Masashi Kamon

MSW fly ash stabilized with coal ash for geotechnical application

The solidification and stabilization of municipal solid waste (MSW) fly ash for the purpose of minimizing the geo-environmental impact caused by toxic heavy metals as well as ensuring engineering safety (strength and soaking durability) are experimentally evaluated. The mixtures of MSW fly ash stabilized with cement and fluidized bed combustion coal fly ash (FCA) were used for unconfined compressive strength tests, leachate tests, and soaking tests. The behavior of soluble salts contained in the MSW fly ash significantly affects strength development, soaking durability, and the hardening reaction of the stabilized MSW fly ash mixtures. The cement stabilization of the MSW fly ash does not have enough effect on strength development and soaking durability. The addition of cement only contributes to the containment of heavy metals due to the high level of alkalinity. When using FCA as a stabilizing agent for MSW fly ash, the mixture exhibits high strength and durability. However, the Cd leachate cannot be prevented in the early stages of curing. Using a combination of cement and FCA as a MSW fly ash stabilizer can attain high strength, high soaking durability, and the containment of heavy metals. The stabilized MSW fly ash with cement and FCA can be practically applied to embankments.

Measuring the k-S-p relations on DNAPLs migration

Abstract Migration characteristics of dense non-aqueous phase liquids (DNAPLs) in the subsurface can be expressed as a water–DNAPL two-phase system based on mainly the k – S – p relations, which describe the relations among relative permeability ( k ), degree of water saturation ( S ), and capillary pressure head ( p ). The aims of this research are to develop an experimental system with new type of probes, such as the electrical conductivity probe for measuring the degree of water saturation and the hydrophilic and hydrophobic tensiometer for measuring the pore water and DNAPL pressures, and also to estimate the results obtained from the developed experimental system. From these tests, the excellent k – S – p relations were obtained and the efficiency and validity of this developed experimental system have been confirmed in terms of the concept of the scaling coefficient calculated by interfacial tensions.

Column test-based optimization of the permeable reactive barrier (PRB) technique for remediating groundwater contaminated by landfill leachates.

We investigated the optimum composition of permeable reactive barrier (PRB) materials for remediating groundwater heavily contaminated by landfill leachate, in column tests using various mixtures of zero-valent iron (ZVI), zeolite (Zeo) and activated carbon (AC) with 0.01-0.25, 3.0-5.0 and 0.7-1.0mm grain sizes, respectively. The main contributors to the removal of organic/inorganic contaminants were ZVI and AC, and the optimum weight ratio of the three PRB materials for removing the contaminants and maintaining adequate hydraulic conductivity was found to be 5:1:4. Average reductions in chemical oxygen demand (COD) and contents of total nitrogen (TN), ammonium, Ni, Pb and 16 polycyclic aromatic hydrocarbons (PAHs) from test samples using this mixture were 55.8%, 70.8%, 89.2%, 70.7%, 92.7% and 94.2%, respectively. We also developed a systematic method for estimating the minimum required thickness and longevity of the PRB materials. A ≥ 309.6 cm layer with the optimum composition is needed for satisfactory longevity, defined here as meeting the Grade III criteria (the Chinese National Bureau of Standards: GB/T14848/93) for in situ treatment of the sampled groundwater for ≥ 10 years.

Hydraulic Barrier Performance of SBM Cut-off Wall constructed by the Trench Cutting and Re-mixing Deep Wall Method

Containment using a soil-bentonite mixture (SBM) cut-off wall is a valid method to prevent the contaminants in soil from migrating in the aquifer. A new construction technique for the SBM vertical cut-off wall has been developed by employing the trench cutting and re-mixing deep wall method to achieve excellent homogeneity of the wall. This paper addresses this construction method and the laboratory testing results on the hydraulic barrier performance of SBM focusing on its chemical compatibility. Hydraulic conductivity values were measured for SBM specimens, which were processed from various types of soil with different concentrations of divalent cation (Ca 2+ ) in the permeant or in the pore water of original soil. For the Ca 2+ concentrations lower than 0.01 M in soil pore water, there is no significant effect on the hydraulic conductivity of SBM. For the higher Ca 2+ concentrations, more than one order of magnitude higher hydraulic conductivity values were observed. The correlation between the hydraulic conductivity and the void ratio change in SBM specimen implies that the void ratio change could be a good indicator of the hydraulic conductivity for different types of soil.

