Compounds In Landfill Leachate Research Articles

Removal performance of leonardite toward volatile organic compounds and toxic metals from landfill leachates

AbstractLeachate from municipal waste contains volatile organic compounds and potentially toxic metals. The leaching of which into water sources also jeopardizes access to clean water. Therefore, reducing the concentration of pollutants in leachate is important to reduce health risks and environmental pollution. In this study, the efficacy of granulated organic leonardite added to leachate from municipal waste in reducing the toxic concentrations of the leachate for different time points (30, 60, 90, and 120 min) at a shaking speed of 200 rpm was investigated. Results demonstrated that leonardite significantly removed various contaminants, including organic acids (71.16%), alcohols (74.31%), aldehydes (68.01%), esters (78.28%), ethers (81.03%), ketones (68.52%), hydrocarbons (84.25%), N compounds (78.56%), S compounds (80.67%), organic N (86.01%), total Kjeldahl nitrogen (93.26%), NH4‐N (84.83%), NO3‐N (89.30%), SO4 (76.62%), PO4 (73.85%), organic C (50.07%), Hg (96.80%), Pb (95.99%), Cu (82.68%), Al (65.56%), total Cr (98.11%), Cd (99.28%), Li (96.31%), Ni (97.27%), and As (67.79%). The leonardite granules used in this study showed high adsorption and removal performance for organic/inorganic and volatile compounds in landfill leachate. These results indicate that leonardite can be a suitable adsorption material for leachate pretreatment. However, it is necessary to perform a durability test to use the material in the long term as a covering on landfills.

Validation of UV/persulfate as a PFAS treatment of industrial wastewater and environmental samples

The contamination of natural water and industrial wastewater with per- and polyfluoroalkyl substances (PFAS) occurs globally. Thus, proper technologies are required to reduce PFAS in the environment and mitigate the adverse effects of these pollutants on human health and the environment. This study used a 23 full factorial design to evaluate the importance of operating factors including the level of persulfate (PS), the initial concentration of PFAS, and the time to the photochemical degradation of PFAS via ultraviolet irradiation at 185/254 nm assisted with persulfate (PS/UV method) in spiked solution. The method was then applied to break down PFAS in industrial wastewater, landfill leachate and groundwater samples using the highest factor levels applied in the 23 full factorial design. The results showed that the three investigated factors played an important role in the degradation of PFAS. The highest PFAS degradation was 57 % perfluorobutanoic acid (PFBA), 80 % perfluorooctanoic acid (PFOA) and 60 % perfluorooctane sulfonate (PFOS) using 10 mg L−1 PFAS, 5 g L−1 PS for 4 h. The defluorination also increased in the presence of PS but decreased in the presence of potassium hydrogen phthalate, nitrates, and chlorides. The PS/UV method decreased the concentration of PFAS in wastewater samples by 20–25 % PFOS and 13–15 % perfluorohexane sulfonate (PFHxS). PFAS degradation in wastewater improved with increasing treatment time. Under the PS/UV treatment, the degradation of major PFAS in groundwater was 94 % 6–2 FTS, 75 % PFOA, 62 % PFOS and 61 % PFHxS. The removal of major compounds in landfill leachate reached up to 12 % PFHxA, 32 % PFPeA, 56 % PFOA and 43 % PFOS. Our study indicated matrix effects leading to decreased PFAS degradation in different contaminated waters. The level of PS should also be controlled to an optimal value because higher levels led to a decrease in treatment efficiency.

Assessing the Fate of Dissolved Organic Compounds in Landfill Leachate and Wastewater Treatment Systems.

Landfill leachate and municipal wastewater are major sources of chemical pollutants that contaminate our drinking water sources. Evaluating the dissolved organic chemical composition in wastewater treatment plants is therefore essential to understand how the discharge impacts the environment, wildlife, and human health. In this study, we utilized a nontargeted analysis method coupling liquid chromatography and tandem mass spectrometry (LC-MS/MS) to analyze chemical features at different points along two landfill leachate treatment plants (LLTPs) and two municipal wastewater treatment plants (WWTPs) in the Southeastern United States. Significant feature differences were observed for the WWTPs where activated sludge clarification was employed versus the LLTPs utilizing reverse osmosis. Specifically, even though both LLTPs had the largest number of features in their influent water, their effluent following reverse osmosis yielded a lower number of features than the WWTPs. Additionally, the clarification processes of each WWTP exhibited different efficiencies as chemical disinfection removed more features than UV disinfection. Feature identification was then made using the LC, MS, and MS/MS information. Analysis of the identified molecules showed that lipids were the most effectively removed from all plants, while alkaloid and organic nitrogen compounds were the most recalcitrant.

