Landfill Leachate Contamination Research Articles

Microplastics and per- and polyfluoroalkyl substances (PFAS) in landfill-wastewater treatment systems: A field study

Landfills and wastewater treatment plants (WWTP) are point sources for many emerging contaminants, including microplastics and per- and polyfluoroalkyl substances (PFAS). Previous studies have estimated the abundance and transport of microplastics and PFAS separately in landfills and WWTPs. In addition, previous studies typically report concentrations of microplastics as particle count/L or count/g sediment, which do not provide the information needed to calculate mass balances. We measured microplastics and PFAS in four landfill-WWTP systems in Illinois, USA, and quantified mass of both contaminants in landfill leachate, WWTP influent, effluent, and biosolids. Microplastic concentrations in WWTP influent were similar in magnitude to landfill leachates, in the order of 102 μg plastic/L (parts-per-billion). In contrast, PFAS concentrations were higher in leachates (parts-per-billion range) than WWTP influent (parts-per-trillion range). After treatment, both contaminants had lower concentrations in WWTP effluent, although were abundant in biosolids. We concluded that WWTPs reduce PFAS and microplastics, lowering concentrations in the effluent that is discharged to nearby surface waters. However, partitioning of both contaminants to biosolids may reintroduce them as pollutants when biosolids are landfilled or used as fertilizer.

Revolutionizing Waste Management: Solidification of Landfill Leachates Using Alkali-Activated Slag

AbstractLandfill leachate is a highly hazardous effluent characterized by a high concentration of recalcitrant pollutants, presenting a significant environmental challenge. This study investigated the solidification of landfill leachate contaminants using sodium hydroxide-activated Granulated Blast Furnace Slag (GBFS). The stability of the resulting geopolymer was evaluated through unconfined compressive strength and leaching tests. Optimal curing conditions were identified as 7 days at a sodium hydroxide concentration of 12 M, achieving an unconfined compressive strength of 45.738 MPa at a liquid-to-solid ratio of 15%. A linear relationship was observed between the liquid-to-solid ratio and flow workability, with maximum flow workability evidenced by an average diameter of 242 mm at a liquid-to-solid ratio of 0.25. However, a minimum liquid-to-solid ratio of 0.15 was necessary to obtain a workable mortar. The produced geopolymers were characterized using X-ray Fluorescence (XRF) for mineralogical analysis, Scanning Electron Microscopy (SEM) for morphological examination, and the Toxicity Characteristic Leaching Procedure (TCLP) for leaching tests. The findings demonstrated the successful solidification of landfill leachate using GBFS geopolymer. The leachability tests revealed that the geopolymer did not release metals in concentrations exceeding the allowable limits set by the United States Environmental Protection Agency (USEPA), indicating effective encapsulation of the pollutants within the geopolymer matrix. Furthermore, the resultant geopolymer brick is eco-sustainable and can be classified as a green construction material.

Advanced leachate treatment at Mascara landfill (Algeria): A hybrid pilot approach with activated sludge and ferric chloride

This study investigates a hybrid treatment approach, that combines a Sequencing Batch Reactor (SBR) with a coagulation-flocculation process, to reduce the contaminants in Landfill Leachate (LL), targeting Chemical Oxygen Demand (COD), Turbidity, and Total Suspended Solids (TSS). The experimental set-up incorporated a batch reactor at room temperature and a pH between 7.7 and 8.7, with an Arduino monitoring system for heightened precision. The SBR was operated continuously over a 24-hour cycle, with a Hydraulic Retention Time (HRT) set at 5 days and variable sludge retention times (SRT) of 5, 10, and 15 days. The Aluminum sulfate (Al2 (SO4)3), Ferric Chloride (FeCl3), and Lime (CaO) were assessed for the coagulation-flocculation process. The results indicate a promising removal efficiency of 40 % for COD, 31 % for turbidity, and 47 % for TSS using the SBR process. FeCl3 showed higher findings, achieving removal yields of 87 % for COD and 86 % for turbidity, at an optimized dose of 10 g/L and pH 5.5. Furthermore, adding 0.25 g/L of CaO significantly improved the removal efficiency to 94.14 % for COD, 98.22 % for turbidity and 99.78 % of the TSS. Therefore, this study's results underline the effectiveness of combining SBR with coagulation-flocculation, particularly using FeCl3 and CaO, in treating landfill leachate.