Biochemical Effects on the Long-Term Mobility of Heavy Metals in Marine Clay at Coastal Landfill Sites

In coastal landfill facilities that are constructed to contain municipal and industrial wastes in Japan, natural marine clay layers serve as bottom liners to prevent pollutant migration. Leachates from landfills are rich in dissolved organic carbon (DOC) that can be used by micro-organisms. Biological processes could lead to redox reactions that change the pH and Eh. These biochemical factors may strongly influence the behavior of pollutants leached from landfills, particularly heavy metals. In this paper, modified batch tests were conducted to investigate the effects of pH and Eh and to simulate both chemical and biochemical reactions on zinc mobility in a marine clay layer. To examine the effects of pH and Eh, the pH and Eh were controlled by adding acid or base, respectively, and a reducing agent. To study the zinc mobility, biochemical reactions were enhanced by cultivating native micro-organisms, which gradually changed the pH and Eh conditions. Batch tests with different DOC concentrations were also conducted to evaluate the effect of DOC on zinc mobility. In addition, biochemical processes in the bottom clay liners at coastal landfill sites that receive municipal solid waste (MSW) incinerator ash were simulated by batch tests using a solution of MSW incinerator ash mixed with seawater along with cultivating native micro-organisms found in marine clay. The experimental results indicated that microbial activities in closed soil-water systems result in strongly reduced conditions compared to that controlled by a strong reducing agent, and that the zinc mobility is lowered through the formation of sulfides. Although microbial activity was initially limited under highly alkaline conditions due to MSW incinerator ash, the pH gradually decreased mainly due to the formation of organic acids from microbial activity. Under the oxidized conditions, the solubility of zinc was controlled by pH and the Eh had a negligible effect on the zinc concentration. DOC in the leachate served as a bioavailable carbon source for microbial activities, which promoted anaerobic conditions in the soil-water system and the immobilization of zinc. However, DOC also formed soluble complexes with heavy metals, which increased the zinc concentration. These observations confirmed that heavy metals in the leachates became immobilized under the conditions found at landfill bottom liners when estimated in terms of pH, Eh, and DOC.

Gas Permeability of Hybrid Geosynthetics for Landfill Cap Cover

Landfill cap covers that suppress water infiltration to the waste and promote rapidly gas permeation at the same time are demanded. We have developed hybrid geosynthetics that consist of porous sheet and nonwoven geotextiles as landfill cap covers and their basic performances have been investigated by laboratory and field tests. In this study, gas permeability of porous sheets was evaluated by laboratory test. Field test was also conducted to examine gas permeability of the hybrid geosynthetics installed in the underground. In both tests, variation of substitution rate of nitrogen gas with time at both spaces divided by the sample was investigated, while nitrogen gas was introduced to one side of the spaces. As the results, it was clarified that porous sheets themselves are suggested to have sufficient fundamental characteristics on permeability of gases with chemically-inactive and sufficiently small in molecular size. It was also demonstrated that hybrid geosynthetics exhibits gas permeability even when installed in the underground.

Speciation and mobility assessment of zinc in coastal landfill sites with MSW incinerator ash.

The mobility of zinc in coastal landfill sites reclaimed by municipal solid waste incinerator ash (MSWIA) was modeled and investigated by conducting a large column test. Temporal and spatial variations in the pH, redox potential (Eh), total organic carbon, and microbial activity were measured in pore water to observe their influences on the mobility of heavy metals throughout the test. After 502 days, permeation was terminated. Then to determine the content and forms of Zn along the column, MSWIA and marine clay samples were analyzed by the community bureau of reference modified sequential extraction procedure. Zn was partitioned into four defined chemical fractions: exchangeable, reducible, oxidizable, and residual. The results showed that attenuation processes occurred within the ash layer, Zn mobility was minor, and coastal landfill conditions promoted the immobilization of heavy metals. Both pH and Eh were the main factors for controlling the solubility of Zn. Moreover, under reduced-alkaline conditions, the reducible fraction was affected, but the oxidizable fraction was slightly favored. The formation of zinc sulphides might be another attenuation mechanism for Zn.

