Leachate Research Articles

Assessment of leachate potential contamination of municipal landfill using leachate pollution index and multivariate statistical analysis based on seasonal variations

Sanitary landfills offer a convenient and cost-effective way to dispose of MSW waste. The breakdown of waste in landfills generates highly poisonous leachate. This liquid can disperse and percolate through the soil, potentially polluting the surrounding water bodies; minimizing the environmental damage caused by leachate lies in thoroughly understanding its unique characteristics at each landfill site. The present study evaluates the leachate's physio-chemical characteristics from municipal landfills and adjacent groundwater sources. To evaluate the impact of temporal seasonal fluctuation, leachate and water samples were collected in three distinct seasons such as pre-monsoon (Pre-M), monsoon (In-M), and post-monsoon (Post-M). The analysis revealed a seasonal variation in pollution levels in the leachate sample, as evidenced by the high Leachate Pollution Index (LPI) spanning 27.121–17.396. Water samples collected across three seasons yielded Water Quality Index (WQI) values ranging from 55.59 to 279.64, with the Pre-M season exhibiting the highest level of water quality. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis were employed to understand the elemental composition further. The presence of heavy metals Zn, Cr, Cu, Ni, Fe, Si, and Hg was determined combined through the Inductive Coupled Plasma Atomic Emission Spectroscopy technique and EDX. The correlation matrix heat map helped to reveal the interconnection between different leachate parameters, and dendrogram clusters revealed the relation between the six sampling points. At the same time, Principal component analysis was performed to simplify the complex data set and determine the predominance of pollutants over the sample points. As explored in this study, understanding the contamination potential of landfill leachate is crucial for developing strategies before its disposal to mitigate its impact.

Methanogenesis kinetics of organic matter of the leachate in an up-flow anaerobic sludge blanket reactor

Understanding the treatment of leachate mediated by the development of anaerobic sludge makes it possible to create an effective design process of biodegradation technology. This study used an up-flow anaerobic sludge blanket (UASB) reactor equipped with a gas–liquid-solid separator to capture CH4 for treating landfill leachate to improve understanding of methanogenesis kinetics of organic matter. The performance of UASB was able to remove 154.75 g/L of chemical oxygen demand (COD) content of the leachate originally anticipated to emit 2.99 L of CH4 production into the atmosphere. The trend in the variation of internal mass transfer (IMT) factor was close to the global mass transfer factor; however, it was far higher than that of external mass transfer (EMT) factor. After 30 days of the experiment, methanogenesis kinetics of organic matter of the leachate were supported mainly by the breakdown of complex molecules. The rate-limiting step of CH4 desorption was controlled by IMT at the beginning and then by EMT after 30 days of the experiment. The strongly decreased EMT factor was counterbalanced by an increased value of the IMT factor at before 5 days of the experiment. It would be of interest to predict the methanogenesis kinetics of CH4 desorption using the Generalized Fulazzaky equations, which cannot be evaluated using other models. Analysis of the methanogenesis kinetics of organic matter of the leachate provides a new insight into the performance of UASB reactor, which may contribute to advanced treatment of landfill leachate in the future.

Biotransformation of 6:2/4:2 fluorotelomer alcohols by Dietzia aurantiaca J3: Enzymes and proteomics

