Horace Moo-Young

Testing procedures to assess the viability of dewatering with geotextile tubes

Abstract Geotextile tubes are finding increasing market acceptance for dewatering high water content materials. The success of this application depends on the filtration compatibility between the high water content materials and the geotextiles used to make the tubes. In this paper, 26 pressure filtration tests using four woven geotextiles of various materials were conducted to study soil retention and permeability of the sludge/geotextile system and the possible controlling factors. Based on the test results, the filter cake is not only the major contributor to the retention of fine particles, but also causes a decrease in permeability. Controlling the formation of the filter cake on the inside of the geotextiles tube and thus achieving a balance between soil retention and permeability is vital to a successful project. Surprisingly, initial water content may have a significant effect on the dewatering efficiency and dewatering rate. More testing is recommended to gain a deeper understanding into this relationship.

Evaluation of vacuum filtration testing for geotextile tubes

Abstract High water content (or low solids content) materials consist of marine sediments, industrial, wastewater, and water treatment sludges, and agricultural waste. Geotextile tubes are emerging as a new technology that can dewater high water content material. The goal of this study was to utilize vacuum filtration testing to evaluate the filtration and retention capacity of woven fabrics used for geotextile tubes and to provide design guidance in selecting appropriate geotextiles to increase solids retention while reducing excessive fines migration. A procedure for analysis of vacuum filtration test results is provided. The results of this study revealed that woven geotextiles provided adequate retention of solids. In addition, empirical equations for retention, clogging, and permeability were assessed for applicability to geotextile tube design.

Centrifuge simulation of the consolidation characteristics of capped marine sediment beds

Abstract Marine sediment capping is a technique where clean sand or sediment is placed over contaminated sediment to reduce the migration of contaminants to the environment. Environmental regulations have limited the use of in situ sediment capping due to concerns about the contaminant migration through the cap. A series of centrifuge tests were conducted to simulate the effects of consolidation settlement of capped marine sediment. This study describes the testing and monitoring of the centrifuge tests. The results from the centrifuge tests are interpreted and compared to predictions made by the PSDDF computer program, which can qualitatively estimate the consolidation settlement of capped marine sediment. Centrifuge tests were utilized to predict the consolidation of marine sediment caused by the placement of a capping layer. The centrifuge tests used the modeling of models technique to verify that correct modeling procedures were utilized. In this study, the maximum deviation between the centrifuge test results and PSDDF prediction was 20%. Thus, designers should utilize PSDDF consolidation settlement results with caution. Dye tracer studies showed the importance of consolidation-induced advective transport of contaminants. Thus, the capping layer must be appropriately designed to reduce the effects of consolidation-induced advective transport. This may be accomplished by adding a reactive barrier or geosynthetic barrier layer to the cap design.

Determination of the environmental impact of consolidation induced convective transport through capped sediment

The presence of contaminated sediment poses a barrier to essential waterway maintenance and construction in many ports and harbors, which support 95% of US foreign trade. Cost effective solutions to remediate contaminated sediments in waterways need to be applied. Capping is the least expensive remediation alternative available for marine sediments that is unsuitable for open water disposal. Dredged material capping and in situ capping alternatives, however, are not widely used because regulatory agencies are concerned about the potential for contaminant migration through the caps. Numerous studies have been conducted on the effects of diffusion through caps, however, there is a lack of experimental data documenting the effects of consolidation induced transport of contaminants through caps. This study examines consolidation induced convective contaminant transport in capped sediment utilizing a research centrifuge. In this study, consolidation induced convective transport was modeled for 7h at 100 x g, which modeled a contaminant migration time of 8 years for a prototype that was 100 times larger than the centrifuge model. In this study, hydrodynamic dispersion was a function of the seepage velocity. And, advection and dispersion dominated the migration of contaminants. Centrifuge model results were compared to an analytical solution for advection and dispersion. The advection-dispersion equation demonstrated that the centrifuge test is a conservative estimate for predicting contaminant transport. In conducting sensitivity analysis of the advection-dispersion equation to the centrifuge modeling, as hydrodynamic dispersion decreased, the time for contaminant breakthrough increased. Moreover, as the sediment to water distribution coefficient increased, the contaminant concentration into the overlying water decreased.

The migration of contaminants through geosynthetic fabric containers utilized in dredging operations

Abstract Recent changes in environmental regulations to protect the water column have prohibited the open water disposal of dredged sediment from the New York Harbor. These restrictions have decreased the average amount of dredging by the New York Port Authority by 70% for 1996. As a result, the New York Harbor will lose about a foot of depth each year if the contaminated sediments are not dredged. Decreases in the depth will have a severe economic impact, as larger cargo ships will dock in deeper ports. Because of the restrictions and perceived political problems with dredging and open water disposal of the contaminated materials, the New York Port Authority and the Corps of Engineers are investigating the use of geosynthetic fabric containers (GFCs) to reduce the movement of contaminated sediments outside the boundary of the disposal site and to decrease the impact of the sediment on the water column. During the dredging operation, the barge will be lined with the appropriate GFC to filter the dredge sediments. This laboratory study investigates the migration of fines and contaminants through GFCs. Contaminated dredges sediment was characterized for the physical and chemical properties. Bench scale filtration and barge simulation tests were conducted on the contaminated sediment and GFC configurations to determine the amount of total suspended solids that would be released to the water column.

