Landfill Age Research Articles

Redox properties and dechlorination capacities of landfill-derived humic-like acids

Electron transfer capacities (ETC) of humic-like acids (HLA) and their effects on dechlorination are dependent on their redox-active properties. Aging and minerals can affect the chemical compositions and structures of HLA. However, the underlying mechanism and the impacts on the dechlorination capacities of HLA are poorly understood. We investigated how redox properties change in association with the intrinsic chemical natures and exterior minerals of the HLA extracted from landfilled solid wastes. Furthermore, the ETC of the landfill-derived HLA could be strengthened by increasing landfill age and demineralization, thereby facilitating the dechlorination of pentachlorophenol (PCP). The HLA molecules started to polymerize aromatic macromolecules during landfilling, leading to an increase in ETC and dechlorination capacities. Macromolecular HLA were dissociated to smaller molecules and exposed more aromatic and carboxyl groups when separated from minerals, which enhanced the ETC and the dechlorination abilities of the HLA. Microbial-mediated dechlorination was an effective way to degrade PCP, and almost 80% of the PCP was transformed after 40 days of demineralized HLA and Shewanella oneidensis MR-1 incubation. The demineralization and aging further facilitated the microbial-mediated PCP dechlorination. The findings provide a scientific base for improving in-situ bioremediation of chlorinated compound-contaminated soils using freshly synthesized HLA.

Risk for increased metal leakage due to ageing of landfills?

As landfill ages, oxygen will start to penetrate, We investigated whether aeration of a landfillaffected metal leaching, We found that aeration increased cation exchange capacity, butdecreased the buffering capacity and the metal-binding capacity. Leachates from an aeratedlandfill contained less than half the amount of aluminium and iron and more than double theamount of calcium, sulphur and zinc than leachates derived from an identical, but anaerobic,landfill. The leachate from the aerated landfill was capable of extracting metals from theoriginal landfill when recirculated. Leachate from the original landfill treated with leachatefrom the aerated landfill contained more than twice as much cadmium, copper, iron, sulphurand zinc than leachate from the identical anerobic landfill. We conclude that precautionsshould be taken considering the fate of deposited metals when extrapolating results derivedfrom studies on landfills at earlier degradation stages to landfills in more progressed phases.

Geotextile clogging at different stages of municipal solid waste landfills co-disposed with bottom ash

Co-disposal of bottom ash (BA) with municipal solid waste (MSW) in landfills is a common way for BA management. However, BA co-disposal in MSW landfills may accelerate geotextile clogging and reduce the performance of leachate collection system. This study compared geotextile clogging in a simulated MSW landfill leachate (MSWL) and a BA co-disposed landfill leachate (BAL) at different landfill stages. Geotextile clogging test was conducted using the MSWL and BAL taken from the simulated landfills on the 10th, 80th, 140th and 200th day, respectively. The results demonstrated that geotextile clogging varied with landfill age, due to the change of leachate characteristics. The mass of clogging material in geotextiles with BAL increased from 0.45 g to 2.74 g, which was 43.87%–63.73% greater than those with MSWL. The formation of biofilm was the main contributor for the geotextile clogging. At the same stage, the amount of biofilm formed on geotextile in different leachate was comparable. However, the amounts of CaCO3 precipitation on geotextile in BAL were 3.85–10.44 times of those in MSW leachate. The pH of leachate played a critical role in CaCO3 precipitation. The microbial analysis revealed that the co-disposal of the BA greatly influenced the microbial community diversity and structure.

Ex situ simultaneous nitrification-denitrification and in situ denitrification process for the treatment of landfill leachates

The objective of this research was to investigate the ex situ simultaneous nitrification–denitrification (SND) and in situ denitrification process and to evaluate its application for treating landfill leachates at long-term operations. Based on the predicted contaminant concentrations, two sets of laboratory-scale bioreactor landfill systems (an ex situ nitrification and in situ denitrification bioreactor as well as an ex situ SND and in situ denitrification bioreactor) were operated continuously for about 48 weeks. The recirculated leachate quantity and effluent characteristics of leachates were regularly monitored and analyzed by using the standard method. The ex situ SND and in situ denitrification process obtained a better leachate removal performance compared with the ex situ nitrification and in situ denitrification process, while the ex situ SND process can reduce the energy costs. However, the leachate treatment performance of this process was generally unsatisfactory as the contaminant concentrations do not meet the discharge standard within the forecasted time. These results further proved that the effectiveness of the treatment decreases along with an increasing landfill age. Therefore, further research must be performed to optimize the treatment efficiency of the bioreactor.