Per- and polyfluoroalkyl substances (PFAS) are recalcitrant synthetic organohalides known to negatively impact human health. Short-chain fluorotelomer alcohols are considered the precursor of various perfluorocarboxylic acids (PFCAs) in the environment. Their ongoing production and widespread detection motivate investigations of their biological transformation. Dietzia aurantiaca strain J3 was isolated from PFAS-contaminated landfill leachate using 6:2 fluorotelomer sulphonate (6:2 FTS) as a sulphur source. Resting cell experiments were used to test if strain J3 could transform fluorotelomer alcohols (6:2 and 4:2 FTOH). Strain J3 transformed fluorotelomer alcohols into PFCAs, polyfluorocarboxylic acids and transient intermediates. Over 6 days, 80 % and 58 % of 6:2 FTOH (0.1 mM) and 4:2 FTOH (0.12 mM) were degraded with 6.4 % and 14 % fluoride recovery respectively. Fluorotelomer unsaturated carboxylic acid (6:2 FTUCA) was the most abundant metabolite, accounting for 21 to 30 mol% of 6:2 FTOH (0.015 mM) applied on day zero. Glutathione (GSH) conjugates of 6:2/4:2 FTOH and 5:3 FTCA adducts were also structurally identified. Proteomics studies conducted to identify enzymes in the biotransformation pathway have revealed the role of various enzymes involved in β oxidation. This is the first report of 6:2/4:2 FTOH glutathione conjugates and 5:3 FTCA adducts in prokaryotes, and the first study to explore the biotransformation of 4:2 FTOH by pure bacterial strain.

Optimization of Ammonia Removal from Landfill Leachate by Aeration Using Response Surface Methodology (RSM)

Landfill leachate has a high concentration of ammonia, making it a harmful pollutant for both surface and groundwater. One of the most favoured methods for removing ammonia from leachate is aeration, as it has been proven to remove a significant amount of ammonia in the most efficient and economical way. The effect of operational variables on ammonia removal efficiency by aeration was investigated in the current study by applying Response Surface Methodology (RSM) approach. Three operating parameters such as airflow rate, aeration time and lime dosage were investigated to achieve the optimization of ammonia removal. The optimal parameters for a favourable reaction of ammonia-nitrogen (NH3N) removal were found to be 6 L/min airflow, 90 minutes aeration time, and a lime dosage of 6 g/L. At these ideal conditions, Quadratic RSM predicted a maximum NH3N removal of 98.0%, which has been validated by the experiment and successfully removed 97.6%. The finding also showed that airflow rate and aeration time were more significant than lime dosage for NH3N removal. Due to increased contact time between air and liquid, regardless of the amount of lime used, increasing the aeration period ammonia removal efficiency. Considering the influential factors, determining the optimum condition for ammonia removal by aeration will explain the potential interferences that may inhibit the efficient recovery of NH3N. Hence, aeration is a promising approach for ammonia removal from landfill leachate.

Removal of Ammonia and Colour from Landfill Leachate using Integrated Electrocoagulation-Zeolite Adsorption Processes

The amount of waste generated in Malaysia had increased annually due to both economic and population accelerations. This resulted in an increase in leachate production that contains a high amount of ammonia nitrogen (NH3-N) and colour, which is a severe problem for both environments as well as for human health. Therefore, this study aimed to determine the potential of Electrocoagulation (EC) – zeolite adsorption for removing NH3-N and colour from landfill leachate. In the experimental works, two batch studies consist of batch EC using aluminium (Al) cylindrical electrode and batch adsorption study using clinoptilolite zeolites adsorbent were conducted using leachate sample collected from Pulau Burung Sanitary Landfill (PBSL). The batch EC experiment was carried out to determine the optimum removal of NH3-N and colour by the effect of current density (7 - 35 mA/mm2), initial pH (5 - 9), electrolysis time (0 - 90 minutes) and inter-electrode distance (5 - 25 mm). An integrated EC - zeolite adsorption was carried out under the optimum condition of 2.0 g/150 mL adsorbent dosage, contact time of 100 minutes and an initial pH value of 8. Based on the experiment, almost 50% of NH3-N and 95% of colour were removed using a single EC under the optimum current density of 14.0 mA/mm2, pH 5, electrolysis time of 75 minutes and 15 mm of inter-electrode distance. A comparison of colour removal between single EC and EC-Zeolite showed the same degradation performance. The interaction of hydrogen ion (H+) with aluminium hydroxide ion (Al (OH)3) produces during EC stabilises small particles forming larger sludge that reduces colour concentration. The removal of NH3-N increased from 50.0% to 93% when EC was integrated with clinoptilolite zeolite adsorption. In conclusion, the results show that both processes can potentially remove colour while the integrated process effectively removes NH3-N from landfill leachate. The proposed treatment helps optimise process performance while minimising the operational cost of the treatment. Thus, the proposed integrated EC – zeolite adsorption processes can be an alternative to landfill leachate treatment which aligns with the 12thMalaysia Plan to reduce pollution and carbon emissions to become a carbon neutral nation as early as 2050.

