Pyrite formation driven by MSW landfill leachate in the Madrid Basin, Spain

The role of municipal solid waste (MSW) landfill leachate on the genesis of minor amounts of pyrite associated with gypsum in an otherwise predominantly evaporitic sequence was studied in geological and geochemical terms. The potential association between landfill leachate and the conditions required for bacterial reduction of sulfate and fixation of H₂S as pyrite were examined. The lithological column was generally found to contain little or no Fe. The δ³⁴S values for sulfates were consistent with previously reported data; however, the measured δ¹⁸O values were slightly higher. Sulfides disseminated in the marl/lutite exhibited higher δ³⁴S values (≈−8‰) than gypsum-coating pyrite crystals (δ³⁴S < −30‰). Dissolution of gypsum to sulfate and the supply of metabolizable organic matter and Fe required for H₂S fixation as sulfides may have originated from landfill leachate. Intermittent availability of leachate, a result of the precipitation regime, can facilitate sulfur disproportionation and lead to fractionations as high as      

Tunisian landfill leachate treatment using <Emphasis Type="Italic">Chlorella</Emphasis> sp.: effective factors and microalgae strain performance

The potential of the autoclaved Tunisian landfill leachate treatment using microalgae (Chlorella sp.) cultivation was investigated in this study. Landfill leachate was collected from Borj Chakir landfill, Tunisia. A full factorial experimental design 2² was proposed to study the effects of the incubation time and leachate ratio factors on the organic matter removal expressed in chemical oxygen demand (COD) and ammoniacal nitrogen (NH₄─N) and on the biological response of Chlorella sp. expressed by the cell density and chlorophyll content. All experiments were batch runs at ambient temperature (25 ± 2 °C). The Chlorella sp. biomass and chlorophyll a concentrations of 1.2 and 5.32 mg L^?1, respectively, were obtained with 10% leachate spike ratio. The obtained results showed that up to 90% of the ammoniacal nitrogen in landfill leachate was removed in 10% leachate ratio spiked medium with a residual concentration of 40 mg L^?1. The maximum COD removal rate reached 60% within 13 days of incubation time indicating that microalgae consortium was quite effective for treating landfill leachate organic contaminants. Furthermore, with the 10% leachate ratio spiked medium, the maximum lipid productivity was 4.74 mg L^?1 d^?1. The present study provides valuable information for potential adaptation of microalgae culture and its contribution for the treatment of Tunisian landfill leachate.     

Hydrogeology and historical assessment of a classic sequential-land use landfill site,Illinois, U.S.A.

The Blackwell site in northeastern Illinois was a classic sequential-use project combining land reclamation, a sanitary landfill, and a recreational park. This paper adds a recent assessment of leachate generation and groundwater contamination to the site's unfinished record. Hydrogeological studies show that (1) the landfill sits astride an outwash aquifer and a till mound, which are separated from an underlying dolomite aquifer by a thin, silty till; (2) leachate leaks from the landfill at an estimated average rate between 48 and 78 m³/d; (3) the resultant contaminant plume is virtually stagnant in the till but rapidly diluted in the outwash aquifer, so that no off-site contamination is detected; (4) trace VOC levels in the dolomite probably indicate that contaminants have migrated there from the landfill-derived plume in the outwash. Deviations from the original landfill concepts included elimination of a leachate collection system, increased landfill size, local absence of a clay liner, and partial use of nonclay cover. The hydrogeological setting was unsuitable for the landfill as constructed, indicating the importance of detailed geological consideration in landfill and land-use planning.     

Analysis of flow behavior in a landfill with cover soil of low hydraulic conductivity

 This paper presents the results of field tests of hydrologic parameters in a landfill and the results of numerical simulation to find the efficiency of the pumping method to reduce leachate levels in the landfill. The field hydraulic conductivity and storativity of waste and buried cover soils in the landfill are measured by pumping and slug tests. The hydrologic condition inside the landfill is first calibrated using the drawdown-time curve obtained from the pumping test, and the flow behavior of leachate during pumping in the landfill, when various layers of waste and buried cover soil exist, is analyzed through three-dimensional numerical simulation of flow. The results of the field investigation show that the buried cover soil of low hydraulic conductivity forms an impermeable layer preventing the downward flow of leachate and upward flow of landfill gas. The hydraulic conductivities of the pumping test and slug tests were quite close on the same order of magnitude. It was also possible to match the drawdown-time data of the field tests with those of the model using input data close to the hydrologic property obtained from the field tests. The numerical flow analysis showed that pumping was possible up to 120 tons/day for a single well without a drain, while the pumping rate could be increased to 300 tons/day for the same well with the drain. From the vertical section of the flow vector with a horizontal drain, the barrier role of buried cover soil is identified, which was proposed by examining the water contents of the disposed cover soil and waste in the field. Received: 15 May 1998 · Accepted: 4 January 1999     