Aging behavior and leaching characteristics of microfibers in landfill leachate: Important role of surface mesh structure

Mesh-structured films formed by the post-processing of microfibers improves their permeability and dexterity, such as disposable masks. However, the aging behavior and potential risks of mesh-structured microfibers (MS-MFs) in landfill leachate remain poorly understood. Herein, the aging behavior and mechanisms of MS-MFs and ordinary polypropylene-films (PP-films) microplastics, as well as their leaching concerning dissolved organic matter (DOM) in landfill leachate were investigated. Results revealed that MS-MFs underwent more significant physicochemical changes than PP-films during the aging process in landfill leachate, due to their rich porous habitats. An important factor in the photoaging of MS-MFs was related to reactive oxygen species produced by DOM, and this process was promoted by photoelectrons under UV irradiation. Compared with PP-films, MS-MFs released more DOM and nano-plastics fragments into landfill leachate, altering the composition and molecular weight of DOM. Aged MS-MFs-DOM generated new components, and humus-like substances produced by photochemistry showed the largest increase. Correlation analysis revealed that leached DOM was positively correlated with oxygen-containing groups accumulated in aged MS-MFs. Overall, MS-MFs will bring higher environmental risks and become a new long-term source of DOM contaminants in landfill leachate. This study provides new insights into the impact of novel microfibers on landfill leachate carbon dynamics.

Laboratory Experiments on Remediation of Landfill Leachate Contamination with Permeable Reactive Barriers (PRBs) of Reactive Media Derived from Waste

Groundwater at landfills is often contaminated with heavy metals. Permeable reactive barrier (PRB), a potential in-situ treatment system, was investigated in this study, using 'composite reactive media' (COM), primarily composed of waste materials, to remediate heavy metals in groundwater. The COM consisted of 40% Brick and Mortar Waste (BMW), 40% Biochar (BC), 10% Granular Activated Carbon (GAC), and 10% Zeolite, based on volume. In an up-flow column, the average removal efficiencies of Fe, Pb, Cu, As, Mn, Zn, and Cd were 70.9±2.7, 80.9±3.2, 72.2±1 .6, 76.3±2.5, 81.6±6.3, 88.0±2.0, and 67.3±4.6%, respectively. In a bench-scale COM-filled PRB (0.85 x 0.25 x 0.3 m), the average removal efficiencies of the same species were 71.4±1.3, 75.4±4.9, 67.4±4.3, 72.9±1.3, 83.6±7.6, 89.8±7.4, and 80.9±7.1%, respectively. Adsorption associated with fixation, and ion exchange could be the main treatment mechanisms. COM also has potential as a filtration medium in other treatment unit processes and to treat some other types of wastewater than landfill-leachate. Further, this use of COM could alleviate the burden of disposing of BMW waste, thereby addressing a significant issue in waste management. As the identification of potential failure points in reactive media is crucial, field-scale experiments are suggested to be conducted for further investigation.

Nitrogen Removal from Landfill Leachate Using Biochar Derived from Wheat Straw.

Landfill leachate (LLCH) disposal poses challenges due to high pollutant concentrations. This study investigates the use of biochar (BC) derived from wheat straw for nitrogen content reduction. Laboratory experiments evaluated BC's adsorption capacity (qm) for nitrogen removal from ammonium chloride solution (NH4Cl) and LLCH, along with testing isotherm models. The results demonstrated that BC was more efficient (95.08%) than commercial activated carbon AC (93.11%), the blank, in adsorbing nitrogen from NH4Cl. This superior performance of BC may be attributed to its higher carbon content (57.74%) observed through elemental analysis. Lower results for BC/LLCH may be due to LLCH's complex chemical matrix. The Langmuir isotherm model best described BC/NH4Cl adsorption (qm = 0.5738 mg/g). The AC/NH4Cl data also fitted into the Langmuir (R2 ˃ 0.9) with a qm of 0.9469 mg/g, and 26.667 mg/g (R2 ˂ 0.9) was obtained for BC/LLCH; the BC/LLCH also gave higher qm (R2 ˃ 0.9) using the Jovanovich model (which also follows Langmuir's assumptions). The mean energy of the adsorption values estimated for the AC/NH4Cl, BC/NH4Cl, and BC/LLCH processes were 353.55, 353.55, and 223.61 kJ/mol, respectively, suggesting that they are all chemisorption processes and ion exchange influenced their adsorption processes. The Freundlich constant (1/n) value suggests average adsorption for BC/LLCH. The BC/LLCH data followed the Harkins-Jura model (R2: 0.9992), suggesting multilayered adsorption (or mesopore filling). In conclusion, biochar derived from wheat straw shows promising potential for landfill leachate remediation, offering efficient nitrogen removal capabilities and demonstrating compatibility with various adsorption models. This research also lays the groundwork for further exploration of other biochar-based materials in addressing environmental challenges associated with landfill leachate contamination.