Efficient degradation of organic compounds in landfill leachate via developing bio-electro-Fenton process

Efficient and harmless disposal of landfill leachate has attracted increasing attention. In this study, the bio-electro-Fenton method was investigated and developed to degrade the organic compounds in landfill leachate by hydroxyl radical oxidation. The optimal operational parameters (i.e., pH and external voltage) of the bio-electro-Fenton system were detected. Under the conditions of pH 2, 0.6 V, the highest total chemical oxygen demand (COD) decrement efficiency was obtained (about 70%), with apparent removal constant at 6 h (kapp-6h) of about 0.12 h−1. Subsequently, to further increase the degradation efficiency, functionalized carbon black and functionalized carbon nanotube (FCNT) were prepared as catalysts for the cathode electrode modification. With 0.4 mg/cm2 FCNT coated on the cathode electrode, 91.3% of the organic compounds were degraded, remaining only 84 mg/L COD (kapp-6h = 0.24 h−1). In all the reactors, the COD was mainly decreased in 0–6 h, contributing to over 68% of the total degradation efficiency. In the bio-electro-Fenton system, the bio-anode electrode could enhance H2O2 production and the conversion between Fe2+ and Fe3+ by strengthening electrons generation and transportation via the oxidation of organics by biofilms (dominant with Geobacter) covered on the carbon brush.

Adsorption behavior of bisphenol A on bentonite-loess mixtures.

The leakage of chemical compounds in landfill leachate led to serious environment pollution, especially, the compounds termed endocrine disruptors such as bisphenol A (BPA). It is very important to study the adsorption behavior of endocrine disruptors in modified soil for predicting and evaluating the potential harm of endocrine disruptors to the soil. Bentonite-amended Chinese loess mixtures, with various proportions of bentonite, were used for the removal of BPA from an aqueous solution. A batch test was used to investigate the adsorption properties of bisphenol A on bentonite and Chinese loess mixtures. The influences of bentonite proportion, temperature, reaction time, pH, and soil-water ratios on the adsorption process were considered. The Fourier transform infrared spectra (FTIR) was used to clarify the change of functional groups before and after the adsorption of BPA on soil. The adsorption mechanism of BPA on soil was discussed preliminary. The results show that the addition of bentonite to the loess can improve the adsorption rate of BPA. The adsorption of BPA was mainly a spontaneous, exothermic, entropy decreasing physical adsorption process. The interaction between bentonite content and reaction concentration had a beneficial effect on BPA adsorption. The linear relationship between bentonite content and adsorption capacity was obtained. The results indicate that bentonite amended loess can provide a good liner for BPA.

Exploring indirect photolysis of 6:2 fluorotelomer sulfonate in landfill leachate under simulated sunlight: effect of humic acid and nitrate.

Landfill leachate is exposed to sunlight through on- and off-site leachate treatment and disposal to surface water bodies. Very little is known about the potential phototransformation of fluorotelomer compounds in landfill leachates, which can undergo environmental oxidation and produce perfluorocarboxylic acids (PFCAs). This study investigated phototransformation of spiked 6:2 fluorotelomer sulfonate (FTS) (∼ 100 μg/L) in leachate under simulated sunlight, using a metal halide lamp (wavelength, 390 to 750 nm). To understand the effects of nitrate and humic acid (HA), phosphate buffer (pH 7.1) containing nitrate and HA were spiked with 6:2 FTS and irradiated under simulated sunlight for 72 h. Following irradiation, 6:2 FTS and known transformation products (i.e., PFCAs) were quantified in the samples using LC-MS/MS. The results showed that 6:2 FTS was undergoing indirect photolysis in leachate (half-life of ∼ 15 days), suggesting that indirect photolysis of 6:2 FTS is likely a relevant transformation pathway in sunlit aquatic environments. However, the spiked 6:2 FTS did not show any observable decrease in the presence of nitrate and HA over 72 h. Perfluorohexanoic acid (PFHxA) increased in irradiated leachate background samples (without 6:2 FTS spike) suggesting that phototransformation in sunlit leachate could lead to the formation of persistent PFCAs at environmental concentrations of the precursors. Future studies using probe compounds are recommended to better understand the roles of reactive species in phototransformation of 6:2 FTS.

