Amount Of Leachate Research Articles

Coal Ash Triggers an Elevated Temperature Landfill Development: Lessons from the Bristol Virginia Solid Waste Landfill Neighboring Community

Landfills for disposing of solid waste are designed, located, managed, and monitored facilities expected to comply with government regulations to prevent contamination of the surrounding environment. After the average life expectancy of a typical landfill (30 to 50 years), a large investment in the construction, operation, final closure, and 30-year monitoring of a new site is needed. In this case study, we provide a holistic explanation of the unexpected development of elevated temperature landfills (ETLFs), such as that in the city of Bristol (United States) on the border of the states of Virginia and Tennessee, including the initial role played by coal ash. Despite the increasing frequency of ETLF occurrence, there is limited knowledge available about their associated environmental problems. The study uses mixed (qualitative, quantitative, and mapping) methods to analyze (1) the levels of odoriferous reduced sulfur compounds, ammonia, and volatile organic compounds (VOCs) emitted, (2) the ratio of methane to carbon dioxide concentrations in five locations, which dropped from unity (normal landfill) to 0.565, (3) the location of gas well heads with gradients of elevated temperatures, and (4) the correlation of the filling rate (upward of ~12 m y−1) with depth for registered events depositing coal ash waste. The work identifies spatial patterns that support the conclusion that coal ash served as the initiator for an ETLF creation. The case of the city of Bristol constitutes an example of ETLFs with elevated temperatures above the regulatory United States Environmental Protection Agency (EPA) upper threshold (65 °C), having alongside low methane emissions, large production of leachate, land subsidence, and a large production of organic compounds. Such landfills suffer abnormal chemical reactions within the waste mass that reduce the life expectancy of the site. Residents in such communities suffer intolerable odors from fugitive emissions and poor air quality becomes prominent, affecting the well-being and economy of surrounding populations. Conclusive information available indicates that the Bristol landfill has been producing large amounts of leachate and hazardous gases under the high pressures and temperatures developed within the landfill. A lesson learned, which should be used to prevent this problem in the future, is that the early addition of coal ash into the landfill would have catalyzed the process of ETLF creation. The work considers the public health risks and socioeconomic problems of residents exposed to emissions from an ETLF and discusses the efforts needed to prevent further incidents in other locations.

Highly efficient recovery of phosphate and fluoride from phosphogypsum leachate: Selective precipitation and adsorption

Phosphogypsum, a typical by-product in the phosphorus chemical industry, could generate a large amount of leachate containing phosphate and fluoride in the process of rainfall and long-term stacking, which not only causes serious environmental pollution, but also leads to a waste of resources. In this study, a united treatment of calcium hydroxide precipitation and lanthanum zeolite (La-ZFA) adsorption was proposed to achieve the recovery of phosphate and fluoride from phosphogypsum leachate. In phosphogypsum, most phosphorus could be leached except P in the residual occurrence form, while for fluoride, only water-soluble F could be effectively leached. The optimum leaching amounts of phosphate and fluoride were 22.59 and 4.64 mg/g, respectively, at liquid-solid ratio of 400:1, leaching time of 120 min, pH of 6.0, particle size of >200 mesh (<0.075 mm), and leaching temperature of 25°C. Using Ca(OH)2 as the precipitant, the phosphate could be precipitated selectively from phosphogypsum leachate by controlling pH and time, and the concentrations of it decreased significantly to 0.29 mg/L at pH 10.0, with a removal efficiency of 99.48%. XRD, SEM and Visual MINTEQ software analysis proved that the main component of the precipitate was hydroxyapatite (Ca5(PO4)3(OH)). After P precipitation, a series of sorbents for fluoride were investigated, and La-ZFA sorbent was chosen and utilized to recover the fluoride from the leachate through a cyclic fixed-bed column. The efficiency of La-ZFA was basically not affected by the high concentration sulfate, and it can selectively adsorb fluoride from phosphogypsum leachate, leading to a final fluoride concentration of 0.29 mg/L in the effluent. The characterization demonstrated that fluoride might be adsorbed onto the La-ZFA via ligand exchange with hydroxy groups. The proposed method in this study is expected to sequentially recover phosphate and fluorine from the leachate of phosphogypsum, and it has great guiding significance for resource utilization and management of phosphogypsum.

