Thesis advisor: Rudolph Hon / In the northeast United States, arsenic (As) contamination in groundwater is frequently associated with historical landfill leachate plumes. Based on the history of Shepley's Hill Landfill (SHL) in Devens, MA, solid waste disposal activities spanned nearly a century of landfilling with little or no documentation of when or what waste material was disposed. Past geochemical investigations proved the presence of high levels of As in groundwaters within and around the SHL region. A total of 114 samples were collected from the SHL region and analyzed for their hydrogeochemistry and isotopic signature. Since the isotopic ratios of äD and ä18O can potentially be influenced by the mobilization process of As, this study attempts to identify any correlations between the stable isotopic ratios and the hydrogeochemistry of SHL waters. The results of the groundwater hydrogeochemical analysis show multiple relationships between metal concentrations and As concentration levels, typical of groundwater undergoing redox reactions. The result of the stable isotope analysis show significant fractionation of stable isotope ratios away from the meteoric water line. However, the role of strong redox gradients and various redox ladder reactions involving water did not produce a significant correlation with the isotopic fractionations present within different zones of the landfill. In most cases, the fractionations stand independent of the increase/decrease in As concentration and can be attributed to either unrelated chemical reactions within groundwater or evaporation. / Thesis (MS) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Due to the pressure of recent legislative changes (eg: the EU Landfill Directive and the imposition of a Landfill Tax), composting as a waste disposal technique is now being viewed as the preferred alternative to the landfilling of organic waste. However, while composting has been practised in one form or another for 2500 years, the underlying principles behind the microbial ecology of composting, is poorly understood. In order to obtain an insight into the ecology and hence, the critical nature of the composting process, a number of low cost open-windrows containing urban botanical wastes were established. These windrows were subjected to microbial and physico-chemical analysis over the initial period of exothermically active composting (25 days). This study demonstrated that, whilst average temperatures within open windrows can reach in excess of 65 °C, the sustainability and range of these temperatures depended upon the windrow bulk density. Windrows with bulk densities of 600kgm*3 had a larger insulation factor and thus, were able to sustain high temperatures for longer periods. However, these windrows were more susceptible to the development of areas of low temperature (cold spots) at depths below 20cm. Windrows with bulk densities of 400kgm'3 had smaller insulation factors and therefore, lost heat at a faster rate than windrows with higher bulk densities. This loss of heat was observed to be the case with the windrow surface layers, but they exhibited fewer cool spots at lower levels. This study found that the average microbial population of windrow material was 2.29x1013 CFU kg*1 and that each microbial cell could generate between 6.33 and 8.56xl0*13 Mjkg*1. This resulted in the generation of between 1.13 and 1.70 Mjkg*1 °C*1 of heat energy. Contrary to the published literature, this study observed that temperatures above 65 °C did not result in the significant loss of ammonia from the windrow. However, high levels of ammonia did suppress the formation of nitrate within the windrows. Experiments investigating microbial population kinetics within the windrows indicated that observed changes were proportional to temperature up to 60 °C, when a reduction in population numbers was observed between 60 °C and 65 °C. However, between 60 °C and 70 °C population levels increased once again. It was also noted that at the start of the composting process, 13 different microbial species or genera could be identified. However, after 17 days of exothermic composting, this had been reduced to 2 genera, including a novel large bacterial species belonging to the genus Bacillus. This study also showed that samples of windrows exposed to temperatures above 55 °C for 48 hours did not eliminate mesophilic or psycrotrophic microbial populations as previously assumed by other workers, but only suppressed their metabolism during the high temperature period.