Decreased formation of disinfection by-products during electrochemical leachate oxidation and their post-removal by electro-adsorption

Membrane electrochemical reactor (MER) is an effective treatment system to remove recalcitrant compounds in landfill leachate but harmful byproducts can be formed during the treatment. Herein, we have investigated the formation of total halogenated organics and the associated toxicity as a side effect of leachate treatment by the MER. Those byproducts are represented by the term “disinfection byproducts, or DBPs”, because of the similar formation mechanisms. Several DBP groups were detected during the leachate treatment; however, the amount of DBP generated in the MER only accounted for 19.1 ± 4.5% of that in a membrane-less electrooxidation system (control). Likewise, the total toxicity value in the MER effluent was 26.6 × 10−3, only 15.1% of that in the control system. While trihalomethanes dominated mass concentration by 84.1% in the MER, haloacetonitriles contributed to majority of the additive toxicity due to their higher toxicity index. Increasing the initial leachate pH from 9.5 to 13 could increase the DBP concentration by 2.18 times because of less removal of humic acids. A high initial ammonia concentration of 6000 mg L−1 resulted in the increased DBP formation by 146.8%, compared to that with 2500 mg L−1, due to the increased formation of nitrogenous DBPs. A higher current density of 30 mA cm−2 doubled the DBP formation because of a faster reaction rate and a higher solution temperature. The extended treatment time caused trihalomethanes to continue forming DBP and degradation of most DBPs to some extent. With removing 67.5% of DBP mass concentration and 74.4% of the additive toxicity, the GAC-electrode system was shown more effective than GAC adsorption alone in remediating DBP from the MER effluent.

Formation of perfluorocarboxylic acids from 6:2 fluorotelomer sulfonate (6:2 FTS) in landfill leachate: Role of microbial communities

Fluorotelomer compounds in landfill leachate can undergo biotransformation under aerobic conditions and act as a secondary source of perfluorocarboxylic acids (PFCAs) to the environment. Very little is known about the role of various microbial communities towards fluorotelomer compounds biotransformation. Using an inoculum prepared from the sediment of a leachate collection ditch, 6:2 fluorotelomer sulfonate (6:2 FTS) biotransformation experiments were carried out. Specific substrates (i.e., glucose, ammonia) and ammonia-oxidizing inhibitor (allylthiourea) were used to produce two experimental runs with heterotrophic (HET) growth only and heterotrophic with ammonia-oxidizing and nitrite- oxidizing bacteria (HET + AOB + NOB). After 10 days, ∼20% of the spiked 6:2 FTS removal was observed in HET + AOB + NOB, compared to ∼7% under HET condition. Higher 6:2 FTS removal in HET + AOB + NOB likely resulted from ammonia monooxygenase enzyme that catalyzes the first step of ammonia oxidation. The HET + AOB + NOB condition also showed higher PFCA (C4–C6) formation (∼2% of initially spiked 6:2 FTS), possibly due to higher overall bioactivity. Microbial community analysis through 16s rRNA sequencing confirmed that Proteobacteria and Bacteroidetes were the most abundant phyla (>75% relative abundance) under all experimental conditions. High abundance of Actinobacteria (>17%) was observed under the HET + AOB + NOB condition on day 7. Since Actinobacteria can synthesize a wide range of enzymes including monooxygenases, they likely play an important role in 6:2 FTS biotransformation and PFCA production.

