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PubMed2005

Consequences of raising the height of a landfill in a water-deficient climate.

A large-scale field experiment has been carried out at the Coastal Park landfill which serves the City of Cape Town, South Africa. The landfill is unlined, and the City Council was under pressure from the central Government to cap and close the existing landfill and to establish an extension to the landfill with a lining to prevent the escape of leachate into the ground water. Measuring cells, installed to measure the rate of leachate flow from the landfill had shown that over a period of 9 years, from 1987 to 1995, leachate flow had averaged only 2% of rainfall. It therefore appeared possible, by increasing the moisture absorption capacity of the landfill, i.e., by increasing its height, to stop the leachate flow completely. If this could be achieved, there would be no need for a lining, and the raising would considerably extend the life of the landfill. The paper describes the experiment and its results, including the effects of the raising on leachate flow, settlement, leachate quality and the potential for polluting ground water, and the landfill's water balance.

Ammonia↗
PubMed2002

Poorly humified peat as an adsorbent for metals in wastewater.

Metal adsorption and surface charge determinations were performed previously on well-characterised Sphagnum and Carex peat samples. The aim of this investigation was to determine metal adsorption from complex wastewaters onto these peat samples and compare it to the adsorption onto peat granules, clinoptilolite, glauconite and a flue dust from steel production. A sulphide mine leachate, a landfill leachate and a laundry wastewater were chosen, giving a variation in pH, ionic strength, total organic carbon and concentrations of metals. Metal adsorption was determined in batch and column experiments. The wastewater composition was of great importance for metal removal efficiency, mainly due to the difference in dominating metal species. In the sulphide mine leachate, containing free metal ions, a high metal adsorption was observed onto both peat and inorganic adsorbents. In the landfill leachate the metals formed carbonate and organic complexes and a low metal removal was achieved. Contrary to the leachates, the laundry wastewater contained suspended particles. The high amount of metals removed, 80% of the Cu and 30-60% of the Zn concentration, was probably withdrawn bound to the particle fraction. The highest removal of metal ions was obtained in the sulphide mine leachate with Carex peat, removing 97-99% of the Zn and 85-100% of the Cu content. The Sphagnum peat sample removed 37-77% of the Zn and 80-100% of the Cu content. The differences found between Sphagnum and Carex peat were attributed to the original chemistry of the plant material and the habitat conditions at the time of peat formation. Generally, the combination of glauconite or clinoptilolite with the peat samples in column experiments gave a minor improvement in metal removal.

Adsorption↗
PubMed2002

Bioreactor landfills: experimental and field results.

Bioreactor landfills allow a more active landfill management that recognizes the biological, chemical and physical processes involved in a landfill environment. This paper presents the results of an experimental study carried out to determine the effect of solid waste size, leachate recirculation and nutrient balance on the rate of municipal solid waste (MSW) biodegradation. Higher rates of MSW biodegradation eventually cause a reduction of the contaminant life span of the landfill and decrease in the cost of long term monitoring. The study indicated that the smaller the size of the MSW the faster the biodegradation rate of the waste. In addition, the paper presents the results of leachate recirculation on solid waste biodegradation in a full-scale landfill site, which is located in Nepean, Ontario, Canada. The leachate was recirculated into the landfilled solid waste for 8 years through infiltration lagoons. Similar results to those obtained in the laboratory scale experiments were noted. The average pH of the leachate in the early stages of recirculation was on the acidic range of the pH scale, however, the pH value was in the range of 7-8 after 2 years of leachate recirculation. The concentration of chloride remained fairly constant at about 1000 mg/l during the leachate recirculation period. A decreasing trend of the organic load, measured as biological oxygen demand and chemical oxygen demand, was observed. Recovery of landfill air space was also noted because of the enhanced subsidence and decomposition of the solid waste.

Biodegradation, Environmental↗
PubMed2003

The use of isotopes to identify landfill gas effects on groundwater.