Continuous multicolumn ion exchange process for spent lithium-ion battery leachate: Recovery and purification of a Li+Ni+Co mixture

A continuously operated ion exchange process scheme for the recovery and purification of valuable metals from acid leachates of spent Lithium-ion battery cathodes was developed. The aim is to provide a versatile and industrially feasible alternative for liquid–liquid extraction and precipitation for recycling of spent Li-ion batteries. A chelating resin with aminomethylphosphonic acid functional group (Lewatit® MDS TP 260) was used in a laboratory-scale multicolumn configuration that combined counter-current and cross-current operations. The process was operated at 60 °C with a synthetic leachate with pH 1.8 as the feed. A two-step desorption procedure (1.0 M sulfuric acid (H2SO4) followed by 0.4 M potassium oxalate (K2C2O4)) was found to prevent accumulation of strongly bound metals in the resin. 1 M H2SO4 was found sufficient for regeneration. Pure raffinate containing Li, Ni, and Co was successfully separated from impurity metals (Mn, Cu, Al, and Fe). In steady state operation, no loss of ion exchange capacity was observed. The process was optimized experimentally with focus on the effect of fresh feed and eluent flow rates to increase the productivity and improve the recovery rates of the target metals while maintaining a raffinate purity of 100 %. Increasing the amount of leachate processed per switch was found to enhance the recovery of Co, Li and Ni due to the displacement effect. Very high recovery yields (96.97 % for Co, 99.15 % for Ni, and 100 % for Li) were achieved. The laboratory scale unit could process 1.64L(L·h)−1 of leachate to yield 34.04 g(L·h)−1 of Li+Ni+Co mixture in the raffinate. Moreover, Cu+Mn and Al+Fe rich extract streams with 84.74 % and 97.46 % purities were obtained as by-products. With respect to the recovery rates, the continuous ion exchange process is superior to batchwise operation of ion exchange columns, conventional solvent extraction and not to mention precipitation processes making it a viable alternative in hydrometallurgical LIB recycling.

Water balance estimation for an ordinary solid waste sanitary landfill in Costa Rica

To assess the necessity of treatment systems for leachate generated by ordinary solid waste deposited in a sanitary fill, accurate estimation of the leachate and gas amount produced during biodegradation process is essential. Climatic conditions at the site significantly influence leachate generation; therefore, accurate estimation of rainfall, temperature, solar radiation, and infiltration into the fill is imperative. In this study, we analyzed the water balance of the Miramar landfill in Costa Rica, assessed the amount of leachate produced using various methodologies, and then compared these findings with the field data to identify the best methodology for specific environmental conditions. To comprehensively analyze landfill behavior, as well as the leachate and gases generated from waste decomposition, determining the hydraulic properties of the materials inside the cells is necessary. These properties must consider variables such as the types of materials present at the site, age of the ordinary waste, and their densities. The hydraulic properties of the materials were obtained from various laboratory tests, which included determining the soil–water characteristic curve necessary for assessing unsaturated conditions in the solid waste. These properties are compared with the results of studies conducted in other landfills to validate the current methodology and the obtained results, which can be used for conducting studies on leachate generation or slope stability analysis for sanitary landfill slopes. The amount of leachate generated was estimated using the methodology proposed by Delgado A. (2018). Additionally, the Hydrologic Evaluation of Landfill Performance model (HELP V 4.0) was employed, demonstrating superior estimation compared to recorded field data. The HELP V 4.0 model facilitated the incorporation of different material layers and thicknesses, weather information at the site, slopes, and drainage conditions.

Variation in Seed Quality Paramertes of Off-Season Soybean of Different Planting Dates and Varieties

The work was carried out to assess the effect of varieties and dates of sowing on seed quality parameters of soybean seed produced during off-season i.e., Rabi at Rajendranagar. The seeds of varieties AISb-50, Basara and JS-335 were used for estimation of seed quality parameters which were sown on 15th December and 15th January. The seed quality parameters differed significantly due to dates of sowing and varieties. The treatment sum of squares revealed a significant difference in germination, seedling vigour index-I, seedling dry weight, speed of germination and field emergence, whereas seedling length was non-significant for varieties. While the seedling vigour index-II and electrical conductivity showed non-significant variation in the interaction between varieties and dates of sowing. The 15th December sown crop showed higher germination (91.11%), seedling length (27.63 cm), seedling vigour index-I (2518), dry weight (95.90 mg), seedling vigour index-II (8713), speed of germination (25.05) and field emergence (89.22%). The variety JS-335 exhibited higher germination (92.83%), seedling length (27.55cm), vigour index I (2558), speed of germination (28.25%), while higher seedling dry weight and vigour index II was exhibited by Basara (94.86 mg and 8097). The amount of leachates was found in Basara with electrical conductivity of 23.82 µScm-1g-1. The interaction between dates of sowing and varieties revealed that the variety JS-335 of 15th December sown exhibited higher germination (95.33%), seedling length (28.43 cm), seedling vigour index I (2711), speed of germination (29.97) among other varieties. The variety Basara of 15th December sown crop showed higher seedling dry weight (103.93 mg) and seedling vigour index II (8936). The electrical conductivity was higher in case of Basara of 15th January (24.59 µScm-1g-1).