Electro-catalytic ozonation of contaminants in landfill leachate: Optimization by BBD, economic evaluation, mechanism, and reaction pathway

An electro-catalytic ozonation process with ZnO nano-granules as a catalyst (CFR-EC/O3-UV@ZnO process) was developed to treat raw landfill leachate. LC-MS analysis was applied to determine organic compounds. After CFR-EC/O3-UV@ZnO process, COD, TOC, BOD5, NH4+-N, P-PO4−3, color, and turbidity were reduced to 90.9%, 89.4%, 89.1%, 89.5%, 87.7%, 99.1%, and 99.7%, respectively under the optimum conditions of 10 g.hr−1 O3 dosage, pH 11.0, and 0.006 L.min−1 flowrate. At the same conditions removal efficiencies of heavy metals (HMs): Cr6+, Pb2+, As3+, Mg2+, B3+, Mn3+, Ni2+, Ba2+, Hg2+, Co2+, Fe2+, and Li+ were obtained 90%, 84.7%, 90%, 99%, 83.7%, 95%, 20%, 75%, 91%, 90%, 78% and 60%, respectively. In spite of high COD and BOD5 removal efficiencies, the process could not remove two organic substances including diphenylamine and 2,2,4-trimethyl-1,3-pentanediol. A high R2 value of 0.99 demonstrated the accuracy of the selected model. Economic evaluation depicted that the current process cost 0.95 $.m−3. Finally, this process is suggested for the treatment of landfill leachate with relatively high efficiency.

Microplastics as emergent contaminants in landfill leachate: Source, potential impact and remediation technologies

A significant amount of plastic waste is generated each year on a global scale, in which the maximum quantity of plastic waste is typically dumped in landfills in various parts of the world. Moreover, dumping plastic waste in landfills cannot address the issue of proper disposal; it simply delays the process. Exploiting waste resources entails environmental hazards because plastic wastes buried in landfills gradually break down into Microplastics (MPs) due to physical, chemical, and biological effects. The possibility of landfill leachate as a source of MPs in the environment has not received much attention. Without systematic treatment, MPs in leachate increase the risk to human health and environmental health since they contain dangerous and toxic pollutants and antibiotic resistance genes transmitted by leachate vectors. Due to their severe environmental risks, MPs are now widely recognized as emerging pollutants. Therefore, the composition of MPs in landfill leachate and the interaction of MPs with other hazardous contaminants are summarised in this review. The available potential mitigation or treatment methods of MPs in landfill leachate as of now, along with the drawbacks and challenges of the present leachate treatment for eliminating MPs, are described in this review. Since it is unclear how MPs will be removed from the current leachate facilities, it is crucial to develop innovative treatment facilities as quickly as possible. Finally, the areas that require more research to provide complete solutions to the persistent problem of plastic debris are discussed.