An evaluation of the source of volatile organic compounds in groundwater samples was performed at a landfill in southern California. The 3H (tritium) content of the water in leachate and water from the gas-collection system (condensed water and entrained water droplets) and the delta 13C and 14C content of the inorganic carbon in landfill gas CO2, leachate, and gas-collection system water were used to characterize the dissolved inorganic carbon (DIC) inside the landfill, while the same parameters were monitored in groundwater samples from affected monitoring wells and an unaffected well. Tritium levels from leachate and gas-collection system condensate ranged from approximately 2000 TU to over 4000 TU, orders of magnitude higher than unaffected groundwater. The average 14C content of DIC in the landfill pore-water samples was 121 pMC and the 14C content of unaffected groundwater DIC was 93 pMC, while the 14C content of the dissolved inorganic carbon in groundwater with VOC detections ranged from 105 to 119 pMC. The delta 13C of DIC in pore water was consistently above 0 per thousand and the delta 13C of unaffected groundwater DIC was -20.3 per thousand, while the delta 13C of DIC in affected groundwater samples was increased from -17.3 to -13.2 per thousand. The increases in both delta 13C and 14C in landfill gas-impacted groundwater DIC generally correlated with the number of volatile organic compounds detected and their concentrations. Based on the tritium and DIC 14C levels in leachate and water from the gas-collection system compared to those of unaffected water, significant increases in the tritium content of the water would be expected to accompany VOC detections and increases in delta 13C and 14C caused by landfill water. The results rule out landfill water as the VOC source, leaving landfill gas as the source. The identities and concentrations of the specific VOCs in affected groundwater samples varied among wells as well as between two leachate samples, ruling out the use of a VOC "fingerprint" for leachate or landfill gas to be compared to groundwater VOC concentrations.

Carbon Isotopes↗
PubMed2002

A study of methods to reduce groundwater contamination around the Kimpo landfill in Korea.

Four different methods were studied to reduce the groundwater contamination around the Kimpo landfill in Korea by leakage of a leachate. The hydraulic parameters were measured for this study and then the groundwater flow and contaminant transport systems around the Kimpo landfill were simulated with MODFLOW and MT3D models. Both the method of establishing 5 sets of Radial Collector Well Laterals (RCWLs) within the landfill and a method utilizing the wells for dewatering condensed water brought about a 70% leachate elimination efficiency. Their construction costs were cheap, and the maximum concentrations of chloride and phenol in the leachate effluent were high. Meanwhile, a method establishing an interception wall to the 2nd layer at the cirumference of the landfill and 22 sets of RCWLs within it brought about a 92% leachate elimination efficiency. Its construction cost was expensive, and the maximum concentrations of chloride and phenol in the leachate effluent were low. A method of establishing an interception wall to the 3rd layer and 40 sets of RCWLs brought about a 97% leachate elimination efficiency. Its construction cost was the most expensive, and the maximum concentrations of chloride and phenol were low. Conclusively, a method of establishing 22 sets of RCWLs was evaluated as the most stable and economical option to reduce groundwater contamination concentration below drinking water standard.

Cost-Benefit Analysis↗
PubMed2004

Effect of aeration on the performance of a simulated landfilling reactor stabilizing municipal solid wastes.

In this study, the effects of intermittent aeration on the anaerobic treatment of domestic solid waste and leachate characteristics were investigated in three simulated landfill anaerobic bioreactors. All of the reactors were operated with leachate recirculation and recirculation rate was 300 mL/d. All the reactors were loaded with solid waste having different operational mode. The first reactor was operated with recirculation (control-no aeration). The second reactor was aerated three days in a week during 1 h (Run 1) and the last reactor was aerated one day in a week during 1 h (Run 2). pH, chemical oxygen demand (COD), volatile fatty acids (VFA), ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N) concentrations, total, and methane gas productions in the leachate samples were regularly monitored. 96, 85, and 97% COD and 86, 77, and 93% VFA removals were obtained, in the leachate samples of the control, R1 and R2 reactors, respectively, after 79 days of anaerobic incubation. The TN, TP and NH4-N concentrations in MSW reduced to 4300, 1100, and 160 mg/g from 11,100, 2450, and 630 mg/g in R1 reactor by day 79. The values of pH were 6.98, 6.76, and 7.98, respectively, after anaerobic incubation, respectively in the aforementioned reactors. It was observed that the aeration decreased the methane percentage and the quantity in the simulated bioreactor. The maximum cumulative methane gas production was recorded as 11.2, 0.9, and 3.6 L in control, R1 and R2 reactors, respectively, at the end of 79 days. A BOD5/COD ratio of 0.23 achieved in the R2 reactor indicated the better MSW stabilization resulting in a high rate than that of R1 and control reactors. It was observed that the aerated reactor one day in a week during one hour (R2) reduced the COD and VFA concentrations in leachate samples. The aerated reactor three days in a week during 1 h (R1) reduced the waste quantity, the organic content of the solid waste. The final leachate quantities of aerated runs were lower than that of control reactor operated under strictly anaerobic conditions.