Leachate indicators of an elevated temperature landfill

Elevated temperature landfills (ETLFs) are municipal solid waste (MSW) landfills that have been impacted by subsurface exothermic reactions (SERs) and display unusual gas and leachate composition. Leachate quantity and quality data were analyzed to identify indicators of a SER at an ETLF in Ohio, USA. ETLF leachate generation increased from 2.04 to 14.4 m3/hectare-day (218 to 1,539 gallons/acre-day), peaking 16 months after the reaction was first noticed. The leachate generation rate for this ETLF remains about two times greater than the average Ohio MSW landfill. Several general parameters such as pH, electrical conductivity (EC), and total dissolved solids (TDS) remain impacted 5 years later. Similarly, metals such as arsenic, iron, calcium, potassium, and magnesium have increased in concentration. Volatile organic compounds (VOCs) behavior was less consistent as a group of chemicals. Increases of VOCs such as acetone, benzene, and methyl ethyl ketone (MEK) also increased. Importantly, in one year, benzene exceeded its toxicity characteristic threshold meaning the leachate was a hazardous waste, substantially increasing treatment and disposal costs. It is not clear if the VOCs are produced directly by the SER or if they are an indicator that microbial processes -which would otherwise consume them- have been disrupted. ETLFs likely do not all undergo the same exothermic reaction(s) and, unlike the analysis of landfill gas composition, temporal changes in leachate constituents’ concentrations may be more important than comparing to absolute values.

Survey on the current leachate treatments of public municipal solid waste landfills and the potential impact of per- and polyfluorinatedalkyl substances in the Eastern and Northwestern United States

ABSTRACT Leachate from landfills can be a significant challenge to manage and treat due to conventional contaminants. The addition of emerging contaminants such as per- and polyfluorinatedalkyl substances (PFASs) makes treatment even more complex. PFASs enter landfills through consumer waste and have been detected in landfill leachates at varying concentrations. The design and decision-making on leachate treatment require essential information since it depends on local factors, e.g. climate, proximity to wastewater treatment plants, and waste type. This study conducted a survey on actively operated public municipal solid waste (MSW) landfills in the Eastern and Northwestern regions of the US to understand the current leachate treatment practices and views from public MSW landfill managers on PFAS treatment. The survey aims to explore the possible adaptations from the industry to the pending regulatory guidelines for the potential PFASs treatment. Results show the majority of the landfills are currently using off-site disposal (72% of the responses), followed by complete onsite treatment (18% of the responses) and pre-treatment onsite and off-site disposal methods (10% of the responses). The factors that guided the selection of treatment methods included climate, economics, and future regulations. Evaporation and recirculation were the most prevalent onsite treatment technologies for public landfills, which reduced the leachate quantity for treatment. The public landfills expressed awareness of the potential impact of PFASs on the changes in leachate treatment. The current state-level regulation, potential federal PFAS regulation, and treatment costs are raising awareness of the onsite treatment for PFASs. The results of this study will benefit the improvement of PFAS awareness and provide critical information that will directly affect the leachate treatment process for PFASs. Implications: This study presents a survey on the current leachate treatment process in the public municipal solid waste landfills in the eastern and northwestern U.S. and their potential process improvement on the impact of PFASs. This study is relevant to the topic of the JA&WMA because the research falls directly within the scope of this journal, and it documents the leachate treatment of landfills, and the results of this study will immediately contribute to our understanding of the waste treatment, benefiting the improvement of PFASs awareness, and providing critical information that will directly affect the leachate treatment process.