Analysis of the distribution of inorganic constituents in a landfill leachate-contaminated aquifer: Astrolabe Park,Sydney, Australia

An investigation was conducted at Astrolabe Park landfill, a decommissioned municipal landfill in Sydney, Australia, to assess the physical and chemical processes affecting the distribution of inorganic constituents in the leachate plume. The plume is migrating from the landfill towards a groundwater-fed pond into which leachate-impacted groundwater discharges. Borehole geophysical logging and depth-discrete groundwater sampling were used to delineate the distribution of the leachate plume along two groundwater flow paths between the landfill and the shore of the pond. Borehole geophysical logs indicate a strong correlation between bulk and fluid electrical conductivity (EC) values, and help to identify small-scale heterogeneities that comprise a major constraint on contaminant transport within the aquifer. Variations in the distribution of several indicator parameters (EC, HCO₃^–, pH, Eh, NH₄⁺/NO₃^–, S^2–/SO₄^2–) are used to assess the dominant processes affecting contaminant distribution along the flow path, including mixing of fresh and contaminated groundwater, oxidation/reduction reactions and ion exchange.     

Treatment of leachate from domestic landfills with three-stage physicochemical and biochemical technology

Because domestic landfill leachate concentrates complex organic pollutants, effective treatment of landfill leachate has gained increasing attention in recent years. In this paper, three-stage physicochemical and biochemical technology for treatment of domestic landfill leachate is presented. Based on an eight-month pilot operation, over 96% of the main pollutants, for example COD_Cr, BOD₅, SS, NH₄ ⁺–N, coliform, and chrominance, can be removed, among which the removal efficiency of COD_Cr was 89.5, 8.6, and 1.7% in stages 1, 2, and 3, respectively, and the removal efficiency of BOD₅ was 90.3, 8.3, and 1.4%. In the treatment, the biochemical process played a principal role on the removal of pollutants from the leachate. The treatment efficiency depends on how the syntheses of physicochemical, anaerobic, and hydrolytic procedures pave the way for biochemical treatment. Application of a combined efflux and mixed-flow aerator enhanced the removal efficiency during each procedure.     

垃圾渗滤液水溶性有机物对污染土壤中重金属Pb迁移性的影响

采用土柱淋滤试验研究了不同填埋年限的垃圾渗滤液DOM在土壤中垂直迁移及其对土壤重金属Pb淋滤溶出的影响。结果表明,不同填埋年限(0.4~5.12 a)的垃圾渗滤液DOM在土壤中垂直向下的迁移速率存在差异,填埋时间短的垃圾渗滤液DOM在土壤中迁移性较强。与对照相比(不加渗滤液DOM),垃圾渗滤液处理对红壤中土壤重金属Pb的累积解吸率高74.25%;在潮土上高-38.79%,且垃圾填埋年限中期的渗滤液DOM对土壤重金属的溶出影响更显著,说明垃圾渗滤液DOM进入土壤环境对重金属的迁移有促进作用。     

Environmental impact of an urban landfill on a coastal aquifer (El Jadida, Morocco)

The El Jadida landfill is one among many uncontrolled dumping sites in Morocco with no bottom liner. About 150 tons/day of solid wastes from mixed urban and industrial origins are placed directly on the ground. At the site of this landfill, the groundwaters circulate deeply (10–15 m) in the Cenomanian rock (calcareous–marl), which is characterised by an important permeability from cracks. The soil is sand–clay characterized by a weak coefficient of retention.The phreatic water ascends to the bottom of three quarries, which are located within the landfill. These circumstances, along with the lack of a leachate collection system, worsen the risks for a potential deterioration of the aquifer.To evaluate groundwater pollution due to this urban landfill, piezometric level and geochemical analyses have been monitored since 1999 on 60 wells. The landfill leachate has been collected from the three quarries that are located within the landfill. The average results of geochemical analyses show an important polluant charge vehiculed by landfill leachate (chloride = 5680 mg l⁻¹, chemical oxygen demand = 1000 mg l⁻¹, iron = 23 000 μg l⁻¹). They show also an important qualitative degradation of the groundwater, especially in the parts situated in the down gradient area and in direct proximity to the landfill. In these polluted zones, we have observed the following values: higher than 4.5 mS cm⁻¹ in electric conductivity, 1620 and 1000 mg l⁻¹ respectively in chlorides and sulfate (), 15–25 μg l⁻¹ in cadmium, and 60–100 μg l⁻¹ in chromium. These concentrations widely exceed the standard values for potable water.Several determining factors in the evolution of groundwater contamination have been highlighted, such as (1) depth of the water table, (2) permeability of soil and unsaturated zone, (3) effective infiltration, (4) humidity and (5) absence of a system for leachate drainage. So, to reduce the pollution risks of the groundwater, it is necessary to set a system of collection, drainage and treatment of landfill leachates and to emplace an impermeable surface at the site of landfill, in order to limit the infiltration of leachate.     