Bacteria, Anaerobic↗
PubMedDate not supplied

Nitrate leaching beneath a containerized nursery crop receiving trickle or overhead irrigation.

Container production of nursery crops is intensive and a potential source of nitrogen release to the environment. This study was conducted to determine if trickle irrigation could be used by container nursery producers as an alternative to standard overhead irrigation to reduce nitrogen release into the environment. The effect of overhead irrigation and trickle irrigation on leachate nitrate N concentration, flow-weighted nitrate N concentration, leachate volume, and plant growth was investigated using containerized rhododendron (Rhododendron catawbiense Michx. 'Album') supplied with a controlled-release fertilizer and grown outdoors on top of soil-monolith lysimeters. Leachate was collected over two growing seasons and overwinter periods, and natural precipitation was allowed as a component of the system. Precipitation accounted for 69% of the water entering the overhead-irrigated system and 80% of the water entering the trickle-irrigated system. Leachate from fertilized plants exceeded the USEPA limit of 10 mg L(-1) at several times and reached a maximum of 26 mg L(-1) with trickle irrigation. Average annual loss of nitrate N in leachate for fertilized treatments was 51.8 and 60.5 kg ha(-1) for the overhead and trickle treatments, respectively. Average annual flow-weighted concentration of nitrate N in leachate of fertilized plants was 7.2 mg L(-1) for overhead irrigation and 12.7 mg L(-1) for trickle irrigation. Trickle irrigation did not reduce the amount of nitrate N leached from nursery containers when compared with overhead irrigation because precipitation nullified the potential benefits of reduced leaching fractions and irrigation inputs provided under trickle irrigation.

Agriculture↗
PubMedDate not supplied

Soil testing to predict phosphorus leaching.

Subsurface pathways can play an important role in agricultural phosphorus (P) losses that can decrease surface water quality. This study evaluated agronomic and environmental soil tests for predicting P losses in water leaching from undisturbed soils. Intact soil columns were collected for five soil types that a wide range in soil test P. The columns were leached with deionized water, the leachate analyzed for dissolved reactive phosphorus (DRP), and the soils analyzed for water-soluble phosphorus (WSP), 0.01 M CaCl2 P (CaCl2-P), iron-strip phosphorus (FeO-P), and Mehlich-1 and Mehlich-3 extractable P, Al, and Fe. The Mehlich-3 P saturation ratio (M3-PSR) was calculated as the molar ratio of Mehlich-3 extractable P/[Al + Fe]. Leachate DRP was frequently above concentrations associated with eutrophication. For the relationship between DRP in leachate and all of the soil tests used, a change point was determined, below which leachate DRP increased slowly per unit increase in soil test P, and above which leachate DRP increased rapidly. Environmental soil tests (WSP, CaCl2-P, and FeO-P) were slightly better at predicting leachate DRP than agronomic soil tests (Mehlich-1 P, Mehlich-3 P, and the M3-PSR), although the M3-PSR was as good as the environmental soil tests if two outliers were omitted. Our results support the development of Mehlich-3 P and M3-PSR categories for profitable agriculture and environmental protection; however, to most accurately characterize the risk of P loss from soil to water by leaching, soil P testing must be fully integrated with other site properties and P management practices.

Agriculture↗
PubMedDate not supplied

Leaching from organic matter-rich soils by rain of different qualities: I. Concentrations.

Soil monoliths from an area exposed to acid precipitation and from an unpolluted area were used in a lysimeter experiment to study effects of different rain qualities on the chemical composition of the leachate from shallow soils rich in organic matter. The vegetation was either dominated by moorgrass [Molinia caerulea (L.) Moench] or heather [Calluna vulgaris (L.) Hull]. The lysimeters received either "acid rain" (pH 4.3) or "normal rain" (pH 5.3). High concentrations of dissolved organic carbon (DOC) were characteristic of the leachate. The different "rain" qualities had no significant influence on the DOC concentration. More DOC was, however, leached from lysimeters with heather vegetation. Roughly 50% of the aluminum (Al) was in complex with organic material and the Al charge was calculated to be between +1.4 and +2.0. Sulfate (SO4(2-)) was the only component that was significantly influenced by the treatment, as more was leached from lysimeters receiving "acid rain." Sulfate was poorly correlated with pH, suggesting that reduced SO4(2-) input would not necessarily lead to reduced acidity. Differences in the pH of the leachate due to the treatments were less than 0.15 pH units. Nitrate (NO3-) was only leached in very low concentrations and of little consequence for the leachate acidity. Some observations do, however, suggest that NO3- may contribute to acidification in episodes with high precipitation. High concentrations of Cl- in the leachate and a significant positive correlation between Cl-, H+, and base cations indicate that sea salt episodes may be important for soil acidification and acidity of the leachate.