Simultaneous removal of organic and nitrogenous compounds in mature landfill leachate by a hybrid electro-oxidation-dialysis (EOD) system

ABSTRACT Electrochemical process has been widely applied to eliminate recalcitrant contaminants (i.e., organic and nitrogenous compounds) in landfill leachate. This study aimed to evaluate the performance of a hybrid electro-oxidation-dialysis (EOD) system to minimize organic and nitrogenous compounds through a synergistic process of electrochemical oxidation (EO) and electrodialysis (ED) as well as the dissolved organic matter was characterized in terms of fluorescent component and molecular weight distribution. The EOD was carried out using boron-doped diamond (BDD) and Pt alternately. The results have shown that pH adjustment to acidic conditions is beneficial to EO. At optimal pH (pH 4), BDD-based EO is superior to removing COD and NH 4 + up to around 56% and 64%, respectively. During EOD process, the lower current density at 20.83 mA cm−2 is preferred for the recovery of nitrogenous ions (i.e. NH 4 + and NO 3 – ), especially for BDD-EOD. In addition, the dominant humic acid-like (HAL) and soluble microbial products-like (SMPL) substances in the mature leachate are mostly degraded to smaller molecules from 105 Da to 103 Da in both EOD processes. Overall, BDD-EOD favours indirect oxidation and has a higher energy consumption efficiency than Pt-EOD induced by direct oxidation for simultaneous removal of organic and nitrogenous compounds. BDD-EOD requires a lower total operation cost of around $2.33/m3 compared to Pt-EOD. It is concluded that the hybrid BDD-EOD process is technically feasible as a powerful pre-treatment approach to mature landfill leachate for refractory organics degradation and nitrogenous nutrients recovery.

Application of electro-Fenton and photoelectro-Fenton processes for the degradation of contaminants in landfill leachate

Worldwide, most solid waste ends its life in landfill sites, which have a significant environmental impact in several respects. In particular, rainfall over landfill sites results in the production of an aqueous leachate containing compounds having low biodegradability, high toxicity, and a high organic load. For this reason, this study aims to investigate the applicability of electro-Fenton (EF) and photoelectro-Fenton (PEF) processes as alternative for treating a local landfill effluent with high organic content (chemical oxygen demand (COD) = 2684.7 mg-O2 L −1) in a continuous-flow reactor (using, for first time, this kind of system with higher electrodes area of 35 cm2) using boron-doped diamond anode (Nb/BDD) and a carbon felt cathode (FC) electrodes. The effects of current density j (30, 60 and 90 mA cm−2) and UV radiation wavelength (UVA and UVC) were studied to evaluate the treatment efficiency as well as the energy consumption. Results clearly showed that, the best efficiencies removing organic matter, in terms of COD, were about 66%, 68% and 89% with an energy consumption of only 19.41, 17.61 and 17.59 kWh kg COD−1 for EF, PEF-UVA and PEF-UVC respectively, at 90 mA cm−2 after 4 h of operation. The treatment of this kind of effluent produced organic and inorganic by-products, the acetic and formic acids as well as NO2−, NO3−, and NH4+, being assessed their concentrations.

Removal efficiency of organic contaminants in landfill leachate contaminated groundwater under oxygen micro–nano bubble aeration

Oxygen micro–nano bubble (MNB) aeration was used to treat landfill leachate contaminated groundwater.

Study of soil properties affected by leachate – A case study at Urali-Devachi, Pune, India

Landfill leachate is created via decomposition of landfill waste transported by water percolation through the soil layers. If the landfill sites are not designed properly then the leachate simply passes through the soil layers. This may create an adverse effect on the engineering properties of soil, as well as on the chemical properties viz. adsorption and retention of heavy metals. In the present study, an experimental work was carried out to examine the effects of landfill leachate contamination on the soil properties viz. physiochemical and geotechnical of an active Municipal Solid Waste (MSW) dumping site located near Pune city, India. The soil samples were collected from three different locations (at 150 m spacing) and leachate was collected from the treatment plant, located in the premises of the dumping site. The test result shows that the leachate containing the highest concentration of metals, Biochemical Oxygen Demand (BOD), and Chemical Oxygen Demand (COD). The soil sample in close proximity to the MSW dumpsite is most contaminated as compared to the furthermost soil samples, because of the high contents of organic pollutants and heavy metals. The present study clearly indicates that if the leachate is permitted to drain straightway into the surface water or infiltrates in to the groundwater it can cause adverse effect on human health and environment.