A review on the advanced leachate treatment technologies and their performance comparison: an opportunity to keep the environment safe.

Landfill application is the most common approach for biowaste treatment via leachate treatment system. When municipal solid waste deposited in the landfills, microbial decomposition breaks down the wastes generating the end products, such as carbon dioxide, methane, volatile organic compounds, and liquid leachate. However, due to the landfill age, the fluctuation in the characteristics of landfill leachate is foreseen in the leachate treatment plant. The focuses of the researchers are keeping leachate from contaminating groundwater besides keeping potent methane emissions from reaching the atmosphere. To address the above issues, scientists are required to adopt green biological methods to keep the environment safe. This review focuses on the assorting of research papers on organic content and nitrogen removal from the leachate via recent effective biological technologies instead of conventional nitrification and denitrification process. The published researches on the characteristics of various Malaysian landfill sites were also discussed. The understanding of the mechanism behind the nitrification and denitrification process will help to select an optimized and effective biological treatment option in treating the leachate waste. Recently, widely studied technologies for the biological treatment process are aerobic methane oxidation coupled to denitrification (AME-D) and partial nitritation-anammox (PN/A) process, and both were discussed in this review article. This paper gives the idea of the modification of the conventional treatment technologies, such as combining the present processes to make the treatment process more effective. With the integration of biological process in the leachate treatment, the effluent discharge could be treated in shortcut and novel pathways, and it can lead to achieving "3Rs" of reduce, reuse, and recycle approach.

The analysis of the possibility of using biological tests for assessment of toxicity of leachate from an active municipal landfill

One of the consequence of municipal waste deposition is the production of landfill leachate. Its volume and composition is determined by numerous factors, including waste composition, landfill age and the volume of precipitation. Leachate may contain a number of mineral and organic compounds, the volume of which must be controlled regularly. One of the methods of determining the toxicity of substances contained in landfill leachate is the use of biological tests, based − among others − on aquatic organisms sensitive to environmental contamination. The purpose of this study was to analyse the possibility of using ecotoxicological tests (supplementing the physical and chemical tests) for the purpose of assessment of landfill leachate toxicity. The tests were conducted at an operating municipal landfill in Stary Sącz (southern Małopolska Region, Poland N: 49°55’33”76, E: 20°65’68’70) from December 2015 to October 2016. The scope of the tests included the analysis of physical and chemical indicators as part of the landfill monitoring process, and also the analysis of additional selected indicators: namely the boron, barium and vanadium content. The selected ecotoxicological tests included tests using Daphnia magna Straus (Cladocera, Crustacea).Leachate tests conducted with the use of physical and chemical indicators have, for nearly twenty years, mainly demonstrated changes related to the age of the used landfill; besides increased boron and barium values, no evident contamination has been found, excluding the case of boron. However, a statistically significant correlation between the B and Ba contents and the amount of precipitation was determined. In two cases, the used biological tests have confirmed the toxicity of the leachate: in January and June 2016. In the same months, the highest and abnormal boron contents were measured, which could cause a toxic effect of leachates.

Characterization of wastewater from landfills - amount and type of humic substances extracted from leachate

This study aimed to characterize the humic substances (HS) extracted from landfills wastewater – leachates, with different ages of exploration. To reach the objective it was applied spectroscopy techniques, UV-Vis and FTIR spectra, as well as the ratio between the absorbance analysed. First, the HS were extracted, then fractionated in fulvic acids (FA) and humic acids (HA) and it was evaluated the phytotoxicity. HS content in the leachates were higher than the typical values found in the natural aquatic humic sources. It has been identified that the leachate HS, HA and FA aromatic fractions increased with the increase of the landfilling age, suggesting that the degree of humification increased with the landfilling age. All the HS showed a high aromaticity and humification degree. The HS extracts irrespective of their source presents similar structural composition. The functional groups found are in agreement with the literature: phenols, alcohols, carboxylic groups, aliphatic structures, among others. It was found that HA are mainly organic matter with a higher aromatic degree than FA. The HS and HA showed absence of phytotoxicity, testing by germination index, suggesting that may be used to produce liquid organic fertilizers.