Acid Rain↗
PubMed1992

Toxicity of construction materials in the marine environment: a comparison of chromated-copper-arsenate-treated wood and recycled plastic.

Previous studies have demonstrated leaching from chromated-copper-arsenate (CCA)-treated wood, which is used in pilings and bulkheads, and resulting toxicity to various estuarine organisms. The current study compared effects of leachates from CCA-treated wood with those of recycled plastic "lumber," a possible alternative construction material. Limb regeneration in fiddler crabs, while depressed in leachates from CCA wood, was accelerated in three formulations of recycled plastics. The acceleration was reduced in subsequent trials with the same pieces of plastic. Using a sea urchin fertilization test, no effects were seen in 1- and 3-day leachates from the plastics. However, CCA wood reduced fertilization by 90%, and totally inhibited larval development of those that did fertilize. A smaller piece of wood, one-tenth the size (0.4 cm2), did not have a significant effect on fertilization or development. With 1-3 weeks of leaching, significant reductions in fertilization were seen in sea urchin gametes exposed to one plastic formulation and no fertilization was seen in leachates from the small piece of CCA wood. Two formulations enriched to 30% polystyrene (PS) had no significant effect on fertilization, but did reduce larval growth. When the same pieces of plastic and wood were used for a second set of experiments, all three formulations of plastic, as well as the small piece of wood, inhibited fertilization significantly, and one of the 30% PS formulations and the wood caused reduced larval growth. In another assay, snails and an alga were exposed to plastics for two months with no observed effect; the CCA leachates caused 100% snail mortality within one week and chlorosis of the alga.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Heavy metal leaching from mine tailings as affected by organic amendments.

A column experiment was conducted to investigate Zn, Cd, and Pb leaching from mine tailings as affected by the addition of organic amendments. Composted yard waste, composted cattle manure, and cattle manure aged for one month increased heavy metal leaching from mine tailings when compared to an unamended control. Aged cattle manure and composted cattle manure significantly increased Zn concentration in the leachate. The maximum Zn concentration in leachate from the manure-amended treatments was as high as 3.7 mg/L, whereas Zn concentrations from the control were less than 0.7 mg/L. All organic amendments increased Cd leachate concentrations. The presence of aged cattle manure greatly increased Pb concentrations in the leachate from less than 10 microg/L for the control treatment to higher than 60 microg/L. Lead concentration in leachate was positively correlated with inorganic carbon, total organic carbon, total carbon and bicarbonate. Although organic amendments increased Zn, Cd, and Pb leaching when compared with the control treatment, Zn concentrations were lower than the 5 mg/L secondary drinking water standard, and Pb concentrations were only minimally higher than the 15 microg/L drinking water standard. Cadmium concentrations from manure treatments exceeded the 5 microg/L drinking water standard but only during the first 15 days. Organic amendments may encourage establishment of vegetation in mining areas that may minimize heavy metal contamination through runoff and erosion. However, increased risk due to heavy metal leaching in the presence of organic amendments should be carefully considered.

Metals, Heavy↗
PubMed2004

Biodegradation efficiency of functionally important populations selected for bioaugmentation in phenol- and oil-polluted area.