Large-Scale Shear Tests on Interface Shear Performance of Landfill Liner Systems

Interface shear performance of various landfill liner systems were evaluated for landfill stability by conducting large scale shear tests. Testing program covers the interfaces between (1) geosynthetics (geomembrane (GM) sheet (HDPE and PVC) and non-woven geotextile) and subsoil, (2) geosynthetics and compacted clay liner (CCL), and (3) GM and geotextile. The focus of this paper is placed on interface shear performance under both as installed condition (dry for geosynthetics and optimum moisture content for CCL or subsoil) and saturated / wet condition, since landfill liner system is often subjected to saturated / wet condition due to the higher water retention capacity of CCL as well as the contact to leachate and/or groundwater. For geotextile-GM interface, there is no significant effect on the interface shear strength. The saturated CCL-GM interface had lower shear strength compared to the interface under as installed condition, although the shear performances of CCL-geotextile interface under both conditions are similar to each other. For the interfaces between geosynthetics and subsoil, the frictional resistance of HDPE with textures surface had a significant drop from 23 to 15 degree in the saturated / wet condition.

Speciation and Mobility Assessment of Heavy Metals in the Coastal Municipal Solid Waste Incinerator Ash Landfill

In the metropolitan areas of Japan, coastal landfills have become a practical and main solution for the disposal of municipal solid waste incinerator ash (MSWIA) due to limited inland space. Leachate from the landfilled MSWIA contains many dissolved and suspended substances harmful to the surrounding environment, particularly heavy metals, such as lead, zinc, and cadmium. The mobility assessment of these heavy metals is therefore one of the important environmental issues for the coastal landfill. In this paper, modified batch tests were conducted to investigate the effects of pH and Eh changes on the mobility of heavy metals in both MSWIA and marine clay layer. Based on the speciation of heavy metals by using a sequential extraction method in the leachate-MSWIA and leachate-marine clay systems, heavy metal mobility and availability were discussed with the comparison to large-scale model test results presented by (Kamon et al. “Biochemical Effects on the Long-Term Mobility of Heavy Metals in Marine Clay at Coastal Landfill Sites,” J. ASTM Int., Vol. 3, 2006), which provides the long-term change in heavy metal concentrations and forms in the coastal MSWIA landfill site. Under the high pH (≈11) and low Eh (≈−200 mV) condition in the MSWIA-leachate system, Zn, Pb, and Cd were effectively immobilized by the formation of the reducible and oxidizable fractions of Zn and the oxidizable and residual (insoluble) fractions of Pb significantly. However, the potential mobility of Cd was relatively high since the formation of exchangeable compounds was more dominantly contributed to the immobilization. Test results on the speciation of the metals in the marine clay-leachate system accounts well for the evidence that the marine clay acts as the attenuation layer for heavy metals in leachate. These findings strongly support that heavy metal mobility is restricted in the coastal MSWIA landfill due to the formation of stable and insoluble forms under reduced-alkaline condition and the attenuation effect of the marine clay.

Electrokinetic Dewatering and Sedimentation of Dredged Contaminated Sediment

This research focuses on electrokinetic dewatering and settling of contaminated sediment. A series of laboratory experiments with different magnitudes of applied voltage is performed with artificially made contaminated sediment mixed with contaminant. Investigated parameters in experiments are settlements of the slurry specimen, volumes of water extracted from the slurry specimen, and the changes in fluid content of the specimen. The results show that the sedimentation rate and velocity are varied and controlled by the applied voltage. From the test results, a significant investigation is derived for the mechanisms associated with dewatering and sedimentation of contaminated sediment. A coupled effect of electrokinetic dewatering and settling processes is investigated.