Optimization of Ammonia Removal from Landfill Leachate by Aeration Using Response Surface Methodology (RSM)

Landfill leachate has a high concentration of ammonia, making it a harmful pollutant for both surface and groundwater. One of the most favoured methods for removing ammonia from leachate is aeration, as it has been proven to remove a significant amount of ammonia in the most efficient and economical way. The effect of operational variables on ammonia removal efficiency by aeration was investigated in the current study by applying Response Surface Methodology (RSM) approach. Three operating parameters such as airflow rate, aeration time and lime dosage were investigated to achieve the optimization of ammonia removal. The optimal parameters for a favourable reaction of ammonia-nitrogen (NH3N) removal were found to be 6 L/min airflow, 90 minutes aeration time, and a lime dosage of 6 g/L. At these ideal conditions, Quadratic RSM predicted a maximum NH3N removal of 98.0%, which has been validated by the experiment and successfully removed 97.6%. The finding also showed that airflow rate and aeration time were more significant than lime dosage for NH3N removal. Due to increased contact time between air and liquid, regardless of the amount of lime used, increasing the aeration period ammonia removal efficiency. Considering the influential factors, determining the optimum condition for ammonia removal by aeration will explain the potential interferences that may inhibit the efficient recovery of NH3N. Hence, aeration is a promising approach for ammonia removal from landfill leachate.

Pollutant degradation and hydrogen production of landfill leachate membrane concentrates via aqueous phase reforming

Membrane filtration is a mainstream method for landfill leachate treatment, leaving the landfill leachate membrane concentrates (LLMCs) a high-toxicity residue. Conventional LLMCs disposal technology shows specific challenges due to the low biodegradability, high inorganic salts, and high heavy metal ions content of LLMCs. Therefore, it is necessary to degrade LLMCs with a more suitable technology. In this study, a special method was proposed to convert some organic chemicals into valuable compounds by aqueous phase reforming (APR). Ni-based catalysts (Ni//La2O3, Ni/CeO2, Ni/MgO, and Ni/Al2O3) were prepared to investigate the effect of different supports on the APR of LLMCs. APR performed outstanding characteristics in the decrease of chemical oxygen demand (COD) and total organic carbon (TOC), the degradation of macromolecules, and the removal of heavy metal ions in the aqueous phase. In addition, H2 was generated which is beneficial for energy compensating during the APR process. The best-performing catalyst (Ni/Al2O3) was selected to investigate the effects of reaction temperature, reaction time, and catalyst addition on product distribution. The optimal H2 selectivity (44.71%) and H2 production (11.63 mmol/g COD) were obtained at 250 °C with 2 g Ni/Al2O3 usage for 1 h. This paper provided a new perspective on the disposal of LLMCs, which will degrade pollutants efficiently.

Rejuvenated end-of-life reverse osmosis membranes for landfill leachate treatment and reuse water reclamation

Landfills remain a prevalent method for municipal solid waste disposal, yet concerns persist regarding leachate generation and its environmental impact. This research paper investigates the reuse of end-of-life reverse osmosis membranes for treating landfill leachate (LL) after their rejuvenation. The rejuvenation process involved a specific chemical cleaning procedure that allows for permeability recovery without compromising the membrane rejection capacity when compared to o pristine reverse osmosis. It was also explored the hypothesis how previous membrane use affects the rejuvenation process by considering end-of-life membranes used for desalination of brackish water and treated water. While both could be effectively rejuvenated, those used for brackish desalination were more susceptible to irreversible fouling. In such cases, recycling the membrane and converting it to porous ultrafiltration or microfiltration membranes is recommended. For membranes previously used for treated water desalination, it was observed high efficiency in LL treatment across multiple filtration cycles. The average flux for these membranes corresponded to 6.9 ± 0.4 L/m2h (operating pressure: 10 bar), and the rejection were greater than 89.4 % for chemical oxygen demand and 98.6 % for color. In complement, it was investigated the contribution of pretreatment with ultrafiltration membranes. Ultrafiltration was effective in preventing membrane fouling and improving the physicochemical quality of reclaimed water from landfill leachate. Overall, this research provides valuable insights into the potential reuse of end-of-life reverse osmosis membranes from treated water desalination plant for LL treatment, contributing to sustainable waste management and wastewater treatment solutions.