Identifying and Monitoring the Landfill Leachate Contamination in Groundwater with SEC-DAD-FLD-OCD and a Portable Fluorescence Spectrometer

Landfill leachate contains high concentrations of dissolved organic matter (DOM), which might leak into the groundwater as a contaminant plume. In this study, 6 landfill leachates, 11 landfill solid waste and soil samples, and 102 groundwater samples around 24 landfills were collected, in order to identify the suitable tracers and develop a convenient technique for monitoring groundwater contamination from landfill leachate. Characterized by the size exclusion chromatography-diode array detector-fluorescence detector-organic carbon detector (SEC-DAD-FLD-OCD) chromatograms, DOM in landfill leachate consisted of a characteristic humic-like fluorophore with triple-excitation peaks at Ex ∼ 250, 310, and 365 nm/Em ∼ 460 nm (HS-Em460-Ex3). With an apparent MW of 1.4–2.5 kDa, this unique HS-Em460-Ex3 fluorophore was refractory to biodegradation and possibly originated from the biotransformation of dyes in municipal solid wastes. Via principal factor analysis, groundwater samples were clustered into two groups mainly by the PC1 dimension, which mainly represented the variances in DOM concentration. The samples in Group II all showed the characteristic HS-Em460-Ex3 fluorophore, which could serve as an intrinsic fluorescence tracer of landfill leachate contamination. Checked by SEC-FLD analysis, the humic-like fluorescence threshold value was proposed as 50 QSU to indicate the pollution risks of groundwater around landfills, and the portable UV-LED fluorescence spectrometer provides an on-site tool for fast screening groundwater contamination from landfill leachate. The SEC-FLD fingerprint and the portable fluorescence spectrometer were developed for identifying and fast screening groundwater contamination from landfill leachate.

Enhanced degradation of old landfill leachate in heterogeneous electro–Fenton catalyzed using Fe3O4 nano–particles encapsulated by metal organic frameworks

Organic contaminants in old landfill leachate could cause large harm to human and environment without a proper treatment. In the present study, Fe3O4 nano–particles encapsulated by metal organic frameworks (Fe3O4NPs@MOF) was prepared, characterized and then applied to construct heterogeneous electro–Fenton (hetero–EF) process treating old landfill leachate. Increasing catalyst dosage, current density, plate distance and lower pH promoted the hetero–EF performance, COD removal efficiency could reach 66.67 ± 4.36% with catalyst dosage of 0.75 g/L, current density of 15 mA/cm2, plate distance of 1.5 cm and pH of 3. •OH played a more remarkable effect on organic contaminants degradation and contributed 76% of the COD removal. The MOF shell might protect Fe3O4 NPs in the core from reacting with acid solution, and mesoporous pore allowed e−, H+ and H2O2 to cross MOF shell and react with Fe3O4 NPs. Heterocycles, phenols and esters in old landfill leachate were dramatically degraded by hetero–EF, and the relative abundance of low molecular weight organics (<1 kDa) increased from 62.8% to 71.56% with BOD5/COD increasement from 0.025 to 0.39. It is suggested that heterogeneous electro–Fenton using Fe3O4NPs@MOF as catalyst would be an effective method to remove organic contaminants in old landfill leachate.

Analysis of the possibility of conducting a comprehensive assessment of landfill leachate contamination using physicochemical indicators and toxicity test

The inevitable consequence of the operation of landfills is the emission of leachate, which is considered to be one of the main polluters of the ground and water environment. The leachate contains soluble organic compounds, inorganic contaminants, suspended solids, heavy metals and dangerous substances. The selection of the leachate disposal method requires a comprehensive assessment of its properties. Therefore, the physicochemical parameters and toxicity tests were chosen for a comprehensive assessment of the properties of leachate. Four municipal waste landfills (operational and non-operational) were selected for the study, for which multidimensional statistical analyses were carried out. The study was conducted between the period of April 2018 and December 2019. The comprehensive assessment showed that pollutants in leachate from the analyzed landfills remained at a level which did not allow them to be discharged to water or soil. The presence of substances particularly harmful to the aquatic environment (e.g AN, chromium, copper) may hinder their treatment together with household sewage, as it involves obtaining a permit required under laws. Toxicity of leachate may also be a problem, as it may persist after the treatment process is completed. The values of pH, EC and the concentrations of ON, TDS, TSS, chloride, iron and manganese had the strongest influence on the properties of leachate from all landfills. For operational landfills, these were also calcium concentrations, for non-operational ones COD, TU and the concentrations of TKN, AN, TS, sodium, potassium and magnesium. The mentioned parameters also showed strong correlation with other physicochemical properties of the leachate, which indicate their suitability for the monitoring of leachate and the aquatic environment in the vicinity of municipal waste landfills.