Research Doctorate - Doctor of Philosophy (PhD) / Consolidation of clayey contaminant barriers, such as are employed as landfill liners, has been postulated as a cause of accelerated transit of contaminants and hence their earlier than expected appearance in secondary leachate. This proposition is theoretically investigated in this thesis using a novel large-deformation, one-dimensional continuum model of coupled mechanical consolidation and solute transport. The model is a generalization of existing coupled consolidation and solute transport models described in the literature. It takes into account both non-linearities in geometry as well as material constitutive relations. The latter relate the compressibility, hydraulic conductivity and effective diffusion coefficient to the deformation of the soil. In addition to providing details of the governing equations and constitutive relations, a detailed derivation of the three classical one-dimensional consolidation boundary conditions, i.e. undrained top and drained bottom, drained top and undrained bottom, drained top and bottom is also given. From the continuum model formulation, a numerical model was developed using proprietary finite element software – FEMLAB 2.3. The numerical model is verified by comparing results with those produced from other recently developed consolidation – transport models. In the course of conducting these comparisons, some results from a recent modelling investigation indicating that a twenty-fold reduction in the transit time of contaminants across a composite soil – geomembrane barrier may be possible were re-examined. This comparison reveals some apparent errors in the original analysis and indicates that the predicted large acceleration of contaminant transport induced by consolidation is probably unrealistic. The model is subsequently applied to a case study of a clay liner and geomembrane system. Results obtained are compared with those from various simplified models, including a “diffusion-only” (i.e. a rigid soil) model traditionally used in contaminant barrier design. For barriers incorporating low compressibility soils (such as well compacted clays), there is little difference between contaminant transit times predicted by the two models. However, for contaminant barriers incorporating more compressible soils, consolidation is shown to be capable of accelerating transport. These results indicate the potential importance of accounting for the effects of soil consolidation and they highlight some limitations of existing models when modelling solute transport through composite barriers utilizing soft soils. Based on these limited results, a way of taking into account soil consolidation using simplified models is suggested. In the penultimate chapter of this thesis, an extensive parametric sensitivity analysis of coupled consolidation and solute transport in composite contaminant barrier systems is presented. The analysis incorporates results of more than 3000 simulations for various combinations of barrier thickness, waste loading rate, initial void ratio, compression index, hydraulic conductivity and dispersion coefficient. Results are succinctly presented using dimensionless plots, which allow the comparison of results for a large number of parameter values, and hence, the clear identification of the most important factors affecting contaminant transport through a consolidating composite barrier system. The results demonstrate that there exists a pessimum rate of consolidation for which the contaminant transit time is minimised. In cases of extremely high barrier compressibility it is shown that an order of magnitude reduction in contaminant transit time may arise due to coupling between solute transport and consolidation. For barriers of low compressibility and porosity, such as well-engineered composite compacted clay landfill liners, it is found that the contaminant transit time is far less affected, though it may still be reduced by up to 30%. In general, the results suggest that the use of a coupled consolidation–contaminant transport model may be required for informed and conservative contamiant barrier design, especially if relatively compressible earthen components are utilised.

Thesis (M.Sc.)--University of Hong Kong, 1998. / Includes bibliographical references (leaf 71-73) Also available in print.