Microalgal production and nutrient recovery under mixotrophic mode using cheese whey permeate

Mixotrophic microalgal solutions are efficient nutrient recovery methods, with potential to prolong the cultivation seasons in temperate climates. To improve operation sustainability, the study used landfill leachate for nitrogen source and whey permeate for phosphorus and organic carbon. A non-axenic polyculture, dominated by green algae, was cultivated in mixotrophic mode on glucose or whey permeate compared to a photoautotrophic control in outdoor pilot-scaled raceway ponds during Nordic spring and autumn. The whey permeate treatment had the highest algal growth rate and productivity (0.48 d−1, 183.8 mg L−1 d−1), nutrient removal (total nitrogen: 21.71 mg L−1 d−1, total phosphorus: 3.05 mg L−1 d−1) and recovery rate (carbon: 85.19 mg L−1 d−1, nitrogen: 17.01 mg L−1 d−1, phosphorus: 2.58 mg L−1 d−1). When grown in whey permeate, algal cultures demonstrated consistent productivity and biochemical composition in high (spring) and low light conditions (autumn), suggesting the feasibility of year-round production in Nordic conditions.

Molecular Response of Dissolved Organic Matter in Aquifer to Landfill Leachate Leakage

Molecular Response of Dissolved Organic Matter in Aquifer to Landfill Leachate Leakage

Versatile enhancement for anaerobic moving bed biofilm (AnMBBR) treating pretreated landfill leachate by hydrochar: Energy recovery, greenhouse gas emission reduction and underlying microbial mechanisms

Hydrochars were prepared from fruit peels (HC-1) and vegetable waste (HC-2), and combined with fiber spheres, respectively, to form homogeneous biocompatible carriers, which were used for anaerobic moving bed biofilm reactor (AnMBBR) to enhance anaerobic digestion (AD) performance and energy recovery of landfill leachate treatment. Compared with the control AnMBBR with conventional fiber spheres as carriers, the chemical oxygen demand (COD) removal efficiency of the AnMBBR with HC-2 increased from 75 % to 88 %, methane yield increased from 77.7 mL/g-COD to 155.3 mL/g-COD, and achieved greenhouse gases (GHG) emission reductions of 1.74 t CO2 eq/a during long-term operation. HC-2-fiber sphere biocarriers provided more sites for attached-growth biomass (AGBS) and significantly enhanced the abundance of functional microbial community, with the relative abundance of methanogenic bacteria Methanothrix increased from 0.03 % to over 24.4 %. Moreover, the gene abundance of most the key enzymes encoding the hydrolysis, acidogenesis and methanogenesis pathways were up-regulated with the assistance of HC-2. Consequently, hydrochar-assisted AnMBBR were effective to enhance methanogenesis performance, energy recovery and carbon reduction for high-strength landfill leachate treatment.

Unlocking the application potential of superabsorbent polymers in landfill leachate treatment

The leachate generation is an inevitable consequence of landfill disposal, and thus it is critically important to acquire effective approach to preventing contamination of the underlying soils and groundwater aquifers. Currently, there is no consensus on the best approach; the biological treatment and the membrane technology are widely tested but each has its own drawbacks. On the other hand, superabsorbent polymers are nowadays widely used in many liquid-absorbing applications but have rarely been assessed for the application of landfill leachate treatment. In this study, a comprehensive analysis of the physicochemical parameters, ionic parameters, and trace elements of the collected leachate was carried out, and four commercially available superabsorbent polymers with different chemical compositions were tested in respect of their kinetics of adsorption and desorption, both load-free and under-load, in deionized water, tap water, and leachate, respectively. The results are of significant importance in elucidating the application potential of commercially available superabsorbent polymers in landfill leachate treatment.

