While soil vapor extraction has been widely utilized as a remedial action technology over the past decade, design and associated process performance modeling of full-scale systems continues to be frequently based on the results of pilot-scale treatability tests. To aid engineers in conducting preliminary scoping studies without the benefit of such treatability data, a relatively simple approach, consisting of linked design and process performance elements, was developed and subsequently incorporated into a spreadsheet format for rapid project evaluation purposes. Under this approach, a preliminary design is specified via a set of baseline values which vary based on the predominant soil type encountered at a particular site. Process performance is then mathematically modeled by a semi-empirical relation accounting for non-equilibrium (mass transfer) effects via use of a lumped parameter, the venting efficiency factor (η). Values for η vary based on characterization of soil heterogeneity. The low values cited for η (on the order of 0.02–0.20) reflect the relative inefficiency of field venting operations (due to inherent mass transfer limitations) when compared to idealized conditions. Validation results, considering two case studies reported in the literature, indicate that the approach developed provides reasonably accurate predictions. Evaluation of a hypothetical case study reveals that the number of extraction vents required as well as the number of pore volumes of soil vapor that must be extracted for effective remediation can vary by an order of magnitude depending upon the particular soil matrix encountered.
{"title":"A simplified approach for preliminary design and process performance modeling of soil vapor extraction systems","authors":"J. Staudinger, P. Roberts, James D. Hartley","doi":"10.1002/EP.3300160319","DOIUrl":"https://doi.org/10.1002/EP.3300160319","url":null,"abstract":"While soil vapor extraction has been widely utilized as a remedial action technology over the past decade, design and associated process performance modeling of full-scale systems continues to be frequently based on the results of pilot-scale treatability tests. To aid engineers in conducting preliminary scoping studies without the benefit of such treatability data, a relatively simple approach, consisting of linked design and process performance elements, was developed and subsequently incorporated into a spreadsheet format for rapid project evaluation purposes. Under this approach, a preliminary design is specified via a set of baseline values which vary based on the predominant soil type encountered at a particular site. Process performance is then mathematically modeled by a semi-empirical relation accounting for non-equilibrium (mass transfer) effects via use of a lumped parameter, the venting efficiency factor (η). Values for η vary based on characterization of soil heterogeneity. The low values cited for η (on the order of 0.02–0.20) reflect the relative inefficiency of field venting operations (due to inherent mass transfer limitations) when compared to idealized conditions. Validation results, considering two case studies reported in the literature, indicate that the approach developed provides reasonably accurate predictions. Evaluation of a hypothetical case study reveals that the number of extraction vents required as well as the number of pore volumes of soil vapor that must be extracted for effective remediation can vary by an order of magnitude depending upon the particular soil matrix encountered.","PeriodicalId":11769,"journal":{"name":"Environmental Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73763221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The US military has historically conducted activities which have either directly or indirectly contributed to environmental contamination. Metal contaminated soil at military sites has resulted from operations such as weapons production, small arms training activities, metal cleaning, and metal plating activities. Soil washing is an effective approach to the treatment of contaminated soils employing both physical and chemical separation techniques. Physical separation methods encompass many different unit operations including screening, grinding, flotation, hydroclassification, attrition scrubbing and gravity concentration such as tabling and spiraling. The primary focus of this paper will be to address the effects of attrition scrubbing (an abrasive soil particle to soil particle interaction in a high solids environment), on a gravity concentration process. Soil from an Army small arms training range with lead contamination in the bulk soil at approximately 40,000 mg/kg, was evaluated using a WEMCO® Laboratory Attrition Scrubber in conjunction with a Wilfley® Laboratory Wet Shaking Table. Results indicate attrition scrubbing enhanced the physical separation process on the wet shaker table by liberating the Pb contamination from the bulk soil, which resulted in a large volume of clean soil while simultaneously producing a small volume of Pb concentrated soil. Laboratory tests indicate over 96% of the contamination could be concentrated on 20% of the original soil mass.