Denaturing gradient gel electrophoresis of amplified fragments of genes coding for 16S rRNA and for the largest subunit of multicomponent phenol hydroxylase (LmPH) was used to monitor the behaviour and relative abundance of mixed phenol-degrading bacterial populations (Pseudomonas mendocina PC1, P. fluorescens strains PC18, PC20 and PC24) during degradation of phenolic compounds in phenolic leachate- and oil-amended microcosms. The analysis indicated that specific bacterial populations were selected in each microcosm. The naphthalene-degrading strain PC20 was the dominant degrader in oil-amended microcosms and strain PC1 in phenolic leachate microcosms. Strain PC20 was not detectable after cultivation in phenolic leachate microcosms. Mixed bacterial populations in oil-amended microcosms aggregated and formed clumps, whereas the same bacteria had a planktonic mode of growth in phenolic leachate microcosms. Colony hybridisation data with catabolic gene specific probes indicated that, in leachate microcosms, the relative proportions of bacteria having meta (PC1) and ortho (PC24) pathways for degradation of phenol and p-cresol changed alternately. The shifts in the composition of mixed population indicated that different pathways of metabolism of aromatic compounds dominated and that this process is an optimised response to the contaminants present in microcosms.

Biodegradation, Environmental↗
PubMed2001

Solidification/stabilization of electric arc furnace dust using coal fly ash. Analysis of the stabilization process.

In this paper, the stabilization of electric arc furnace (EAF) dust containing hazardous metals such as Pb, Cd, Cr or Zn is described. The treatment involves a waste solidification/stabilization (S/S) process, using coal fly ash as the fundamental raw material and main binder. The article also contains a brief review of the most important recent publications related to the use of fly ash as S/S agents. The efficacy of the process has been evaluated mainly through leaching tests on the solidified products and compliance with some imposed leachate limits. The concentration of metals leaching from the S/S products was strongly leachate pH dependent; thus, the final pH of the leachate is the most important variable in reaching the limits and, therefore, in meeting the stabilization goals. In this study, the dependence relationship between the leachate pH and the concentrations of metals in the leachate are analyzed; in some cases, this allows us to estimate the speciation of contaminants in the S/S solids and to understand the mechanism responsible for reduced leachability of heavy metals from solidified wastes.

Coal↗
PubMed2002

Solidification/stabilisation of arsenic bearing fly ash from the metallurgical industry. Immobilisation mechanism of arsenic.

When a fly ash waste material from a copper refining process containing large amounts of As2O3 is solidified using cement and lime, the arsenic concentration in the leachate can be lowered to ca. 5 mg/l in a saturated solution of Ca(OH)2. It is shown that the decrease of the concentration in the leachate, mainly of As(III), is due to the formation of insoluble CaHAsO3 in the leachate in the presence of Ca(OH)2. This method is compared with a method whereby use is made of oxidation of the waste before solidification to oxidise As(III) to As(V) using H2O2. The arsenic concentration in the leachate of the extraction test of an oxidised S/S sample was lowered to ca. 0.5 mg/l, a factor of 10 below the one for a non-oxidised sample. It is shown that the decrease of the concentration in the leachate mainly of As(V) is due to the formation of insoluble Ca3(AsO4)2 in the presence of Ca(OH)2. Extensive use was made of the speciation program MINTEQA2, to clarify the immobilisation of arsenic.

Arsenic↗
PubMed2003

Environmental impact of highway construction and repair materials on surface and ground waters. Case study: crumb rubber asphalt concrete.

The practice of incorporating certain waste products into highway construction and repair materials (CRMs) has become more popular. These practices have prompted the National Academy of Science, National Cooperative Highway Research Program (NCHRP) to research the possible impacts of these CRMs on the quality of surface and ground waters. State department of transportations (DOTs) are currently experimenting with use of ground tire rubber ( crumb rubber) in bituminous construction and as a crack sealer. Crumb rubber asphalt concrete (CR-AC) leachates contain a mixture of organic and metallic contaminants. Benzothiazole and 2(3H)-benzothiazolone (organic compounds used in tire rubber manufacturing) and the metals mercury and aluminum were leached in potentially harmful concentrations (exceeding toxic concentrations for aquatic toxicity tests). CR-AC leachate exhibited moderate to high toxicity for algae ( Selenastrum capriconutum) and moderate toxicity for water fleas ( Daphnia magna). Benzothiazole was readily removed from CR-AC leachate by the environmental processes of soil sorption, volatilization, and biodegradation. Metals, which do not volatilize or photochemically or biologically degrade, were removed from the leachate by soil sorption. Contaminants from CR-AC leachates are thus degraded or retarded in their transport through nearby soils and ground waters.

Animals↗
PubMed2003

Evaluation of bottom ash and composted manure blends as a soil amendment material.