Scenedesmus sp. as a phycoremediation agent for heavy metal removal from landfill leachate in a comparative study: batch, continuous, and membrane bioreactor (MBR).

Improper disposal of municipal solid waste led to the release of heavy metals into the environment through leachate accumulation, causing a range of health and environmental problems. Phycoremediation, using microalgae to remove heavy metals from contaminated water, was investigated as a promising alternative to traditional remediation methods. This study explored the potential of Scenedesmus sp. as a phycoremediation agent for heavy metal removal from landfill leachate. The study was conducted in batch, continuous, and membrane bioreactor (MBR). In the batch system, Scenedesmus sp. was added to the leachate and incubated for 15days before the biomass was separated from the suspension. In the continuous system, Scenedesmus sp. was cultured in a flow-through system, and the leachate was continuously fed into the system with flow rates measured at 120, 150, and 180mL/h for 27days. The MBR system was similar to the continuous system, but it incorporated a membrane filtration step to remove suspended solids from the treated water. The peristaltic pump was calibrated to operate at five different flow rates: 0.24 L/h, 0.30 L/h, 0.36 L/h, 0.42 L/h, and 0.48 L/h for the MBR system and ran for 24h. The results showed that Scenedesmus sp. was effective in removing heavy metals such as lead (Pb), cobalt (Co), chromium (Cr), nickel (Ni), and zinc (Zn) from landfill leachate in all three systems. The highest removal efficiency was observed for Ni, with a removal of 0.083mg/L in the MBR and 0.068mg/L in batch mode. The lowest removal efficiency was observed for Zn, with a removal of 0.032mg/L in the MBR, 0.027mg/L in continuous mode, and 0.022mg/L in batch mode. The findings depicted that the adsorption capacity varied among the studied metal ions, with the highest capacity observed for Ni (II) and the lowest for Zn (II), reflecting differences in metal speciation, surface charge interactions, and affinity for the adsorbent material. These factors influenced the adsorption process and resulted in varying adsorption capacities for different metal ions. The study also evaluated the biomass growth of Scenedesmus sp. and found that it was significantly influenced by the initial metal concentration in the leachate. The results of this study suggest that Scenedesmus sp. can be used as an effective phycoremediation agent for removing heavy metals from landfill leachate.

Pretreatment for potable reuse: Enhancing the biological removal of 1,4-dioxane from landfill leachate through cometabolism with tetrahydrofuran.

1,4-Dioxane is a probable human carcinogen and a persistent aquatic contaminant. Cometabolic biodegradation of 1,4-dioxane is a promising low-cost and effective treatment technology; however, further demonstration is needed for treating landfill leachate. This technology was tested in two full-scale moving bed biofilm reactors (MBBRs) treating raw landfill leachate with tetrahydrofuran selected as the cometabolite. The raw leachate contained on average 82 μg/L of 1,4-dioxane and before testing the MBBRs removed an average of 38% and 42% of 1,4-dioxane, respectively. First, tetrahydrofuran was added to MBBR 1, and 1,4-dioxane removal was improved to an average of 73%, with the control MBBR removing an average of 37% of 1,4-dioxane. During this period, an optimal dose of 2mg/L of tetrahydrofuran was identified. Tetrahydrofuran was then fed to both MBBRs, where the 1,4-dioxane removal was on average 73% and 80%. Cometabolic treatment at the landfill significantly reduced the concentration of 1,4-dioxane received from the landfill at a downstream wastewater treatment and indirect potable reuse facility, reducing the load of 1,4-dioxane from 44% to 24% after the study. PRACTITIONER POINTS: Cometabolic degradation of leachate 1,4-dioxane with THF in MBBRs is a feasible treatment technology and a low-cost technique when retrofitting existing biological treatment facilities. The MBBRs can be operated at a range of temperatures, require no operational changes beyond THF addition, and operate best at a mass ratio of THF to 1,4-dioxane of 24. Source control of 1,4-dioxane significantly reduces the concentration of 1,4-dioxane in downstream wastewater treatment plants and potable reuse facilities.