Lysimeter deep N fertilizer placement reduced leaching and improved N use efficiency

Deep fertilization has been tested widely for nitrogen (N) use efficiency but there is little evidence of its impact on N leaching and the interplay between climate factors and crop N use. In this study, we tested the effect of three fertilizer N placements on leaching, crop growth, and greenhouse gas (GHG) emissions in a lysimeter experiment over three consecutive years with spring-sown cereals (S1, S2, and S3). Leaching was additionally monitored in an 11-month fallow period (F1) preceding S1 and a 15-month fallow period (F2) following S3. In addition to a control with no N fertilizer (Control), 100 kg N ha−1 year−1 of ammonium nitrate was placed at 0.2 m (Deep), 0.07 m (Shallow), or halved between 0.07 m and 0.2 m (Mixed). Deep reduced leachate amount in each cropping period, with significant reductions (p < 0.05) in the drought year (S2) and cumulatively for S1-S3. Overall, Deep reduced leaching by 22, 25 and 34% compared to Shallow, Mixed and Control, respectively. Deep and Mixed reduced N leaching across S1-S3 compared with Shallow, but Deep further reduced N loads by 15% compared to Mixed and was significantly lowest (p < 0.05) among the fertilized treatments in S1 and S2. In S3, Deep increased grain yields by 28 and 22% compared to Shallow and Mixed, respectively, while nearly doubling the agronomic efficiency of N (AEN) and the recovery efficiency of N (REN). Deep N placement is a promising mitigation practice that should be further investigated.

Treatment of compressed leachate from refuse transfer stations by freeze-melt method

A small amount of leachate with complex composition will be produced during the compressing of municipal solid waste in refuse transfer stations. In this study, the freeze-melt method, a green and efficient wastewater treatment technology, was used to treat the compressed leachate. The effects of freezing temperature, freezing duration, and ice melting method on the removal rates of contaminants were investigated. The results showed that the freeze-melt method was not selective for the removal of chemical oxygen demand (COD), total organic carbon (TOC), ammonia-nitrogen (NH3-N) and total phosphorus (TP). The removal rate of contaminants was positively correlated with freezing temperature and negatively correlated with freezing duration, and the slower the growth rate of ice, the higher the purity of ice. When the compressed leachate was frozen at −15 °C for 42 h, the removal rates of COD, TOC, NH3-N and TP were 60.00%, 58.40%, 56.89% and 55.34%, respectively. Contaminants trapped in ice were removed during the melting process, especially in the early stages of melting. The divided melting method was more beneficial than the natural melting method in removing contaminants during the initial stage of melting, which contributes to the reduction of produced water losses. This study provides a new idea for the treatment of small amounts of highly concentrated leachate generated by compression facilities distributed in various corners of the city.

Separation Zone Required to Buffer Hazardous Waste Landfills Impact on Scattered Water Supply Sources: From a Whole Lifespan Perspective

Threats from landfill leachate leakage to groundwater quality in remote areas is a major concern globally. Buffering distance (BFD) maintained between landfill site and groundwater supply wells is important to prevent drinking water from contamination of hazardous pollutant. Ignoring the leakage increase in the end of landfill life leads to an underestimate of BFD demand, posing potential threat to drinking safety. This paper constructs a framework for BFD prediction with the consideration of landfill performance degradation by coupling landfill performance evaluation model with the aging and defect evolution model of landfill engineering materials, and carries out model application and verification in a coastal hazardous waste landfill. The results show that during the life cycle of a landfill, its BFD experienced a 1.5-time increase from the start of its operation to its life end and reached 3000 m. Under the condition of landfill performance degradation, the BFDs required to attenuate heavy metals experience more increase than those of organic pollutants; BFD required for zinc (Zn), for example, increases 720 m over the no-degradation condition, while 2,4-dichlorophenol(2,4-D) increases by only 288 m. Considering the uncertainty sourced from model parameter and structure, the BFD should be more than 4050 m to ensure long-term safe drinking under unfavorable conditions such as large amount of leachate, weak degradation and fast diffusion of pollutant in vadose and aquifer. If the BFD cannot meet the demand at the end of the landfill life, the leaching behavior of solid waste can be controlled to reduce it depending on BFD. For example, when the leaching concentration of Cd in the waste is reduced from 0.6 mg/L to 0.17 mg/L, the buffering distance is be reduced from 3000 m to 500 m.