The long-term goal of this project was to find alternative uses for bottom ash (BA) and composted dairy manure (CM), by-products of coal combustion and livestock production, respectively. The study discussed in this paper focused on potential water quality impacts associated with using blended BA and CM as a soil amendment. The constituents of BA and CM include heavy metals and other chemicals that, while essential nutrients for plant growth, also pose a potential threat to water quality. Four blends (BA:CM, v/v) namely, B1 (100%:0%), B2 (70%:30%), B3 (50%:50%) and B4 (0%:100%), were subjected to flow-through water table management and two blends, B2 (70%:30%) and B3 (50%:50%), were subjected to constant head water table management using de-ionized water. Leachate and standing water from saturated and flooded blends of BA and CM were examined for total solids (TS), volatile solids (VS), COD, pH, total Kjeldahl nitrogen (TKN), NO(3)-N, total P, total K as well as selected metals over a 5 and 7 week period for flow-through and constant head watertables, respectively. The results showed that higher CM content resulted in higher TS, VS, TKN, P and K concentrations in the leachate and standing water. Concentrations of these constituents were higher in leachate than in the standing water. Even though, marked reductions of most chemicals in the leachate and standing water were realized within one to three weeks, initially high concentrations of chemicals in leachate and standing water from these particular blends made them unsuitable as soil amendment material. Based upon these results, it was concluded that additional column studies of BA and CM blends with reduced CM content (5%, 10% and 20%) should be performed to further assess the feasibility of BA and CM blends as an environmentally safe soil amendment material.

Carbon↗
PubMed2001

Factors controlling alkylbenzene sorption to municipal solid waste.

The sorption of toluene and o-xylene to individual municipal solid waste (MSW) constituents [office paper, newsprint, model food and yard waste, high density polyethylene, and poly(vinyl chloride) (PVC)] was evaluated. Effects of sorbent decomposition and solvent composition on alkylbenzene sorption were studied by evaluating biodegradable sorbents in both fresh and anaerobically decomposed form and by complementing single-solute isotherm tests with experiments conducted in acidogenic and methanogenic leachate. Alkylbenzene sorption to plastics was greaterthan to biopolymer composites, and differences in sorbate/sorbent solubility parameter compatibility explained this observation. Alkylbenzene sorption to biopolymer composites yielded linear isotherms, and sorption capacities [log(Koc/Kow)] decreased linearly with increasing sorbent polarity as expressed by the O-alkyl/alkyl ratio. Leachate composition had little effect on alkylbenzene sorption with one exception; volatile fatty acids in acidogenic leachate appeared to convert PVC from a glassy to a rubbery polymer. The results of this study showed that sorbent organic matter affinity for hydrophobic organic contaminants (HOCs) increases with increasing extent of MSW decomposition because of the recalcitrance of plastics and the preferential degradation of polar biopolymers. Furthermore, the plasticizing effect of volatile fatty acids in acidogenic leachate may enhance the bioavailability of HOCs sorbed to glassy organic matter in MSW or in soils contaminated with acidogenic leachate.

Adsorption↗
PubMed2004

TCLP underestimates leaching of arsenic from solid residuals under landfill conditions.

Recent revision of the arsenic in drinking water standard will cause many utilities to implement removal technologies. Most of the affected utilities are expected to use adsorption onto solid media for arsenic removal. The arsenic-bearing solid residuals (ABSR) from adsorption processes are to be disposed of in nonhazardous landfills. The Toxicity Characteristic Leaching Procedure (TCLP) tests whether a waste is hazardous or nonhazardous; most solid residuals pass the TCLP. However, the TCLP poorly simulates the alkaline pH, low redox potential, biological activity, long retention time, and organic composition of mature landfills. These same conditions are likely to favor mobilization of arsenic from metal oxide sorbents. This study quantifies leaching of arsenic from Activated Alumina (AA) and Granular Ferric Hydroxide (GFH), two sorbents expected to be widely used for arsenic removal. The sorbents were subjected to the TCLP, the Waste Extraction Test (WET), an actual landfill leachate, and two synthetic leachate solutions. Up to tenfold greater arsenic concentration is extracted by an actual landfill leachate than by the TCLP. Equilibrium leachate concentrations are not achieved within 18 h (the TCLP duration) and an N2 headspace and end-over-end tumbling increase the rate of arsenic mobilization. However, tests with actual landfill leachate indicate the WET may also underestimate arsenic mobilization in landfills.

Adsorption↗