Potential Environmental and Human Health Risks Caused by Antibiotic-Resistant Bacteria (ARB), Antibiotic Resistance Genes (ARGs) and Emerging Contaminants (ECs) from Municipal Solid Waste (MSW) Landfill.

The disposal of municipal solid waste (MSW) directly at landfills or open dump areas, without segregation and treatment, is a significant concern due to its hazardous contents of antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARGs), and metal resistance genes (MGEs). The released leachate from landfills greatly effects the soil physicochemical, biological, and groundwater properties associated with agricultural activity and human health. The abundance of ARB, ARGs, and MGEs have been reported worldwide, including MSW landfill sites, animal husbandry, wastewater, groundwater, soil, and aerosol. This review elucidates the occurrence and abundance of ARB, ARGs, and MRGs, which are regarded as emerging contaminants (ECs). Recently, ECs have received global attention because of their prevalence in leachate as a substantial threat to environmental and public health, including an economic burden for developing nations. The present review exclusively discusses the demands to develop a novel eco-friendly management strategy to combat these global issues. This review also gives an intrinsic discussion about the insights of different aspects of environmental and public health concerns caused due to massive leachate generation, the abundance of antibiotics resistance (AR), and the effects of released leachate on the various environmental reservoirs and human health. Furthermore, the current review throws light on the source and fate of different ECs of landfill leachate and their possible impact on the nearby environments (groundwater, surface water, and soil) affecting human health. The present review strongly suggests the demand for future research focuses on the advancement of the removal efficiency of contaminants with the improvement of relevant landfill management to reduce the potential effects of disposable waste. We propose the necessity of the identification and monitoring of potential environmental and human health risks associated with landfill leachate contaminants.

A systematic approach for prioritizing landfill pollutants based on toxicity: Applications and opportunities

Landfills in the United States are a significant source of pollution to ground and surface water. Current environmental regulations require detection and/or monitoring assessments of landfill leachate for contaminants that have been deemed particularly harmful. However, the lists of contaminants to be monitored are not comprehensive. Further, landfill leachate composition varies over space and time, and thus the contaminants, and their corresponding toxicity, are not consistent across or within landfills. One of the main objectives of this study was to prioritize contaminants found in landfill leachate using a systematic, toxicity-based prioritization scheme. A literature review was conducted, and from it, 484 landfill leachate contaminants with available CAS numbers were identified. In vitro, in vivo, and predicted human toxicity data were collected from ToxCast, ECOTOX, and CTV Predictor, respectively. These data were integrated using the Toxicological Priority Index (ToxPi) for the 322 contaminants which had available toxicity data from at least two of the databases. Four modifications to this general prioritization scheme were developed to demonstrate the flexibility of this scheme for addressing varied research and applied objectives. The general scheme served as a basis for comparison of the results from the modified schemes, and allowed for identification of contaminants uniquely prioritized in each of the schemes. The schemes outlined here can be used to identify the most harmful contaminants in environmental media in order to design the most relevant mitigation strategies and monitoring plans. Finally, future research directions involving the combination of these prioritization schemes and non-target global metabolomic profiling are discussed.