{"title":"Heavy metal soil remediation: The effects of attrition scrubbing on a wet gravity concentration process","authors":"M. A. Marino, R. M. Brica, C. Neale","doi":"10.1002/EP.3300160318","DOIUrl":"https://doi.org/10.1002/EP.3300160318","url":null,"abstract":"The US military has historically conducted activities which have either directly or indirectly contributed to environmental contamination. Metal contaminated soil at military sites has resulted from operations such as weapons production, small arms training activities, metal cleaning, and metal plating activities. \u0000 \u0000Soil washing is an effective approach to the treatment of contaminated soils employing both physical and chemical separation techniques. Physical separation methods encompass many different unit operations including screening, grinding, flotation, hydroclassification, attrition scrubbing and gravity concentration such as tabling and spiraling. The primary focus of this paper will be to address the effects of attrition scrubbing (an abrasive soil particle to soil particle interaction in a high solids environment), on a gravity concentration process. \u0000 \u0000Soil from an Army small arms training range with lead contamination in the bulk soil at approximately 40,000 mg/kg, was evaluated using a WEMCO® Laboratory Attrition Scrubber in conjunction with a Wilfley® Laboratory Wet Shaking Table. Results indicate attrition scrubbing enhanced the physical separation process on the wet shaker table by liberating the Pb contamination from the bulk soil, which resulted in a large volume of clean soil while simultaneously producing a small volume of Pb concentrated soil. Laboratory tests indicate over 96% of the contamination could be concentrated on 20% of the original soil mass.","PeriodicalId":11769,"journal":{"name":"Environmental Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87924563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Many wastewater treatment plants, over the years, have been designed and constructed with little thought being given to details that allow the whole to work as a system, and often provides little ease of operation and maintenance. Based on over 35 years experience in the field, the following are some observations of often overlooked details which a design engineer should consider. This will be categorized into the following: Front End Design, Treatability Studies, Primary Treatment, Biological Treatment, Secondary Clarification, VOC Control, Solids Dewatering and Disposal, Recycle/Reuse, and Spent Caustic Treatment.
{"title":"Important design considerations in wastewater treatment plants","authors":"Don Vacker","doi":"10.1002/EP.3300160314","DOIUrl":"https://doi.org/10.1002/EP.3300160314","url":null,"abstract":"Many wastewater treatment plants, over the years, have been designed and constructed with little thought being given to details that allow the whole to work as a system, and often provides little ease of operation and maintenance. Based on over 35 years experience in the field, the following are some observations of often overlooked details which a design engineer should consider. This will be categorized into the following: Front End Design, Treatability Studies, Primary Treatment, Biological Treatment, Secondary Clarification, VOC Control, Solids Dewatering and Disposal, Recycle/Reuse, and Spent Caustic Treatment.","PeriodicalId":11769,"journal":{"name":"Environmental Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81034944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Studies of polychlorinated biphenyl (PCB) desorption from soils have been conducted in a laboratory scale supercritical fluid extraction (SFE) unit to provide information for soil remediation. The results demonstrate the effectiveness of SFE as a promising technology for the clean up of PCB contaminated soils/sediments. After 30 minutes of extraction at 40°C and 100 atm, more than 86% ofPCBs in real world Hudson River sediment and 92% in St. Lawrence River sediment were removed. The extraction of PCBs from spiked samples showed even higher efficiencies. Various effects such as temperature, pressure, cosolvent, sample water content, and soil/sediment type on PCB desorption have been investigated. The sample water content and the presence of co-solvent were shown to be the most important factors affecting desorption of PCBs. The results show that PCBs in real world samples are more tightly bound than in spiked samples. The desorption behavior of individual PCB congeners in various samples has been investigated. The results demonstrate no relative accumulation of the most environmentally threatening PCB congeners throughout the extraction process.
{"title":"Remediation of polychlorinated biphenyl contaminated soils/sediments by supercritical fluid extraction","authors":"P. Chen, W. Zhou, L. Tavlarides","doi":"10.1002/EP.3300160320","DOIUrl":"https://doi.org/10.1002/EP.3300160320","url":null,"abstract":"Studies of polychlorinated biphenyl (PCB) desorption from soils have been conducted in a laboratory scale supercritical fluid extraction (SFE) unit to provide information for soil remediation. The results demonstrate the effectiveness of SFE as a promising technology for the clean up of PCB contaminated soils/sediments. After 30 minutes of extraction at 40°C and 100 atm, more than 86% ofPCBs in real world Hudson River sediment and 92% in St. Lawrence River sediment were removed. The extraction of PCBs from spiked samples showed even higher efficiencies. Various effects such as temperature, pressure, cosolvent, sample water content, and soil/sediment type on PCB desorption have been investigated. The sample water content and the presence of co-solvent were shown to be the most important factors affecting desorption of PCBs. The results show that PCBs in real world samples are more tightly bound than in spiked samples. The desorption behavior of individual PCB congeners in various samples has been investigated. The results demonstrate no relative accumulation of the most environmentally threatening PCB congeners throughout the extraction process.","PeriodicalId":11769,"journal":{"name":"Environmental Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75179384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A multitude of processes have been proposed for removal of hydrogen sulfide from gaseous streams. Removal of H 2 S from sour natural gas streams is particularly difficult since low outlet concentrations must be reached before the gas is put into a pipeline. Liquid redox sulfur recovery (LRSR) processes use a solution containing an oxidizing agent that absorbs H 2 S from the gas stream and oxidizes it to sulfur. The chemistry of these processes has undergone considerable evolution in the last 30 years. A number of tradeoffs must be considered in designing LRSR processes. For example, the rate of reaction of the oxidized agent with H 2 S often determines the scrubbing efficiency, but excessive rates of sulfur formation in the scrubber can lead to plugging. Systems based on vanadium and/or anthraquinone disulfonates (ADA) as the redox catalyst had several drawbacks, most of which can be traced to sluggish redox agent kinetics. Current LRSR processes use chelated iron as the catalyst for sulfur recovery. This gives faster scrubbing and re-oxidation kinetics, but chemical degradation of the chelating agent can affect the economics of the process. Plugging of sorption vessels continues to be a problem in some applications. New nonaqueous solvent-based or biological processes may overcome these problems.