The effect of sodium percarbonate dose on the reduction of organic compounds in landfill leachate

The paper discusses the issue of using classic Fenton’s reagent modification for pre-treatment of leachate from a landfill in Janczyce (Świętokrzyskie Voivodeship, Poland) – sodium percarbonate (2Na2CO3·3H2O2) was used as an alternative source of hydrogen peroxide, and hydrated iron sulphate ((II) FeSO4·7H2O) was the source of iron ions. The tests were carried out at initial process pH = 3, for different doses of the Fe2+ catalyst (ranging within 100÷5400 mgFe/L), and for mass ratio iron (II) to sodium percarbonate – 1:3. Three doses were selected after this stage, for which the following parameters were examined: the effect of initial process pH ranging between 2 and 4, the effect of oxidation process duration (30÷150 min.), and the effect of the ratio Fe2+ to sodium percarbonate (1:3, 1:5 and 1:7). The values of selected parameters (pH, COD, TOC) in leachates, both before and after the treatment process have been determined according to applicable standards. Completed tests have proven, inter alia, that the proposed implementation of the Fenton’s method with sodium percarbonate may be an effective alternative for hydrogen peroxide as an oxidiser; with an increasing dose of the 2Na2CO3.3H2O2, the improvement in landfill leachate remediation efficiency measured by decreasing TOC and COD values reaches certain extent only; the process modified with sodium percarbonate may be effective already at pH=4.

Microalgal bioremediation of nitrogenous compounds in landfill leachate – The importance of micronutrient balance in the treatment of leachates of variable composition

Landfill leachate is a type of wastewater which is challenging to treat. Phycoremediation has been proposed as an alternative biological treatment for removal of ammonia nitrogen. Several studies have shown microalgae based bioremediation to be possible with ammonia tolerant microalgal species, provided that an optimal dilution is used and the initial molecular N:P ratio is adjusted.The composition of landfill leachate varies between sites and throughout the year. The performance of selected microalgal strains and their susceptibility to variation in landfill leachate composition is poorly understood. This study compares the growth of Chlamydomonas sp. strain SW15aRL in a variety of leachate samples. The leachate samples are from different sites including leachate sampled on different occasions from the same site. These substrates were diluted to obtain ammonia nitrogen concentration within the range of 30 to 220 mg·l−1.Results showed that strain SW15aRL was capable of growth in a variety of leachates but was dependent on the overall composition profile of the landfill leachate rather than just its dilution. Growth was negatively affected in two of the leachates tested, due to metal toxicity and mineral bioavailability or deficiency. Phosphate addition was essential for growth in the landfill leachates even though precipitation occurred in some instances. Ammonia nitrogen decrease varied between 70% and 100% in the substrates where microalgae could successfully grow.This study indicates that due to their overall mineral profile some landfill leachates are more suited for microalgae based remediation than others. Furthermore, this study indicates that a better understanding of other physicochemical processes that take place concurrently during the growth of microalgae in landfill leachate and which contribute to overall nutrient reduction is required.

PHOTODEGRADATION OF NON-BIODEGRADABLE ORGANIC COMPOUNDS IN LANDFILL LEACHATE BY Mn-TiO2-BENTONITE

The photocatalytic process helps to enhance biodegradability of landfill leachate. TiO2-bentonite nanocrystalline powders with various Mn-doping levels were synthesized by the sol–gel process using TiCl4 and manganese nitrate as precursors. The synthesized nanomaterials were characterized by X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray analysis (EDX). The experimental results indicated that the removal of chemical oxygen demand (COD), biological oxygen demand (BOD5), total organic carbon (TOC) and color by 2%Mn-TiO2-bentonite photocatalyst could be reached more than 81%, 83%, 65% and 96%, respectively. Under optimal conditions, the BOD5/COD ratio was elevated from 0.08 to 0.40. The organic compounds in landfill leachate before and after treatment using Mn-TiO2-bentonite photocatalyst were analyzed by means of high performance liquid chromatography (HPLC). The analysis result of HPLC diagrams revealed phenol, p-nitrophenol, p-crezol and some kinds of organic pollutants in the landfill leachate were totally decomposed after 12 h of treatment. Moreover, the re-usability of Mn-TiO2-bentonite catalysts was also studied with good efficiency. It was concluded that the Mn-TiO2-bentonite photocatalyst could be a cost-effective method for the pre-treatment of non-biodegradable organic pollutants in the landfill leachate.