Investigation on potential groundwater impacts and influence of local hydrogeology on natural attenuation of leachate at a municipal landfill

The influence of local hydrogeology on natural attenuation of contaminants from landfill leachates in shallow aquifer underlying the active Olusosun landfill base in Lagos was investigated. In addition, the level of groundwater contamination in the vicinity of the landfill and of leachate migration pattern in groundwater down gradient of the landfill base was equally assessed. Landfill leachate and groundwater samples were collected and analyzed and characterized. Physico-chemical analyses of sampled water followed standard analytical methods. Analytical results showed a measurable impact of leachate outflows on groundwater quality. Elevated levels of anions: nitrate, chloride and sulphate in the groundwater body and heavy metals: Cr₃. Cd and Cu, were detected at measurable levels in groundwater down gradient of the landfill location without any particular attenuation pattern. The migration pattern and dispersion of leachates down gradient, 750 m away from the landfill location are irregular and difficult to predict as depicted by levels of contaminants present in groundwater. The study highlighted the importance of soil stratigraphy beneath the landfill base as an important factor in the natural attenuation of leachate constituents in the groundwater body.     

Attenuation of landfill leachate at two uncontrolled landfills

Attenuation characteristics of landfill leachate were examined for two uncontrolled landfills in Korea. The two landfills containing municipal wastes without appropriate bottom liner and leachate treatment system have different landfill age, waste volume, and most importantly different hydrogeologic settings. One landfill (Cheonan landfill) is situated in an open flat area while the other (Wonju landfill) is located in a valley. Variations of various parameters including dissolved organic carbon (DOC), dissolved oxygen (DO), alkalinity, pH, electrical conductivity (EC), redox potential (ORP), ammonia (NH₃), nitrate (NO₃⁻), sulfate (SO₄²⁻), and chloride (Cl⁻) were examined along groundwater flow path. All these parameters were analyzed every month for a year. In the interior of the landfills, typical anaerobic conditions revealed by low DO and NO₃ concentrations, negative ORP values, high NH₃, alkalinity, and Cl⁻ concentrations were observed. Generally, higher levels of contaminants (DOC, NH₃, and Cl⁻) were detected in the dry season while they were greatly lowered in the wet season. Significantly, large decrease of Cl^- concentration in the wet season indicates that the dilution or mixing is one of dominant attenuation mechanisms of leachate. But detailed variation behaviors in the two landfills are different and they were largely dependent on permeability of surface and subsurface layers. The intermediately permeable surface of the landfills receives part of direct rainfall infiltration but most rainwater is lost to fast runoff. The practically impermeable surface of clayey silt (paddy field) at immediately adjacent to the Cheonan landfill boundary prevented direct rainwater infiltration and hence redox condition of the ground waters were largely affected by that of the upper landfill and the less permeable materials beneath the paddy fields prohibited dispersion of the landfill leachate into down gradient area. In the Wonju landfill, there are three different permeability divisions, the landfill region, the sandy open field and the paddy field. Roles of the landfill and paddy regions are very similar to those at the Cheonan. The very permeable sandy field receiving a large amount of rainwater infiltration plays a key role in controlling redox condition of the down gradient area and contaminant migration. This paper reports details of the attenuation and redox conditions of the landfill leachates at the two uncontrolled landfills.     

The use of strontium and lead isotopes to identify sources of water beneath the Fresh Kills landfill,Staten Island,New York,USA

A study was undertaken to explore whether the isotopic compositions of Pb and Sr are useful to distinguish mixtures of uncontaminated groundwater, seawater, and landfill leachate at the Fresh Kills landfill, Staten Island, New York. Ratios of ⁸⁷Sr/⁸⁶Sr ranged from 0.7088 to 0.7137 and could be used to distinguish Sr that was derived from seawater from that in uncontaminated groundwater. Lead isotopic abundances did not vary systematically among the different water sources. Plots of ⁸⁷Sr/⁸⁶Sr versus dissolved organic C, B, and NH₄⁺ defined perpendicular trends, documenting where leachate or sea water mixed with uncontaminated groundwater, and demonstrating that leachate has not contaminated groundwater in aquifers beneath the landfill.     