A study on municipal leachate treatment through a combination of biological processes and ozonation

Landfill is the most commonly method of municipal solid waste disposal in many countries. This practice has great potential to produce highly polluted leachate in massive quantities, which can cause environmental contamination. Biological processes are known as a common method to treat municipal leachate however this process alone in is less effective, especially in reducing the concentration of organic pollutants (BOD5/COD ratio). Leachate properties are site-specific and greatly influenced by landfill age. This study focuses on the investigation of treatment methods that can increase the extent of leachate biodegradability by applying an ozone concentration of 2.5 mg/L with up to 360 minutes of contact time. In this study, batch reactors were used and operated in anaerobic and aerobic conditions. The leachate used here represents both young and old leachate. Several treatment combinations were compared: Variation I (a combination of biologically aerobic and anaerobic process), Variation II (ozonation included as a pre-treatment process), and Variation III (ozonation was included as a post-treatment process). The results suggest that the BOD5/COD ratios of young and old leachates were 0.58 and 0.21, respectively. The COD removal for a young and old leachate treatment by biological process alone was 96.8% and 50.8%, respectively. Meanwhile, a combination of anaerobic-ozonation-aerobic processes gave better COD removal. Ozonation had a significant effect on the old leachate treatment, where the COD removal rose from 50.8% to 75%. Ozonation is a type of technology that can be applied to a subsequence treatment of biological processes in order to elevate the COD removal efficiency.

Variations in the properties of leachate according to landfill age

Variations in the properties of leachate according to landfill age

An overview of municipal solid waste management and landfill leachate treatment: Malaysia and Asian perspectives.

Currently, generation of solid waste per capita in Malaysia is about 1.1kg/day. Over 26,500t of solid waste is disposed almost solely through 166 operating landfills in the country every day. Despite the availability of other disposal methods, landfill is the most widely accepted and prevalent method for municipal solid waste (MSW) disposal in developing countries, including Malaysia. This is mainly ascribed to its inherent forte in terms cost saving and simpler operational mechanism. However, there is a downside. Environmental pollution caused by the landfill leachate has been one of the typical dilemmas of landfilling method. Leachate is the liquid produced when water percolates through solid waste and contains dissolved or suspended materials from various disposed materials and biodecomposition processes. It is often a high-strength wastewater with extreme pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD), inorganic salts and toxicity. Its composition differs over the time and space within a particular landfill, influenced by a broad spectrum of factors, namely waste composition, landfilling practice (solid waste contouring and compacting), local climatic conditions, landfill's physico-chemical conditions, biogeochemistry and landfill age. This paper summarises an overview of landfill operation and leachate treatment availability reported in literature: a broad spectrum of landfill management opportunity, leachate parameter discussions and the way forward of landfill leachate treatment applicability.

Antibiotic Resistance Genes and Associated Microbial Community Conditions in Aging Landfill Systems.

Landfills receive about 350 million tons of municipal solid wastes (MSWs) per year globally, including antibiotics and other coselecting agents that impact antimicrobial resistance (AMR). However, little is known about AMR in landfills, especially as a function of landfill ages. Here we quantified antibiotics, heavy metals, and AMR genes (ARGs) in refuse and leachates from landfills of different age (<3, 10, and >20 years). Antibiotics levels were consistently lower in refuse and leachates from older landfills, whereas ARG levels in leachates significantly increased with landfill age (One-way ANOVA, F = 10.8, P < 0.01). Heavy metals whose contents increased as landfills age (one-way ANOVA, F = 12.3, P < 0.01) were significantly correlated with elevated levels of ARGs (Mantel test, R = 0.66, P < 0.01) in leachates, which implies greater AMR exposure risks around older landfills. To further explain ARGs distributional mechanisms with age, microbial communities, mobile genetic elements (MGEs) and environmental factors were contrasted between refuse and leachate samples. Microbial communities in the refuse were closely correlated with ARG contents (Procrustes test; M2 = 0.37, R = 0.86, P < 0.001), whereas ARG in leachates were more associated with MGEs.