Two-stage Anaerobic Membrane Bioreactor (AnMBR) system to reduce UV absorbance in landfill leachates

Landfill leachate typically contains UV-quenching organics, which hinder disinfection at POTWs. This study tested a 2-stage submerged AnMBR for the degradation of UV-absorbing compounds in landfill leachate. Leachate was treated in a thermophilic reactor (55 ± 2 °C) followed by a mesophilic AnMBR (37 ± 1 °C), with HRTs of 25 ± 5 days and 40 ± 5 days respectively. Solids were not wasted, in order to promote biomass accumulation. COD, Organic carbon, and UV254 absorbance were monitored over 13 months of operation. Known UV-quenching compounds, including humic acids, fulvic acids and hydrophilic matter, were reduced by 55%. Molecular weight distribution analyses revealed that the thermophilic reactor hydrolyzed organic carbon >100 KDa into smaller fractions, which were removed in the AnMBR. The system consistently removed 50% of the total UV absorbance. This promising, new enhanced biological process may provide landfills with a feasible pretreatment alternative to expensive chemical oxidation or RO processes before discharging leachate into sewers.

Identification of organic compounds in landfill leachate treated by advanced oxidation processes

ABSTRACTLandfill leachates are considered to be complex effluents of a variable composition containing many biorecalcitrant and highly toxic compounds. Considering the shortage of studies concerning the treatment of landfill leachates using ozone, as well as its combination with catalysts, the aim of this paper was to identify the organic compounds in this effluent treated with advanced oxidation processes (AOPs) of ozonation (O3), and heterogeneous catalytic ozonation with TiO2 (O3/TiO2) and with ZnO (O3/ZnO). In addition, this study sought to assess the efficiency of the removal of the organic matter present in the leachate. For the pre- and post-AOPs, the leachate was characterized through physicochemical parameters and identification of organic compounds using gas chromatography coupled to the mass spectrometry (GC-MS). The three processes studied (O3, O3/TiO2, and O3/ZnO) presented color removal, turbidity, BOD above 95%, and lower COD removals (19%, 24%, and 33%, respectively). All AOPs studied promoted a similar reduction of organic compounds from leachate, some of which with toxic and carcinogenic potential, such as p-cresol, bisphenol A, atrazine, and hexazinone. In addition, upon the removal of organic matter and organic compounds, the heterogeneous catalytic ozonation processes proved more efficient than the process carried out only with ozone.

Simultaneous energy generation and UV quencher removal from landfill leachate using a microbial fuel cell.

The presence of UV quenching compounds in landfill leachate can negatively affect UV disinfection in a wastewater treatment plant when leachate is co-treated. Herein, a microbial fuel cell (MFC) was investigated to remove UV quenchers from a landfill leachate with simultaneous bioelectricity generation. The key operating parameters including hydraulic retention time (HRT), anolyte recirculation rate, and external resistance were systematically studied to maximize energy recovery and UV absorbance reduction. It was found that nearly 50% UV absorbance was reduced under a condition of HRT 40days, continuous anolyte recirculation, and 10Ω external resistance. Further analysis showed a total reduction of organics by 75.3%, including the reduction of humic acids, fulvic acids, and hydrophilic fraction concentration as TOC. The MFC consumed 0.056kWhm-3 by its pump system for recirculation and oxygen supply. A reduced HRT of 20days with periodical anode recirculation (1 hour in every 24 hours) and 39Ω external resistance (equal to the internal resistance of the MFC) resulted in the highest net energy of 0.123kWhm-3. Granular activated carbon (GAC) was used as an effective post-treatment step and could achieve 89.1% UV absorbance reduction with 40gL-1. The combined MFC and GAC treatment could reduce 92.9% of the UV absorbance and remove 89.7% of the UV quenchers. The results of this study would encourage further exploration of using MFCs as an energy-efficient method for removing UV quenchers from landfill leachate.