Measuring the waterbalance of a three-layer cover of a domestic waste landfill

A covering system is described that is to be installed at a domestic waste landfill to reduce the generation of leachate.

The covering system consists of three parts: 1.5 m top- and subsoil, 0.5 m barrier layer and 0.3 m gas drainage layer. The waterbalance of the covering system is measured by two large-scale lysimeters (9.5 X 16.5 m) and soil moisture measurements with neutron moisture probe.     

垃圾填埋处理场渗滤液污染地下水的防治途径探讨

通过分析天水市麦积区老虎沟垃圾填埋处理场地质环境,结合挥发酚（C6H5OH）弥散试验资料,对垃圾处理场渗滤液中C6H5OH的运移特征、污染地下水机理进行了探讨,为垃圾填埋处理场有效防渗提供了设计依据。     

Electro-coagulation treatment of raw and autoclaved landfill leachate with aluminum electrodes: case study of Djebel Chakir (Tunisia)

Landfilling is a common practice worldwide for solid waste management. The leachate generated at landfill sites contains various organic and inorganic pollutants while it should be treated properly. In this study, the electrocoagulation (EC) process was recognized for its simplicity and effectiveness which was used for the treatment of leachate from the Djebel Chakir landfill site in northern Tunisia. In addition, we investigated the effect of microorganisms (e.g., bacteria, fungi, spore) on sludge production by the application of autoclaving treatment on raw leachate. The application of low current density (15 mA/cm²) within 2 h of treatment and using Al-Al electrodes revealed significant improvement of performance when autoclaving was applied. The chemical oxygen demand (COD) and nitrogen removal increased from 39 to 64% and from 13 to 30%, respectively. The sludge volume was reduced from 40 to 10%, and thus, its handling and disposal costs would be significantly decreased. The energy consumption rate was stable after 40 min of treatment at about 0.8 kWh/kg COD removed. Our study shows that removal of microorganisms by autoclaving prior to the EC process is promising for landfill leachate treatment. However, since autoclaving is far from being practical and cost-effective at full-scale plant, research on coupling EC with an alternative disinfecting process might be of great interest.     

Analyses on a high leachate mound in a landfill of municipal solid waste in China

The leachate levels in the landfills in southern China are generally high. Field monitoring was carried out in the Suzhou landfill to investigate the leachate mound. The saturated hydraulic conductivity and soil–water characteristic curve (SWCC) of municipal solid waste were measured using samples taken from different depths of the landfill. Field monitoring reveals that a perched leachate mound and a substantial main leachate mound existed in the landfill. The saturated hydraulic conductivities of wastes in shallow, middle and deep depth were measured to be 4.81 × 10^?2, 3.50 × 10^?3 and 3.56 × 10^?4 cm/s, respectively. The results of SWCC tests show that the SWCC curve was steep when matric suction was low, and the shallower the waste the steeper would be the curve. In addition to the field and laboratory tests, an unsaturated–saturated seepage analysis was conducted to simulate the development of the high leachate mound and to calculate the annual leachate production. The simulated volumetric water content in the unsaturated zone was about 40 %, which agreed well with the test result. The calculated leachate mound was consistent with the field measurement. The calculated annual and daily leachate productions were all more reasonable than the results of the HELP model.     

Experimental and Modelling Approaches for the Assessment of Chemical Impacts of Leachate Migration from Landfills: A Case Study of a Site on the Triassic Sandstone Aquifer in the UK East Midlands

Current risk-based methods for assessing the effects of landfill leachate migration on groundwater resources are conservative and generalised. Cost-effective and practical strategies are required which can robustly determine the potential for contaminant attenuation on a site-specific basis. In this paper laboratory column experiments and reactive transport modelling are evaluated as a combined approach for assessing the chem’ical impact of leachate migration in the Triassic Sandstone aquifer. The results are compared with field data for a landfill in the East Midlands. Columns of aquifer sandstone were flushed sequentially with groundwater, followed by acetogenic or methanogenic leachate to simulate chemical interactions occurring during leachate loading episodes. The key contaminants in leachate (NH₄, heavy metals, organic fractions) were attenuated by ion exchange, redox reactions, sorption and degradation. These processes produce a consistent hydrochemical signature which may help identify the extent of leachate migration in the aquifer. The laboratory results largely replicate those found in the field system, and the behaviour of inorganic contaminants during leachate flushing of the aquifer columns can be described by the reactive transport model. The experimental and modelling approach presented represents a powerful tool for risk assessment and prediction of leachate contaminant fate at unlined and lined landfills.     