Mathematical modeling and numerical simulation technique for selected heavy metal transport in MSW dumpsite

The study focused on development of mathematical modeling and numerical simulation technique for selected heavy metal transport in Uyo municipal solid waste dumpsite in Akwa Ibom State to investigate the level in depth to which leachate from the dumpsite extends and the quantity of leachate at various depth of the dumpsite soil. Uyo waste dumpsite is operating open dumping system where provisions are not made for preservation and conservation of soil and water quality, hence, the need for this study. Three monitoring pits within Uyo waste dumpsite were constructed and infiltration runs were measured, and soil samples were collected beside infiltration points from nine designated depths ranging from 0 to 0.9 m for modeling heavy metal transport in the soil. Data collected were subjected to descriptive and inferential statistics while the COMSOL Multiphysics software 6.0 was used to simulate the movement of pollutants in the soil. It was observed that heavy metal contaminant transport in soil of the study area is in the power functional form. The transport of heavy metals in the dumpsite can be described by a power model from linear regression and a numerical model based on finite element. Their validation equations showed that the predicted and the observed concentrations yielded a very high R2 value of over 95%. The power model and the COMSOL finite element model show very strong correlation for all selected heavy metals. Findings from the study has identified level in depth to which leachate from the dumpsite extends and the quantity of leachate at various depth of the dumpsite soil which can be accurately predicted using leachate transport model of this study.

Comparative evaluation of the results of chemical analysis of the solid municipal waste filtrate at the Irkutsk landfill

Heavy metals are widespread chemical elements, many of which are toxic components polluting the biosphere. They include more than 40 are priority pollutants. Every year the danger of their getting them into the soil is increasing. A powerful source of release of harmful heavy metals into the environment are municipal solid waste (MSW) dumps. There are dozens of such these landfills in Irkutsk region, including the largest landfill in Irkutsk. In 2014 and 2019, on the territory of this landfill the landfill leachate was analyzed for the content of general chemical and toxic components. The comparative analysis showed that the landfill soil is extremely dangerous. The excess of MPC of heavy metals in the filtrate ranged from 2.4 to 67.6. The article presents the results of the analysis of landfill leachate taken in 2021 in the sanitary protection zones, and compared with the previously obtained data. It was established that the chemical and biochemical processes between various components of landfill leachates cause the formation of toxic compounds and become sources of infection. Precipitation forms a large amount of leachate which has significant concentrations of especially toxic substances, which inevitably enter the groundwater. In addition to harmful compounds and heavy metals, wastewater also contains pathogenic microorganisms.

EVALULATION OF A DROPLET SPRAYING/MISTING SYSTEM TO ENHANCE LEACHATE EVAPORATION AND REDUCE LEACHATE TREATMENT COSTS: A CASE STUDY AT THE THREE RIVERS SOLID WASTE AUTHORITY LANDFILL

Three Rivers Solid Waste Authority (TRSWA) operates a MSW landfill outside Jackson, South Carolina at which leachate is stored in a collection pond then trucked to a local wastewater treatment plant (WWTP) for treatment. This landfill operates a droplet spraying/misting system (referred to as the Lilypad system) to enhance leachate evaporation and ultimately reduce the quantity of leachate in the pond that requires subsequent treatment. Little work investigating the efficacy in using such a system to enhance leachate evaporation has been reported. The overall goal associated with this study was to quantify the amount of evaporation enhanced by the droplet spraying system and evaluate how the economics of the enhanced leachate evaporation compare to hauling leachate to a WWTP. This was accomplished by performing a water balance on the pond, developing a simple model to link leachate evaporation to the droplet spraying system, and performing an economic evaluation of the system. Overall, results from this work indicate the use of a droplet spraying/misting system to enhance leachate evaporation at on-site storage/collection ponds is effective, resulting in between 2.1 to 2.6 times more evaporation than what would occur naturally. In addition, the economic evaluation of this system indicates that operating the Lilypad system at maximum speed/flow for the greatest number of hours results in saving up to 7% of the total cost when compared to no operation of the Lilypad system.