Organic matters removal from landfill leachate by immobilized Phanerochaete chrysosporium loaded with graphitic carbon nitride under visible light irradiation

This study investigated the technical applicability of a combination of Phanerochaete chrysosporium (P. chrysosporium) with photocatalyst graphitic carbon nitride (g-C3N4) for organic matters removal from landfill leachate under visible light irradiation. Photocatalyst g-C3N4 was well immobilized on the hyphae surface of P. chrysosporium by calcium alginate. The typical absorption edge in visible light region for g-C3N4 was at about 460 nm, and the optical absorption bandgap of g-C3N4 was estimated to be 2.70 eV, demonstrating the great photoresponsive ability of g-C3N4. An optimized g-C3N4 content of 0.10 g in immobilized P. chrysosporium and an optimized immobilized P. chrysosporium dosage of 1.0 g were suitable for organic matters removal. The removal efficiency of total organic carbon (TOC) reached 74.99% in 72 h with the initial TOC concentration of 100 mg L−1. In addition, the gas chromatography coupled with mass spectrometry (GC-MS) measurements showed that immobilized P. chrysosporium presented an outstanding removal performance for almost all organic compounds in landfill leachate, especially for the volatile fatty acids and long-chain hydrocarbons. The overall results indicate that the combination P. chrysosporium with photocatalyst g-C3N4 for organic matters removal from landfill leachate may provide a more comprehensive potential for the landfill leachate treatment.

Municipal solid waste-derived biochar for the removal of benzene from landfill leachate.

The potential of biochar, produced from fibrous organic fractions of municipal solid waste (MSW), for remediation of benzene, one of the frequently found toxic volatile organic compounds in landfill leachate, was investigated in this study based on various environmental conditions such as varying pH, benzene concentration, temperature and time. At the same time, landfill leachate quality parameters were assessed at two different dump sites in Sri Lanka: Gohagoda and Kurunegala. MSW biochar (MSW-BC) was produced by slow temperature pyrolysis at 450°C, and the physiochemical characteristics of the MSW-BC were characterized. All the leachate samples from the MSW dump sites exceeded the World Health Organization permissible level for benzene (5µg/L) in water. Removal of benzene was increased with increasing pH, with the highest removal observed at ~pH 9. The maximum adsorption capacity of 576µg/g was reported at room temperature (~25°C). Both Freundlich and Langmuir models fitted best with the equilibrium isotherm data, suggesting the involvement of both physisorption and chemisorption mechanisms. Thermodynamic data indicated the feasibility of benzene adsorption and its high favorability at higher temperatures. The values of [Formula: see text] suggested physical interactions between sorbate and sorbent, whereas kinetic data implied a significant contribution of chemisorption. Results obtained from FTIR provided clear evidence of the involvement of functional groups in biochar for benzene adsorption. This study suggests that MSW biochar could be a possible remedy for benzene removal from landfill leachate and at the same time MSW can be a potential source to produce biochar which acts as a prospective material to remediate its pollutants while reducing the volume of waste.

Enhanced biodegradation of phenolic compounds in landfill leachate by enriched nitrifying membrane bioreactor sludge

The role of autotrophic nitrification on the biodegradation of toxic organic micro-pollutants presented in landfill leachate was assessed. A two-stage MBR system consisting of an inclined tube incorporated anoxic reactor followed by aerobic submerged membrane reactor was operated under long sludge age condition in which nitrifying bacteria could be enriched. During the reactor operation, organic removal efficiencies were more than 90% whereas phenolic compounds including bisphenol A (BPA) and 4-methyl-2,6-di-tert-butylphenol (BHT) were removed by 65 and 70% mainly through biodegradation in the aerobic reactor even at high feed concentrations of 1000μg/L for both compounds. Batch experiments revealed that enriched nitrifying sludge with nitrifying activities could biodegraded 88 and 75% of BPA and BHT, largely improved from non-nitrifying sludge and enriched nitrifying sludge with the presence of inhibitor. The first-order kinetic rates of BHT and BPA removal were 0.0108 and 0.096h−1, also enhanced by 44% from the non-nitrifying sludge.