Evolution of nitrogen species in landfill leachates under various stabilization states

In this study, nitrogen species in landfill leachates under various stabilization states were investigated with emphasis on organic nitrogen. Ammonium nitrogen was found to be approximately 1300mg/L in leachates from younger landfill units (less than 10years old), and approximately 500mg/L in leachates from older landfill units (up to 30years old). The concentration and aerobic biodegradability of organic nitrogen decreased with landfill age. A size distribution study showed that most organic nitrogen in landfill leachates is <1kDa. The Lowry protein concentration (mg/L-N) was analyzed and showed a strong correlation with the total organic nitrogen (TON, mg/L-N, R2=0.88 and 0.98 for untreated and treated samples, respectively). The slopes of the regression curves of untreated (protein=0.45TON) and treated (protein=0.31TON) leachates indicated that the protein is more biodegradable than the other organic nitrogen species in landfill leachates. XAD-8 resin was employed to isolate the hydrophilic fraction of leachate samples, and it was found that the hydrophilic fraction proportion in terms of organic nitrogen decreased with landfill age. Solid-state 15N nuclear magnetic resonance (NMR) was utilized to identify the nitrogen species. Proteinaceous materials were found to be readily biodegradable, while heterocyclic nitrogen species were found to be resistant to biodegradation.

A comparison of CH4, N2O and CO2 emissions from three different cover types in a municipal solid waste landfill

ABSTRACTHigh-density polyethylene (HDPE) membranes are commonly used as a cover component in sanitary landfills, although only limited evaluations of its effect on greenhouse gas (GHG) emissions have been completed. In this study, field GHG emission were investigated at the Dongbu landfill, using three different cover systems: HDPE covering; no covering, on the working face; and a novel material-Oreezyme Waste Cover (OWC) material as a trial material. Results showed that the HDPE membrane achieved a high CH4 retention, 99.8% (CH4 mean flux of 12 mg C m-2 h-1) compared with the air-permeable OWC surface (CH4 mean flux of 5933 mg C m-2 h-1) of the same landfill age. Fresh waste at the working face emitted a large fraction of N2O, with average fluxes of 10 mg N m-2 h-2, while N2O emissions were small at both the HDPE and the OWC sections. At the OWC section, CH4 emissions were elevated under high air temperatures but decreased as landfill age increased. N2O emissions from the working face had a significant negative correlation with air temperature, with peak values in winter. A massive presence of CO2 was observed at both the working face and the OWC sections. Most importantly, the annual GHG emissions were 4.9 Gg yr-1 in CO2 equivalents for the landfill site, of which the OWC-covered section contributed the most CH4 (41.9%), while the working face contributed the most N2O (97.2%). HDPE membrane is therefore, a recommended cover material for GHG control.Implications: Monitoring of GHG emissions at three different cover types in a municipal solid waste landfill during a 1-year period showed that the working face was a hotspot of N2O, which should draw attention. High CH4 fluxes occurred on the permeable surface covering a 1- to 2-year-old landfill. In contrast, the high-density polyethylene (HDPE) membrane achieved high CH4 retention, and therefore is a recommended cover material for GHG control.

Investigation of landfill leachate treatability for reuse in agricultural purposes

Leachates from landfills are one of the environmental challenges in developing countries, such as Iran that also will face water scarcity in the near future. Landfill leachate management to decrease the negative impact on water resources is indispensable. On the one hand, depending on the age of landfill, high ammonia concentration leachates could be a resource for use in agricultural purposes and on the other, treated leachate can be used as a valuable resource for agronomic irrigation. In order to investigate this hypothesis, landfill leachate was provided from the Sari municipal landfill in the north of Iran (COD = 7,045 mg/l; BOD5/COD = 0.36) and the performance of different combinations of biological, chemical and membrane processes were evaluated according to Iran's Agricultural Water Standard (IAWS). The treatment processes consisted of sequencing batch reactor (SBR), Fenton's process/SBR, and membrane/SBR/Fenton. Results indicated in addition to access IAWS, the treated leachate through Membrane/SBR/Fenton's process could be used as a nitrogen source for agricultural purposes. The removal efficiency of primary parameters, including COD, BOD5, turbidity, and color were 89%, 96%, 99% and 98%, respectively.

