eliminated the appearance of sub-routes. It was concluded that the optimal routes allow for a 38% reduction in total distance traveled, which can generate savings of $320.00 per day regarding maintenance and fuel trucks.
基金This work was supported by the Guangdong Provincial Key Laboratory(No.2020B121201001)National Natural Science Foundation of China(NSFC)(Nos.61502239 and 62002148)+1 种基金Natural Science Foundation of Jiangsu Province of China(No.BK20150924)Shenzhen Science and Technology Program(No.KQTD2016112514355531).
文摘Waste collection is an important part of waste management system.Transportation costs and carbon emissions can be greatly reduced by proper vehicle routing.Meanwhile,each vehicle can work again after achieving its capacity limit and unloading the waste.For this,an energy-efficient multi-trip vehicle routing model is established for municipal solid waste collection,which incorporates practical factors like the limited capacity,maximum working hours,and multiple trips of each vehicle.Considering both economy and environment,fixed costs,fuel costs,and carbon emission costs are minimized together.To solve the formulated model effectively,contribution-based adaptive particle swarm optimization is proposed.Four strategies named greedy learning,multi-operator learning,exploring learning,and exploiting learning are specifically designed with their own searching priorities.By assessing the contribution of each learning strategy during the process of evolution,an appropriate one is selected and assigned to each individual adaptively to improve the searching efficiency of the algorithm.Moreover,an improved local search operator is performed on the trips with the largest number of waste sites so that both the exploiting ability and the convergence accuracy of the algorithm are improved.Performance of the proposed algorithm is tested on ten waste collection instances,which include one real-world case derived from the Green Ring Company of Jiangbei New District,Nanjing,China,and nine synthetic instances with increasing scales generated from the commonly-used capacitated vehicle routing problem benchmark datasets.Comparisons with five state-of-the-art algorithms show that the proposed algorithm can obtain a solution with a higher accuracy for the constructed model.
基金This work was supported by the National Natural Science Foundation of China(52074066).
文摘Wet dust removal systems used to control dust in the polishing or grinding process of Mg alloy products are frequently associated with potential hydrogen explosion caused by magnesium-water reaction.For purpose of avoiding hydrogen explosion risks,we try to use a combination of chitosan(CS)and sodium phosphate(SP)to inhibit the hydrogen evolution reaction between magnesium alloy waste dust and water.The hydrogen evolution curves and chemical kinetics modeling for ten different mixing ratios demonstrate that 0.4wt%CS+0.1wt%SP yields the best inhibition efficiency with hydrogen generation rate of almost zero.SEM and EDS analyses indicate that this composite inhibitor can create a uniform,smooth,tight protective film over the surface of the alloy dust particles.FTIR and XRD analysis of the chemical composition of the surface film show that this protective film contains CS and SP chemically adsorbed on the surface of ZK60 but no detectable Mg(OH)_(2),suggesting that magnesium-water reaction was totally blocked.Our new method offers a thorough solution to hydrogen explosion by inhibiting the hydrogen generation of magnesium alloy waste dust in a wet dust removal system.
文摘The aim of this study was to assess Readiness of Healthcare facilities to Implement onsite Healthcare Waste Management Protocols and Incineration Guidelines in Tanzania. To address this, a national assessment was conducted country wide to assess readiness of Healthcare Facilities (HCFs) to undertake various Healthcare Waste Management (HCWM) initiatives with particular focus to adherence to HCWM protocols and incineration guidelines. The assessment of healthcare waste management was conducted in facilities in the 26 regions of Tanzania mainland for one month. A standardized checklist and tools were used to assess and monitor various aspects related to healthcare waste management using open source software for data collection (ODK). Data were analyzed using SPSS computer software. It was observed that 46.2%, 33.3% and 25% of the health centres, district hospitals and regional hospitals did not have appointed supervisors, which makes it difficult for the HCFs to perform better in managing healthcare waste in their respective facilities. It was further revealed that healthcare facilities have made remarkable improvement in the overall healthcare waste management with evidence of ongoing common activity on purchasing injection safety boxes (69.2%) and purchasing of waste bins (53.8%) at all levels. On average, about 70% of the HCFs have plans and budget though inadequate to support HCWM activities. In a conclusion Healthcare Facilities must designate a better system to compressively address healthcare waste management issues. Again the findings provide evidence for those engaged in improving HCF conditions to develop evidence-based policies and efficient programs, enhance service delivery systems, and make better use of available resources.