Treatment of landfill leachate using immobilized Phanerochaete chrysosporium loaded with nitrogen-doped TiO2 nanoparticles

This study investigated the performance of immobilized Phanerochaete chrysosporium loaded with nitrogen-doped TiO2 nanoparticles in the treatment of raw landfill leachate with a very low biodegradability ratio (BOD5/COD) of 0.09. The effects of various operating parameters, such as initial chemical oxygen demand (COD) concentration, pH, temperature, and biosorbent dosage, were evaluated with respect to the removal efficiency of total organic carbon (TOC) and ammonia nitrogen (NH3–N). For the immobilized biosorbents, an optimum pH of 6.0 for TOC and 7.0 for NH3–N were found suitable for TOC and NH3–N removal at temperature of 37°C, respectively. The most superior removal efficiencies of TOC and NH3–N of landfill leachate were over 75% and 74% in 72h at an initial COD concentration of 200mgL−1, respectively. In addition, heavy metals were partly removed by the immobilized biosorbents during the process of landfill leachate treatment. The species and mass percentage of organic compounds in landfill leachate after the treatment were found to have considerably declined according to the gas chromatography coupled with mass spectrometry (GC–MS) system. These results indicate that the immobilized P. chrysosporium loaded with nitrogen-doped TiO2 nanoparticles could be a convenient and efficient method for the treatment of landfill leachate.

Landfill leachate treatment with Mn and Ce oxides impregnated GAC–ozone treatment process

Abstract Mn and Ce oxides impregnated granular activated carbons (MnCe-ACs) with ozone process (MnCe-AC/O 3 ) are developed in this research for the treatment of landfill leachate. Most of the landfills fail to meet the COD discharge limit (200 mg/L) in Taiwan due to the high contents of humic acids (HAs) in leachates. Experimental results indicate that MnCe-AC/O 3 processes could effectively remove HA, COD and TOC from landfill leachate. Parameters affecting the HAs removal efficiencies, such as types of MnCe-AC, pH, Cu(II), salts and t -butanol are investigated. In general, the removal efficiencies are in the order of MnCe-AC/O 3 > GAC/O 3 > O 3 > MnCe-AC > GAC. MnCe-AC can be used for at least four cycles without significant reduction in performance. The main removal mechanisms of HAs by the MnCe-AC/O 3 processes involved hydroxyl radicals based on the addition of t -butanol experiments. Liquid film diffusion model is the best fitted model for the MnCe-AC/O 3 process. In conclusion, the MnCe-AC/O 3 process can effectively remove organic compounds in landfill leachate to meet the requirement of COD discharge limit with minimal amount of sludge production.

The use of isotopically enriched tin tracers to follow the transformation of organotin compounds in landfill leachate

Landfill leachates are an important pool of organotin compounds (OTCs). Several studies have been performed on the occurrence of OTCs in landfill leachates, but only a few of them report degradation and biomethylation processes by bacteria. In the present study transformation of OTCs in landfill leachate was investigated under simulated landfill conditions over a time span of six months. The degradation and biomethylation processes of OTCs were followed by the use of isotopically enriched tin tracers, namely 117Sn-enriched tributyltin (TBT), 119Sn-enriched dibutyltin (DBT), 117Sn-enriched SnCl2, 117Sn-enriched SnCl4 and a 119Sn-enriched butyltin mix containing TBT, DBT and monobutyltin (MBT). Transformation of OTCs in spiked leachates was followed at m/z of the enriched spikes and at m/z 120, which allowed simultaneous observation of the transformation of OTCs in the leachate itself and of the added spike. In parallel, these processes were also monitored in a non-spiked leachate sample at m/z 120. Quantification of OTCs was performed by gas chromatography – inductively coupled plasma mass spectrometry (GC-ICP-MS). To discriminate the biotic and abiotic transformations of OTCs and inorganic tin species, sterilization of leachate was also performed and data compared to non-sterilized samples. During the course of the experiment the microbial degradation of TBT was clearly manifested in Sn-enriched spiked leachate samples, while abiotic pathway of degradation was observed for DBT. Biomethylation process was also observed in the leachate spiked with Sn-enriched Sn2+ or Sn4+, in concentrations close to those found for total tin in landfill leachates. Monomethyltin (MMeT) was formed first. Stepwise alkylation resulted in dimethyltin (DMeT) and trimethyltin (TMeT) species formation. Hydrolysis of Sn2+ and Sn4+ species was found to be a limiting factor which controlled the extent of methyltin formation. The results of the present investigation importantly contribute to a better understanding of the processes that OTCs undergo in leachates, and provide useful information to managers of landfills in taking measures necessary to prevent the release of toxic methyltin species to the nearby environment.