Critical review for the quantification of leachate production: Evaluation example for the “Oum Azza” public landfill in Rabat city, Morocco

AbstractThe estimation of leachate quantities produced in landfills is necessary to dimension the treatment plants allowing to reduce the polluting load of these effluents and consequently avoid their negative impacts on the environment. Different leachate quantification methods were used in this study to assess the leachate volume produced at the Oum Azza landfill. The water balance method give comparable estimations of leachate production to the Ouled Berjal landfill ratio. The first method showed average values between 487 and 495 m3/day for 2015, 2018, and 2019, and at the same time, the second method gave values between 470 and 477 m3/day for the same years. In contrast, the World Bank ratio showed high values that vary between 2260 and 2295 m3/day for 2015, 2018, and 2019. The on‐site data and the statistical analysis showed us that the World Bank ratio is not adapted for the estimation of the leachates produced in Oum Azza landfill, while the water balance and the ratio of Ouled Berjal landfill allowed to give comparable results to reality.

Effect of Sludge Content on the Decomposition of Different Types of Food Waste

Food waste, which is the second largest component in landfills, generates excessive amounts of leachate and greenhouse gas. As a result, it has recently become a severe concern, mostly in the developing countries for its adverse impact on the environment. The addition of nutrients to organic waste limits the accumulation of volatile fatty acid (VFA) and accelerates the production of energy from food waste. The objective of the current study is to find out the effects of sludge addition on the decomposition and gas generation of separate components of food waste. This study was conducted for four combinations of reactors: two pairs containing meat and grain with the addition of a sludge content of 20% and 30%, respectively, as inoculum; another two pairs of reactors containing fruits and vegetables with a sludge content of 20% and 30%, respectively. Over the operation period, pH, volume, COD, and VFA tests were conducted for leachate while composition and volume measurements were done for the generated gas. Based on the results, it is observed that addition of sludge accelerated the decomposition of fruit and vegetable waste due to limited VFA accumulation compared to meat and grain. The maximum methane production was found in fruits and vegetable reactors at a rate of 6.7 L of methane per pound of food waste. For fruit and vegetable reactors, the CH4:CO2 ratio increased to as high as 8.5. On the other hand, for the meat and grain reactors, the increase in CH4:CO2 ratio was insignificant as they were in the lag phase.

Bench scale percolation tests on radioactive Cs-contaminated soil in Fukushima and soil modified with water-absorbing polymer agent

The reuse of removed soil generated from decontamination projects in Fukushima as a recycled material for the construction of embankments has been under consideration for the sake of reducing the volume of this soil for its final disposal. Agents containing water-absorbing polymers are used in Fukushima to modify the removed soil in order to increase the separation efficiency of foreign materials and to improve the easiness of handling. As the reuse of modified soil containing organic water-absorbing materials, such as a superabsorbent polymer, is rather rare in the geotechnical field, it necessitates an investigation into the impact of the modifying agent on the leachate quality to ensure the environmental safety of the recycling project. In this study, therefore, bench scale percolation tests were conducted to examine the changes in the leachate quality of the removed soil with and without modification by an agent containing a superabsorbent polymer. The tests lasted for more than 950 days (liquid/solid ratio of over 10). The peak 137Cs concentration in the leachate from the removed soil was 8.6 Bq/L and the accumulated leaching ratio was 0.243 %. The leaching of 137Cs from the modified soil decreased by 60 % after mixing the removed soil with a 3 % water-absorbing polymer agent. The leaching of K+ and ammonia nitrogen (NH4+-N) was 40 % and 60 % lower, respectively, after the soil modification, while the accumulated amount of leaching of the dissolved organic carbon in the initial stage was 60 % higher. The total leachate amount collected from the modified soil was 4 % lower than that collected from the removed soil.

Wood modification with phenol urea formaldehyde (PUF) resin: the influence of wood species selection on the dimensional stability

Wood modification is an excellent way to improve material properties, prolong service life, and pave the way for new applications for timber in the built environment. The aim of this study is to establish the influence of wood species in the modification process with phenol urea formaldehyde resin. Seven hardwoods and four softwoods were compared in an identical treatment. Since the wood species is the main variable, the study provides a clear insight as to its influence on modification—something not previously investigated. Small wood blocks of all eleven species were impregnated with low-molecular weight phenol urea formaldehyde resin and were subsequently heat-cured at 150 °C. Mass and dimensions of specimens were carefully monitored throughout three cycles of oven-drying and water-soaking to determine anti-swelling efficiency, bulking coefficient, and swelling coefficient. The results showed a clear relationship between density, bulking-, and swelling coefficients. Beyond this well-known relationship it was observed that species with similar density (e.g., lime and sycamore) had significantly different bulking coefficients and anti-swelling efficiencies. Reasons for these differences, which are independent of density, are discussed. The soaking solution was analysed to determine the nature of leached substances showing a correlation between the amount of leachate and the UV-absorbance (272 nm) of the solution.