{"title":"Chemical evolution of liquid redox processes","authors":"D. Deberry","doi":"10.1002/EP.3300160316","DOIUrl":"https://doi.org/10.1002/EP.3300160316","url":null,"abstract":"A multitude of processes have been proposed for removal of hydrogen sulfide from gaseous streams. Removal of H 2 S from sour natural gas streams is particularly difficult since low outlet concentrations must be reached before the gas is put into a pipeline. Liquid redox sulfur recovery (LRSR) processes use a solution containing an oxidizing agent that absorbs H 2 S from the gas stream and oxidizes it to sulfur. The chemistry of these processes has undergone considerable evolution in the last 30 years. A number of tradeoffs must be considered in designing LRSR processes. For example, the rate of reaction of the oxidized agent with H 2 S often determines the scrubbing efficiency, but excessive rates of sulfur formation in the scrubber can lead to plugging. Systems based on vanadium and/or anthraquinone disulfonates (ADA) as the redox catalyst had several drawbacks, most of which can be traced to sluggish redox agent kinetics. Current LRSR processes use chelated iron as the catalyst for sulfur recovery. This gives faster scrubbing and re-oxidation kinetics, but chemical degradation of the chelating agent can affect the economics of the process. Plugging of sorption vessels continues to be a problem in some applications. New nonaqueous solvent-based or biological processes may overcome these problems.","PeriodicalId":11769,"journal":{"name":"Environmental Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77242955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Suda, M. Iijima, H. Tanaka, S. Mitsuoka, Toru Iwaki
The countercurrent absorption of CO 2 from the flue gas into aqueous alkanolamines has been studied using wetted wall column equipment connected to the stack of a power plant. The absorption rates of CO 2 into aqueous alkanolamines (primary amine (monoethanolamine), hindered amine (2-amino-2-methyl-1-propanol), diol secondary amine (diethanolamine), secondary amine (2-(methylamino)ethanol, 2-(ethylamino)ethanol, 2-(butylamino)ethanol), tertiary amine (2-(diethylamino)ethanol, 4-dimethylamino-1-butanol), diamine (2-(2-aminoethylamino)ethanol)) were measured at 40°C, 10kPa partial pressure, and 2m 3 /h of gas flow rate. From the rate of absorption and the absorption equilibrium results, the secondary amines have as large overall mass transfer coefficients as monoethanolamine. However, the coefficients of the hindered and tertiary amines are small even though the absorbed amounts of CO 2 at equilibrium are large. The CO 2 concentration profiles in a wetted wall column were estimated, and these results are due to the absorption process in connection with the degree of carbamate formation.
{"title":"Countercurrent absorption of CO2 in a real flue gas into aqueous alkanolamine solutions in a wetted wall column","authors":"T. Suda, M. Iijima, H. Tanaka, S. Mitsuoka, Toru Iwaki","doi":"10.1002/EP.3300160317","DOIUrl":"https://doi.org/10.1002/EP.3300160317","url":null,"abstract":"The countercurrent absorption of CO 2 from the flue gas into aqueous alkanolamines has been studied using wetted wall column equipment connected to the stack of a power plant. The absorption rates of CO 2 into aqueous alkanolamines (primary amine (monoethanolamine), hindered amine (2-amino-2-methyl-1-propanol), diol secondary amine (diethanolamine), secondary amine (2-(methylamino)ethanol, 2-(ethylamino)ethanol, 2-(butylamino)ethanol), tertiary amine (2-(diethylamino)ethanol, 4-dimethylamino-1-butanol), diamine (2-(2-aminoethylamino)ethanol)) were measured at 40°C, 10kPa partial pressure, and 2m 3 /h of gas flow rate. From the rate of absorption and the absorption equilibrium results, the secondary amines have as large overall mass transfer coefficients as monoethanolamine. However, the coefficients of the hindered and tertiary amines are small even though the absorbed amounts of CO 2 at equilibrium are large. The CO 2 concentration profiles in a wetted wall column were estimated, and these results are due to the absorption process in connection with the degree of carbamate formation.","PeriodicalId":11769,"journal":{"name":"Environmental Progress","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76360918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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