Australia-wide assessment of perfluoroalkyl substances (PFASs) in landfill leachates

Leachate from 27 landfills was analysed for nine perfluoroalkyl substances (PFASs). Five PFASs were detected ubiquitously, with perfluorohexanoate (PFHxA) the predominant PFAS (mean 1700ng/L; range 73–25,000ng/L). Despite the complexity of landfill-specific factors, some general trends in PFAS concentrations were observed. Mean concentrations of eight PFASs were higher in operating landfills (or landfill cells) accepting primarily municipal waste, compared to closed municipal landfills. Landfills accepting primarily construction and demolition wastes produced leachate that had higher mean PFAS concentrations than municipal landfills. Younger landfills appeared to have a higher burden of waste containing PFASs (or their precursors), as significant relationships (p<0.05) were observed between selected PFAS concentrations and landfill age. Increasing pH and total organic carbon (TOC) in leachate were associated with increased concentrations of several PFASs. Eight landfills discharged leachate to wastewater treatment plants (WWTPs). Estimated masses of PFASs discharged reached a maximum of 62g annually (PFHxA), with a national estimate reaching 31kg (PFHxA) annually. The practise of treating leachate at WWTPs allows redistribution of PFASs between the solid and liquid waste streams, although the contribution of leachate to the total load of PFASs entering WWTPs is minor compared to domestic waste water sources.

Leachate Treatment by Heterogeneous Fenton on an Activated Carbon Substrate with Fe(II) Impregnated

Organic components contained in leachates resulting from decomposition of waste are difficult to degrade. They also contain inorganic components, as nitrogen compounds, phosphates, and chlorides, also Ca, Mg, K, and heavy metals. Leachate volume and its composition vary depending on biogeochemistry of type site of deposited residues, and age of sanitary landfill. In this study, it conducted a Heterogeneous Fenton, advanced oxidation process using lignitic activated carbon as solid matrix, with and without Fe2+ impregnation, for the treatment of leachate (Le) obtained from a sanitary landfill located in the city of Mérida, Yucatan, Mexico. In this study was determined the efficiency of Heterogeneous Fenton process for to remove Chemical Oxygen Demand (COD) and Color from crude leachates using mesoporous activated carbon, previously treated with HCl, HNO3, and a mixture of both acids and impregnated with Fe2+ on actived carbon. It was studied of activated carbon behavior previously treated with each acid and the mixture, washed with hot water and impregnated with Fe2+ using FeCl2.4H2O and FeSO4·7H2O salts. For leachate treatment by Heterogeneous Fenton reaction, it was selected carbon pretreatment with HCl acid and impregnation with FeSO4·7H2O. Treatment with HCl presented the advantage of not prematurely oxidize to Fe2+. In order to select an optimal dose and achieve an adequate concentration of HO· radicals dosage tests was carried out H2O2. By selecting the indicated procedure, it was obtained more than 80% performance in removing COD and Color from crude leachate. The confidence level for the selected variables (acids and impregnation) was determined by a statistical analyzes using the Centurion XVII software. Finally, mesoporous lignitic carbon used in this study was found to be adequate for this oxidation process, and this method presented the advantage of not producing sludge as in traditional Fenton reaction.

Co-occurrence of mobile genetic elements and antibiotic resistance genes in municipal solid waste landfill leachates: A preliminary insight into the role of landfill age

Since municipal solid waste (MSW) landfill harbours miscellaneous wastes, pollutants and microorganisms, it gradually becomes a huge potential reservoir for breeding antibiotic resistance genes (ARGs). The objective of this study was to determine the prevalence and diversity of ARGs associated with various mobile genetic elements (MGEs) in MSW landfill leachates. The relationship of ARGs with leachate characteristics was also studied to explore the influence of landfill age. Seven sulfonamides (sulfapyridine, sulfadiazine, sulfathiazole, sulfamethoxazole, sulfamerazine, sulfamethazine and sulfaquinoxaline), three encoded ARGs (sul-I, sul-II and sul-III) and four types of MGEs (plasmids, transposons, integrons and insertion sequences) were quantified in leachates with landfill ages ranging from 3 months–6 years. ARGs increased to an absolute concentration of 106 copies/μL and were positively correlated (p < 0.05) to MGEs. Significant correlations (p < 0.05) were also discovered among ARGs and the increasing humic acids, heavy metals (Zn, Cu and Co) and antibiotics (except for sulfathiazole and sulfaquinoxaline), implying landfilling might contribute to the enrichment of ARGs in the long-term. Non-target full scans revealed the role of persistent unknown compounds in stimulating the ARGs dissemination. Overall, this study demonstrates the exacerbation of ARGs pollution in landfill environment and a detailed delineation of the complex inter-relationships between ARGs and the substances harbouring in landfills is badly required.