Thermal effects of the hydraulic conductivity and threshold gradient of sand–clay liners in municipal solid waste landfills

High leachate heads and dry cracking of clay barriers are common problems in landfills. The use of sand-clay barriers with a non-darcy percolation patterns can not only prevent leakage of large amounts of leachate but can also potentially reduce the development of dry fractures due to loss of water. Thus, it has been suggested that sand-clay materials could be used as barriers at the bottoms of landfills or as a vertical barriers. However, biochemical degradation of waste in a landfill generates much heat, and the temperature can reach 60 °C. A high-temperature field can inevitably affect the permeability of sand-clay barriers. The change in sand-clay barrier permeability under the influence of temperature has received increasing attention. Therefore, in this study, a temperature-controlled permeameter with flexible walls was used to conduct experiments on permeability of sand-clay mixtures at four temperatures. The results indicated that the hydraulic conductivity gradually increased and the threshold gradient gradually decreased with increasing temperature. The hydraulic conductivity and threshold gradient exhibited exponential relationship with the temperature, respectively. Experiments were designed to measure changes in the permeate viscosity at different temperatures. The previously established hydraulic conductivity equation (that considered only the influence of temperature on the permeate viscosity) greatly differed from the measured values. In contrast, the newly established hydraulic conductivity equation (that considered the influence of temperature on both the permeate viscosity and intrinsic permeability) agreed well with the measured values. Statistics based on a large amount of data (collected previously) showed that the intrinsic clay permeability exhibited a power law relationship, with increasing temperature to a threshold gradient at 25 °C (Eq. (9)). Above the threshold, the intrinsic permeability experimental data increasingly deviated from Eq. (9). To consider the effect of the temperature on both the intrinsic permeability and permeate viscosity, an equation for calculation of the threshold gradient was proposed, and it could be found that the calculated values suitably agreed with the measured values. The results of this study provide an important theoretical basis and data to support the development of high-performance barriers with long service life for landfills.

Evaluation of the performance of a drainage geocomposite in a simple cover system based on 10 year measurements

In the course of the geotechnical investigations for a new runway at Munich Airport the hydro-mechanical behaviour of organogenic clays was studied. With the aim of an efficient use of materials the organogenic clay shall be used for noise and view barriers. As the organogenic clays have increased arsenic contents the percolation of such structures should be minimized. For the detailed investigation of the hydro-mechanical behaviour and for the determination of seepage quantities, a large scale, 5 m high, 30 m long and 25 m wide test fill was constructed. Due to the low permeability of the organogenic clays in compacted condition a cover design with a drainage mat and a top layer without an additional sealing layer was chosen. Measurements of the water balance were collected since the installation in 2008. The results show very low leachate quantities, although humid climatic conditions with average annual precipitation of approx. 745 mm were present. The low leachate rates can be mainly attributed to the capillary-breaking effect of the drainage geocomposite and the high water retention capacity of the topsoil. Based on the results the presented simple cover system can be considered an efficient and effective solution for minimizing infiltration water into core materials of embankments and noise barriers in road-way design.

Modeling leachate generation: practical scenarios for municipal solid waste landfills in Poland

The idea of water balance calculations within the landfill is to determine the distribution of water input and output, and finally the volume of leachate generated. The scope of this data is essential for rational planning of water and wastewater management, and designing leachate drainage network and leachate treatment systems. The aim of this study was to assess the possible amounts of leachate generation regarding ten different scenarios of landfill sealing systems. The calculations were performed using the Hydrologic Evaluation of Landfill Performance (HELP) model. It was revealed that the greatest share among the components of water balance in the landfill has precipitation (on average 509 mm in the 5-year period of simulation), together with evapotranspiration (on average 391 mm in the 5-year period of simulation). The study shows that the minimum amount of leachate (797–803 m3/year) occurs when the best placement quality (=5) is regarded for the geomembrane installed in the bottom of the landfill. The maximum leachate generation (830 m3/year) was found for those scenarios in which only three layers of bottom sealing systems were adopted, with the worst placement quality (=1) assigned to geomembranes. The results of this study confirm that the application of multilayer sealing systems has visible impact on the reduction of leachate generation of around 33 m3/year.