Long-term redox conditions in a landfill-leachate-contaminated groundwater

Indicators of redox conditions; oxygen, sulphate, nitrate, ammonium, iron and manganese, and in addition, bicarbonate and total organic carbon were studied in groundwater samples contaminated by leachate emanating from Revdalen Landfill (Norway). Based on these variables, the study aimed to deduce the redox conditions in the aquifer. Literature on landfill leachate contamination of confined aquifers is scarce and to the best of our knowledge, this study, which describes long-term analysis of redox chemistry, is the first of its kind in such an environment. Groundwater samples were monitored for a period of 24 years, enabling us to describe redox conditions on both short-term and long-term bases. Levels of measured parameters in the contaminated aquifer varied spatially and with time, but were generally elevated except oxygen; pH (4.9–8.8), oxygen (0–11.3 mg/L), sulphate (0–28 mg/L), nitrate (0–16 mg N/L), ammonium (0.02–40 mg/L), iron (0–99 mg/L), manganese (0.06–16 mg/L), bicarbonate (22–616 mg/L) and total organic carbon (1.3–47 mg/L). From the result, levels of iron, manganese, nitrate and ammonium violated the Norwegian drinking water norms. However, iron, ammonium, total organic carbon and bicarbonate showed strong attenuation along the groundwater flow path. By contrast, oxygen, nitrate and sulphate increased farther out in the plume. The redox conditions that developed in the aquifer were similar to those previously reported for phreatic aquifers, structuring by proximity to the landfill as sulphate-reducing, iron-reducing, manganese-reducing, nitrate-reducing, and finally aerobic condition. Eventually, there was an apparent breakdown of this system due to ecosystem shift in the landfill when leachable reduced ions were depleted and the landfill became aerobic. Overall, the redox framework provided remarkable attenuation to contaminants, and thus prevented potential degradation of ecological health due to the landfill leachate.

Heavy metals in leachate, impacted soils and natural soils of different landfills in Malaysia: An alarming threat

Landfills are a potential threat to human health and the environment, especially from the detrimental and toxic heavy metals. This study focuses on the assessment of heavy metals contamination in leachate and surface soils from different landfills in Malaysia. Maximum quality rating scale (QRS) values of As (787) and Cr (552) denotes progressive deterioration of leachate contamination in landfill. The impacted soils showed high heavy metal concentrations especially at non-sanitary unlined landfills, as compared to background values, and natural soil nearby the landfills. In addition, to examine the environmental impacts of the landfill area (soil) in more detail, specific indexes; geo-accumulation index (Igeo), pollution index (PI) and integrated pollution index (IPI) were determined. Maximum As (3.122) and Cd (2.633) for Igeo and As (34.037) and Cd (20.881) for PI revealed that the soil samples in non-sanitary landfills were moderate to strongly polluted. The difference in range of IPI values for sanitary (0.294–0.322) and non-sanitary landfill soils (1.263–1.956) confirmed advanced decline of the soil quality in non-sanitary landfills. Arsenic concentrations were found to be statistically significant (ANOVA) for leachate and impacted soil in landfills investigated. It is also important to realize that rise in metal contents in landfill environments were not only caused by anthropogenic sources such as from the waste disposed, but also some other factors such as redox conditions, anoxic environments, pH, oxidation state of metals and microbial activities. Those conditions will actively promotes leaching of metals from waste and also natural soils in the landfill.

Simultaneous adsorption and biodegradation of trichloroethylene occurs in a biochar packed column treating contaminated landfill leachate

Trichloroethylene (TCE) is a human carcinogen that is commonly found in landfill leachate. Contaminated leachate plumes may be intercepted prior to reaching groundwater and treated in situ using permeable reactive barriers (PRB). This study used a packed column system containing herbal pomace and spruce biochar, previously shown to have TCE adsorptive capabilities. Influent containing raw or autoclaved landfill leachate was used to investigate the potential for environmental micro-organisms to establish a TCE-dechlorinating biofilm on the biochar, in order to prolong the operational life span of the system. TCE removal ≥ 99.7 % was observed by both biochars. No dichloroethylene (DCE) isomers were present in the column effluents, but cis-1,2 DCE was adsorbed to the biochar treating raw landfill leachate, indicating that dechlorination was occurring biologically in these columns. Known microbial species that are individually capable of complete dechlorination of TCE to ethene were not detected by 16S rRNA gene sequencing, but several species capable of partial TCE dechlorination (Desulfitobacterium spp., Sulfurospirillium spp. and Desulfuromonas spp) were present in the biofilms of the columns treating raw landfill leachate. These data demonstrate that biochar from waste material may be capable of supporting a dechlorinating biofilm to promote bioremediation of TCE.