土壤与地下水污染的地球物理地球化学勘查

列举了土壤、地下水中常见的有机和无机污染组分.进入地下水中的绝大部分污染物与介质发生物理化学反应后,各种金属、非金属离子、固体溶解物、盐类在地下潜水面附近逐渐浓集,导电性增强,电阻率明显降低,对电磁波的反射能力增强.经实际检测发现,某垃圾填埋场被垃圾渗漏液污染的土壤视电阻率在10 Ω·m左右,垃圾渗出液的实测电阻率在0.40 Ω·m左右.比较高密度电阻率法、瞬变电磁法、探地雷达法的效果后发现,高密度电阻率法的效果显著.荧光光谱和吸附乙烷、游离甲烷对指示储油气设施泄漏有显著效果,实际应用中,检测游离甲烷可快速圈定污染范围.     

Pilot-scale field model tests for detecting landfill leachate intrusion into the subsurface using a grid-net electrical conductivity measurement system

The grid-net electrical conductivity measurement system for detecting exact locations of landfill leachate intrusion in the subsurface was developed in this study. Laboratory and pilot-scale field model tests were performed to evaluate the direct application of a grid-net electrical conductivity measurement system for the detection of landfill leachate. A significant increase in electrical conductivity of soil was observed by adding landfill leachate. This can be explained as an increase in electrical conductivity of pore fluid due to an increase in leachate constituents as charge carriers. In pilot-scale field model tests, leachate intrusion locations were accurately identified at the initial stage of landfill leachate release by the grid-net electrical conductivity measurement system. The electrical conductivity of the subsurface before leachate injection lay within a small range of 24.8–43.0 S/cm. The electrical conductivity values in detected points were approximately ten times more than the conductivity values of the subsurface without landfill leachate intrusion. The results in this study indicate that the grid-net electrical conductivity measurement method has a possible application for detecting locations of landfill leachate intrusion into the subsurface at the initial stage, and thus has great potential in monitoring leachate leakage at waste landfills.     

Field-monitored settlement and other behavior of a multi-stage municipal waste landfill, Korea

The behavior of the Gimpo #2 landfill, which is an active landfill and the largest in Korea, is analyzed using field measurement data obtained from various field instruments installed within the landfill. The data included in this analysis are the leachate head within the landfill, waste load data using soil pressure plate and settlement data from settlement plate on the surface of the waste of each stage fill including the settlement of the soft foundation clay soil. Landfill blocks are selected both near the embankment and in the center area of the landfill. The analysis of the field-monitored data showed that the leachate head increase was negligible near the embankment. It was significant in the central block as the waste loads increase and reached 15 m at the fourth stage of waste disposal. The reason that the leachate head is higher in the central block than near the embankment is due to the long drainage path and the loss of gradient of drain pipes. The range of unit weight of the waste converted from the measurement data of earth pressure cell was 0.91–1.24 t/m³ and the average value was 1.05 t/m³. The values reflect well the waste compositions recently buried in GML #2, since from 1998 the waste disposed in GML #2 did not contain food waste. The magnitude of final settlements that occurred in each stage loading of 5 m thickness in the peripheral block was very close to 120 cm. The settlement rate of the waste by dividing the thickness of waste was 24 %. This rate can be divided into 10 % by waste loading and 14 % by waste decomposition. The delay of settlements is recognized in each waste layer for second and third loading in the central block due to the accumulation of leachate within the landfill.     

Temporal changes in leachate chemistry of a municipal solid waste landfill cell in Florida,USA

Evaluation of 12 years of landfill leachate chemical data from a lined cell of municipal waste in south Florida, USA shows an overall declining trend in major ion chemistry. The leachate is dominantly Cl, Na, HCO₃ and organic solutes. There are significant short-term variations in concentration that appear to be related to rainfall, rather than fundamental changes to leachate composition. Inorganic parameters related to pH, such as alkalinity, calcium, and magnesium appear to be chemically buffered. Chromium, cobalt, vanadium, zinc, and the metalloid boron display significant short-term co-variance with a decreasing trend. Iron and manganese concentrations increased significantly after capping. Based on the predominance of ammonia, historic methane generation, and increasing trends for iron and manganese after closure, the landfill cell has an anaerobic (reducing) interior environment. The reducing conditions were enhanced by capping and caused the most redox sensitive metals (manganese and iron) to become more mobile.