Compositional and physicochemical changes in waste materials and biogas production across 7 landfill sites in UK

The aim of this study was to evaluate the spatial distribution of the paper and fines across seven landfill sites (LFS) and assess the relationship between waste physicochemical properties and biogas production. Physicochemical analysis of the waste samples demonstrated that there were no clear trends in the spatial distribution of total solids (TS), moisture content (MC) and waste organic strength (VS) across all LFS. There was however noticeable difference between samples from the same landfill site. The effect of landfill age on waste physicochemical properties showed no clear relationship, thus, providing evidence that waste remains dormant and non-degraded for long periods of time. Landfill age was however directly correlated with the biochemical methane potential (BMP) of waste; with the highest BMP obtained from the most recent LFS. BMP was also correlated with depth as the average methane production decreased linearly with increasing depth. There was also a high degree of correlation between the Enzymatic Hydrolysis Test (EHT) and BMP test results, which motivates its potential use as an alternative to the BMP test method. Further to this, there were also positive correlations between MC and VS, VS and biogas volume and biogas volume and CH4 content. Outcomes of this work can be used to inform waste degradation and methane enhancement strategies for improving recovery of methane from landfills.

Tracking changes in fluorescent organic composition in leachates using excitation emission matrix-parallel factor analysis

Abstract Landfill and composting are the most important treatment methods for municipal solid waste containing a significant proportion of organic matter. With time the landfill leachate undergoes changes through humification and mineralisation. The influence of landfill age on temporal changes in leachate composition when exposed to different environmental conditions is discussed. The study is based on 3 years monitoring of leachate from a landfill site in Adelaide, Australia and the investigation uses size exclusion chromatography and an excitation emission matrix approach combined with parallel factor analysis. This study showed that the matured leachate contained a broad range of low molecular weight organics with less aromaticity. Fluorescent analysis showed less-matured leachate contained more bio-polymer components. Leachate exposed to ponds showed microbial activity but the biopolymer percentage decreased with increased duration of exposure. The parallel factor analysis revealed four major components (C1–C4) at excitation/emissions of C1: 240/440 nm and 205/440 nm, C2: 225/490 nm and 225/420 nm, C3: 215/390 nm and 215/445 nm, and C4: 250/465 nm. These four components represented humic and fulvic acid-like organics of different molecular compositions. The results demonstrated that environmental variation had a direct effect on the mineralisation and humification of organic matter.

Characterizing the compositional variation of dissolved organic matter over hydrophobicity and polarity using fluorescence spectra combined with principal component analysis and two-dimensional correlation technique.

Dissolved organic matter (DOM) obtained from three leachates with different landfill ages was fractionated, and its compositional variation based on hydrophobicity and polarity was characterized by synchronous fluorescence spectra combined with principal component analysis (PCA) and two-dimensional correlation technique. The results showed that the bulk DOM and its fractions were comprised of tryosine-, tryptophan-, fulvic-, and humic-like substances. Tyrosine-like matter was dominant in the young leachate DOM and its fractions, while tryptophan-, fulvic-, and humic-like substances were the main components in the intermediate and old leachate DOMs and their fractions. Tryosine-, tryptophan-, fulvic-, and humic-like substances varied concurrently with the hydrophobicity and polarity. However, the change ratio of these substances was different for the three leachates. Tyrosine-like matter, humic-like materials, and fulvic-like substances were the most sensitive to the hydrophobicity and polarity in the young, intermediate, and old leachates, respectively. Such an integrated approach jointly enhances the characterization of the hydrophobicity- and polarity-dependent DOM fractions and provides a promising way to elucidate the environmental behaviors of different DOM species.