It is estimated that 22 000 contaminated areas exist in Sweden today. In order to classify the risk of contaminant migration from these areas and to prioritize which of these contaminated areas should first be treated, the Swedish Environmental Protection Agency (EPA) has designed a method, for the investigation of contaminated areas (MIFO). One of these contaminated areas is the landfill Gräsötippen outside Köping. The landfill has been used by both Yara AB and the Köping municipality between the years 1945 and 1975, and both industrial and household waste have been deposited there. The aim of this report is to survey which contaminants that can be found in the soil and water in the landfill Gräsötippen and to evaluate the migration of these contaminants. With help of this information, the landfill will then be risk classified according to MIFO. The goal is that this report will provide a basis for future studies and remedial measures at the landfill. To get a picture of what has been deposited at the landfill Gräsötippen, employees and former employees at Yara and others with connection to the landfill have been interviewed. Piezometers have been installed in and around the landfill so as to provide information on groundwater levels and movement, and for the collection of groundwater samples. Soils samples were collected as well. The water and soil samples were analyzed with regard to metals, organic compounds and nutrients. Furthermore, groundwater flow has been modeled using VS2DI, in order to get a picture of the groundwater’s flow direction and velocity under the landfill. In the water samples, only lead was detected with levels over the Maximum Contaminant Level (MCL) from the EPA. Relatively high levels of nutrients were also detected. In the soil, carcinogenic PAH, PCB, aliphatic hydrocarbons, aromatic hydrocarbons, arsenic, lead, cadmium, mercury and zinc were detected over the EPA MCL. The landfill Gräsötippen has a good location in an area with deep clay, which prevents rapid spreading of contaminants. No high levels of contaminants are leaching out today. The spreading of the contaminants is minor; most of the contaminants are fixed in the soil and do not spread to the surroundings. The water flow’s primary direction from the landfill is south but there are also flows to the west and east. Today, there are a number of proposals with regard to decreasing the risk for future contaminant dispersal from the landfill and to keep control of the water that is used in the area. A few of these proposals are to finally cover the landfill, to analyze the grass and plants in the enclosed pasture on the landfill, and to continuously analyze the water in the installed piezometers and drinking water wells on and around the landfill. The landfill Gräsötippen is classified to risk class 3, moderate risk, according to MIFO. / Det uppskattas idag finnas 22 000 förorenade områden i Sverige. För att kunna riskklassa dessa förorenade områden och prioritera vilka som först bör efterbehandlas har Naturvårdsverket utarbetat en Metodik för Inventering av Förorenade Områden (MIFO). Gräsötippen utanför Köping är ett av dessa förorenade områden. Deponin har använts av både Yara AB och Köpings kommun mellan åren 1945-1975 och fungerat som deponi för både industri- och hushållsavfall. Syftet med denna rapport är att kartlägga vilka föroreningar som finns i mark och vatten i Gräsötippen och tolka föroreningarnas spridning. Utifrån den informationen ska deponin sedan riskklassas enligt MIFO. Målet är att rapporten ska kunna fungera som underlag för framtida åtgärdsplaner för Gräsötippen. För att få en bild över vad som har deponerats på Gräsötippen har anställda och före detta anställda vid Yara samt andra som har haft anknytning till Gräsötippen intervjuats. Grundvattenrör har installerats i och runtom deponin för att det skulle kunna tolkas hur grundvattnet rör sig under deponin och för att det skulle kunna tas prover på grundvattnet och jorden. De vatten- och jordprover som togs, analyserades med avseende på metaller, organiska föreningar och närsalter. Dessutom har en modellering utförts i VS2DI för att få en bild över grundvattnets flödesriktning och hastighet under deponin. I vattenproven detekterades endast bly över Naturvårdsverkets riktvärde samt relativt höga halter av närsalter. I jorden detekterades cancerogena PAHer, PCB, alifater, aromater, arsenik, bly, kadmium, kvicksilver och zink över Naturvårdsverkets riktvärden. Gräsötippen är bra placerad i ett område med tjock lera som förhindrar snabb spridning och idag lakas inga höga halter av föroreningar ut. Spridningen av föroreningar är liten, istället ligger de flesta föroreningarna fast i marken och sprids därmed inte till omgivningen. Vattenflödets huvudriktning från deponin är söderut, men det sker även flöden åt både väster och öster. Det finns i dagens läge en del förslag på åtgärder som bör utföras på Gräsötippen för att minska risken för framtida spridning och upprätthålla kontroll på det vatten som används i närområdet. Några av dessa åtgärder är att sluttäcka deponin, att analysera gräs och växter i hagen på deponin samt att kontinuerligt analysera vattnet i grundvattenrören och brunnarna på och runt Gräsötippen. Vid riskklassningen av Gräsötippen enligt MIFO, klassas den till riskklass 3, måttlig risk.

Due to various components within the landfill sites, the water qualityof landfill leachate, which has high consistency of COD, BOD and nutrients, is unsteady. Using traditional sewage treatment plant to treat leachate should be designed and built to fit the unsteady water quality, which is usually time consuming and high expenditured. Therefore, application of constructed wetland treatment systems as altanatives may solve such kinds of problems According to the experimental results of this study, referring to the effect of cleaning the controlling substances, the SSF (sub-surface flow system) constructed wetland system performed better than the FWS (free-water surface system) one, which was because FWS was usually operated in an opening water areas, which exposured to the air causing stink in the inflow site of influent, and meanwhile caused problems of virus-transmitting mosquitoes. . Thus, it was suggested to use SSF system in treating landfill leachate. In this study, we found that the average removal efficiencies of pollutants in the leachate were high in the constructed wetland systmes (phosphate 73%, total phosphorous 70¢H, total nitrogen 57%, NH3-N 77¢H, COD 43% ). In addition, the BOD in the effluent from the systems could reach the outflow standard guideline in Taiwan (30 mg/L). Hence, using constructed wetland systems to solve those problems arisen from landfill leachate is expandable. We also found that the aquatic plant species of reed (Phragmites australis) that we used in this study could not grow well and was invaded by aphid due to the limitary environment in the landfill site and lack of biodiversity, which could not generate a good natural food chain. On the other hand, it was found that the plant species of evergreen (Dracaena sanderiana) could grow healthily and present high removal efficiencies for pollutants. Since the leachate was lack of biodegradable organic carbon sources used for denitrification, in the final test run of this study, we run an experiment of adding organic carbon sourcecs (fructose and molasses) into the constructed wetland systemis to test its effect on denitrification. The experimental results showed that the addition of organic carbon sources could significantly increase the efficiencies of denitrification to let more nitrate removed from the leachate, especially for molasses, which could increase the denitrification efficiency above 90%.