文摘Waste management is one of urgent challenges in the world. In rapidly growing cities of developing countries like Accura, Ghana, waste collection is done without sufficient protection of workers. This situation became worse when the COVID-19 pandemic began to threaten the health and safety of waste collection workers. This paper aims to examine waste management workers’ safety concerns during the COVID-19 pandemic in Ghana. To better understand waste management workers’ safety concerns during the pandemic, we used the questionnaire survey. Our questionnaire survey was conducted among 60 waste management workers in Accra, the capital city of Ghana. The study then discusses how municipal waste management authorities can ensure safety of waste management workers during the pandemic. Our results showed that 58% of the respondents were worried about the COVID-19 pandemic, while 20% were not even sure of the existence of the Covid-19 pandemic. Besides their worry, we also found that about 40% of the respondents had access to face masks/shields at their workplace, and 30% had hand sanitizers. This paper highlights that providing more advanced safety protocols in terms of workers daily operations and safety measures will enable a safe working environment for the workers even in terms of future pandemics.
文摘Excessive MSW （municipal solid waste） production is a growing management problem for cities in developing countries, such as South Africa. A major problem in the city of Tshwane is that all the MSW generated in the city is currently being landfilled with very little recycling initiatives. Selective waste collection and sorting waste fractions out of the waste stream have become a popular survival strategy for the economically excluded population in Tshwane. Reclaimers （waste pickers） work under severe and chronic occupational health and injury risk on landfill sites. The middlemen who purchase their recovered materials exploit and marginalize them. Environmental and social awareness is however a growing issue in South Africa. The study was conducted with the aim of investigating and proposing community recycling programs and technologies to be sustainably implemented in the city of Tshwane. Successful established community recycling programs in Brazil was investigated to verify its socioeconomic and environmental impacts in a sustainable waste management perspective. Community recycling initiatives have been increasingly used as a strategy to address both the MSW problem and urban poverty in Brazil. The study focused on the city of Tshwane, but it can be argued that the findings can be implemented in any other South African municipality and in other emerging countries in Africa.
基金This research was developed based on the project(Europe-Aid/150577/DD/ACT/MZ)funded by the European Union and implemented by the Italian Non-Governmental Organization Celim(Centro Laici Italiani per le Missioni)in partnership with local authorities.
文摘Appropriate solid waste management(SWM)strategies are necessary to avoid severe environmental and sanitary impacts,especially in low-income countries.Such strategies are most likely to succeed whether implementing actors are supported by scientific research.In this paper,the results of a collaboration between local authorities and researchers are presented and discussed that are the assessment of waste generation in the city of Quelimane(Mozambique),integrating existing and field-collected data and the design of a small-scale center for plastic sorting to complement the SWM system of the city.The center is expected to receive about 0.3-0.4 t/day of plastic waste(5%-7%of the overall amount of plastic waste daily produced in Quelimane).As long-term sustainability represents a typical issue,simplicity of operation was a leading principle in the design of the center;moreover,the design included a treatment plant(WWTP)for generated wastewater,whose management is usually neglected in such interventions.Among others,natural wastewater treatment(constructed wetlands)has been chosen for its affordability.Noteworthy,the so-conceived WWTP appears as a novelty in the scientific literature associated with small-scale plastic sorting plants.The system is designed to treat an average flow of 6 m3/day and consisted of a septic tank followed by a subsurface flow constructed wetland.Overall,the COD(chemical oxygen demand)and TSS(total suspended solids)removal higher than 80%and 90%were estimated,respectively.Based on this work,both the center and the WWTP were successfully realized,which are waiting to become operational.In the authors’opinion,the implemented procedure could become a reference for broader investigations and surveys.
文摘A new complex plant for carbonization and composting of municipal wastes proposed for Gero City is introduced. The separated combustible waste and non-separated combustible waste are carbonized in two fluidized carbonization furnaces in the plant, and the coke produced is used in steelworks. The separated garbage and forest-wastes are mixed with dried septic-tank sludge to produce high quality compost for farms. This use of waste materials in the complex plant considerably lowers the amount of waste going to land-fills, and in addition, creates lower total emission of dioxins and carbon dioxide into the environment.