Modeling Contaminant Transport Through Capped Dredged Sediment Using a Centrifuge

The presence of contaminated sediment poses a barrier to essential waterway maintenance and construction in many ports and harbors, which support 95% of U.S. foreign trade. Cost effective solutions to remediate contaminated sediments in waterways need to be applied. Capping is the least expensive remediation alternative available for marine sediments that is unsuitable for open water disposal. Dredged material capping and in situ capping alternatives, however, are not widely used because regulatory agencies are concerned about the potential for contaminant migration through the caps.Numerous studies have been conducted on the effects of diffusion through caps, however, there is a lack of experimental data documenting the effects of consolidation induced transport of contaminants through caps. This study examines consolidation induced advective contaminant transport in capped sediment utilizing a research centrifuge. Centrifuge modeling simulates the increase in the gravitational acceleration (g) of a prototype, which is N times larger than the model, where N is gravitational acceleration factor. For contaminant migration, the time of transport in the model is inversely proportional to the square of the acceleration factor in the prototype. In this study, consolidation induced advective transport was modeled for 22.5 hours at 100-g, which modeled a contaminant migration time of 25 years for a prototype that was 100 times larger than the centrifuge model. Thus, advection and dispersion dominated the migration of contaminants. The centrifuge modeling results were compared to an analytical solution for advection and dispersion.

Determination of the thermal conductivity of shredded tyres by utilising a hot plate apparatus

This paper presents the study of thermal conductivity of shredded tyre at varying temperature gradient. To accomplish this objective, laboratory tests have been conducted to determine the heat transfer properties of the materials that compose tyres (i.e., tyre rubber and wires) by using a hot-plate apparatus. A hot plate was adopted by the American Society for Testing and Materials (ASTM) as a standard method. In addition, one-dimensional heat conduction experiments have been conducted to compare the flow of heat through the materials while varying the physical and environmental conditions. A one-dimensional heat transfer equation was developed, and parametric studies have been conducted to verify the laboratory model. The experimental data were compared to exact solutions and Fouriers unsteady state equation. From the comparison, the respective average heat coefficient was 3.3 W/m-K; the average diffusivity was 4.6E-4 meters/hr; and the thermal conductivity was 0.30 W/m K.

Determination of the initial exothermic reaction of shredded tyres with wire content

This paper presents the cause of exothermic reactions in shredded tyre with exposed wire content in shredded tyre piles. Data indicate that the oxidation of exposed steel wires is the exothermic reaction in shredded tyre embankments. This would lead to spontaneous combustion. Reaction of the steel with the sulphur or the carbon black appears not to be the source of the exothermic. Laboratory tests have been conducted to determine the heat transfer properties of the materials that compose tyres (i.e., tyre rubber and wires) by using a hot-plate apparatus. In addition, one-dimensional heat conduction experiments were conducted to compare the flow of heat through the materials while varying the physical and environmental conditions. The physical conditions were the size of tyre shred, water content, and wire contents. An exothermic reaction occurred when exposed wire was present but not when it was absent. A one-dimensional heat transfer equation was developed, and parametric studies were conducted to verify the laboratory model. Exothermic reaction was found to increase linearly with temperature, size and shape of the shredded tyres, density, amount of wire in shredded tyres, and water content.

A Novel Treatment for Acid Mine Drainage Utilizing Reclaimed Limestone Residual

The viability of utilizing Reclaimed Limestone Residual (RLR) to remediate Acid Mine Drainage (AMD) was investigated. Physical and chemical characterization of RLR showed that it is composed of various minerals that contain significant quantities of limestone or calcium bearing compounds that can be exploited for acid neutralization. Acid Neutralization Potential (ANP) test results showed that RLR has a neutralization potential of approximately 83% as calcium carbonate (CaCO{sub 3}). Neutralization tests with most of the heavy metals associated with AMD showed removal efficiencies of over 99%. An unexpected benefit of utilizing RLR was the removal of hexavalent chromium Cr (VI) from the aqueous phase. Due to an elevation in pH by RLR most AMD heavy metals are removed from solution by precipitation as their metal hydroxides. Cr (VI) however is not removed by pH elevation and therefore subsequent ongoing tests to elucidate the mechanism responsible for this reaction were conducted.

Evaluation of Slurry Wall Construction Using Paper Clay for Containment of Contaminated Groundwater

Slurry walls have been used widely as passive vertical barriers to control the horizontal flow of groundwater and contaminants and therefore limit the migration of contaminants through the subsurface. The material used as slurry to reduce contaminant transport is expected to form a filter cake with low permeability along the sides of the trench wall/excavation face. In this article, paper mill sludge (hereafter referred to as paper clay) is investigated as a possible slurry. Previous research by Moo Young et al. (2000) has shown that paper clay has several properties that make its use in vertical barriers very promising. It can be compacted to low permeability values (10−7 cm/s to 10−9 cm/s) and has a high organic content that may act as a potential carbon source for microbial growth and sorption sites for heavy metal attenuation. To determine the feasibility of paper clay in a slurry, column testing to determine the dispersion coefficient for transport modeling, slump testing, and filter cake formation tests were performed. It is shown that the coefficient of hydrodynamic dispersion within paper clay is in the order of 10−7 cm2/ s. It is also shown that paper clay can achieve the required slump of between 5.08 and 15.24 cm (2 and 6 in) similar to that of a workable soil-bentonite backfill. Furthermore, it is shown that the filter cakes that are formed have permeability values similar to those of soil-bentonite filter cakes.