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Tarek Abichou, Florida State University, College of Engineering, Dept. of Civil and Environmental Engineering. Title and description from dissertation home page (viewed June 21, 2004). Includes bibliographical references.

Thesis (M. Sc.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 121-123).

Arsenic is a naturally occurring contaminant in ground water. The link between human exposure to elevated levels of arsenic and the increase in cancerous and non-cancerous diseases is well documented. Consequently, arsenic removal from drinking water has been thoroughly investigated.Lowering the maximum contaminant limit of arsenic (from 50 to 10 ppb) will burden small water utilities, who either lack the financial or technical ability to comply. Adsorption onto solid media has been one of the most attractive options for small water utilities (EPA, 2001), but this process generates huge amounts of arsenic bearing solid residuals (ABSRs) complicating further this matter.Numerous studies have suggested that the Toxicity Characteristics Leaching Procedure (TCLP) does not properly reflect the actual leaching behavior of ASBRs under landfills (Ghosh et al., 2004). This work focuses on testing different arsenic iron- oxide and non- iron- based sorbents, likely to be used for arsenic removal, and assessing the long term behavior of these sorbents under landfill conditions. Our results indicate that microbial processes play a major role in the mobilization of As from granular ferric hydroxide (GFH). Long term operation of GFH sorbent showed that Fe (III) was reduced to Fe(II) and As(V) was reduced to As(III) under anaerobic/reducing conditions. Under semi batch landfill simulation experiments, our results show that non iron based media leached arsenic above the Toxicity Characteristics limit (TC) and it was observed that sorbate (As) might leach at a faster rate than the sorbent itself. It is thought that arsenic mobilization from iron-based sorbent occurs mostly due to iron reduction and its subsequent dissolution. However, measured arsenic leaching rates from the sorbents used in this study are comparable with that of the ferric hydroxide media, which indicates that the mechanism of arsenic mobilization might be independent of the possible dissolution of the sorbent. Despite the fact that non- iron based media may have a higher arsenic adsorption capacity, they leach arsenic at a higher rate than iron based media under our simulated landfill conditions.

The physical response of composite landfill liners consisting of a geomembrane on top of a geosynthetic clay liner (GCL) are examined under simulated landfill conditions. The deformation and strains of a 1.5-mm-thick high-density polyethylene geomembrane and thickness and hydraulic performance of a nominally 7-mm-thick GCL are quantified when the composite liner was buried beneath 50 mm coarse gravel, at applied pressures up to 1000 kPa, with a firm sand foundation layer, and with and without a wrinkle in the geomembrane. At an applied pressure of 250 kPa, with either no protection or conventional thick nonwoven needle-punched geotextile protection layers, the tensile strains in the geomembrane exceeded a 3% allowable limit and the GCL was reduced in thickness to as little as 2.2 mm from extrusion of bentonite beneath a gravel particle. Whereas a 150-mm-thick sand protection layer limited strains in the geomembrane to 0.1% and prevented extrusion in the GCL so that deformation was from bentonite consolidation and not from extrusion. A GCL with a thickness of less than 3 mm from extrusion was shown to be susceptible to failure from internal erosion of bentonite in the GCL at hydraulic head differences across the GCL between 1-10 m. Conversely with the sand protection layer, the GCL could withstand a head difference of greater than 100 m without any evidence of internal erosion. Further, the permittivity of an extruded 3.5-mm-thick GCL was found to be 4.5 times larger than a 7-mm-thick GCL that did not experience extrusion. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2008-09-05 10:47:21.783