Transfer of Metals from the Soil to <i>Medicago sativa</i> Irrigated with Municipal Landfill Leachate

Transfer of Metals from the Soil to <i>Medicago sativa</i> Irrigated with Municipal Landfill Leachate

Integration of Geophysical and Hydrochemical Methods to Determine the Groundwater Contamination in Al-Hosayniat Landfill South East Mafraq City, Jordan

An integration of Geophysical – Electromagnetic and hydro-chemical methods was used to investigate the potential of groundwater contamination due to Al-Hosayniat Municipal Landfill (HL) southeast of Mafraq city. Twenty-five Time Domain Electromagnetic (TDEM) soundings were carried out inside and outside the HL in addition to one WNW-ESE Very Low Frequency (VLF) profile. The TDEM's results help to define the subsurface geology and structures down to 240m depth. The results also depict the presence of a major fault striking NW-SE that crosses the whole landfill, this fault is documented in the surface geological map, and it was delineated and imaged by TDEM measurements and detected at larger depths. VLF results also detected the presence of a major fault beneath the landfill. The presence of the fault just beneath the HL may enhance the leachate movement which can imply groundwater contamination hazards for a longer period as it is a preferential pathway for contaminants. The results of water quality analyses of adjacent wells show higher concentrations of Na+, SO-24, TDS in some wells and this can be ascribed to agricultural activities and over-pumping in the area rather than landfill leachate. The heavy metal concentrations were found to be within the permissible limits and did't indicate direct contamination due to the HL. However, Fluorite (F-) shows a high concentration of (1.3mg/l) in WS4 and WS5 wells and approaches the permissible limit (1.5mg/l) according to the Jordan Water Standards (JWS). Bromide (Br) shows high concentration of (0.6mg/l) in well Al-2462.

Bioremediation of Nitrate and Nitrite on the Rehabilitation of Contaminated Jatibarang Landfill and the Application of Calla Lily

Currently, waste processing is a problem because it is not yet optimal. The high content of nitrates and nitrites results in environmental pollution which can cause losses because it affects health and biodiversity. One effort to control environmental pollution is phytoremediation using calla lily (Zantedeschia aethiopica) to remediate nitrate and nitrite levels that do not comply with quality standards so that pollution can be minimized. This research aims to determine the effectiveness of calla lily as a phytoremediation agent for landfill leachate nitrate and nitrite. This experimental research method uses a Completely Randomized Design (CRD) which consists of three treatment levels, namely variations in calla lily biomass of 0 grams, 200 grams, and 400 grams with 3 repetitions, and measurements of nitrate and nitrite levels are carried out on day 1, day 2. 3, and 7. The results showed that the most optimal percentage reduction in leachate nitrate levels occurred in the P1 on the day 7, namely 45%, while the most optimal percentage reduction in leachate nitrite levels occurred in the P1 on the day 7, it was 53%. The final nitrate content after the research was in accordance with the quality standards of PP RI No.22 of 2021, while the leachate nitrite content after treatment still exceeded the quality standards of PP RI No.22 of 2021. Calla lily has the potential to reduce nitrate and nitrite levels due to landfill leachate pollution.

Comprehensive Assessment of the Relationship between Metal Contamination Distribution and Human Health Risk: Case Study of Groundwater in Marituba Landfill, Pará, Brazil

Effective management of urban solid waste in the Metropolitan Region of Belém, State of Pará, Brazil is essential for conserving ecosystems and public health in eight cities, emphasizing the municipality of Marituba. Considering the vulnerability of underground water resources in Marituba to pollution due to the possible impact of leachate percolation from the landfill, this study evaluates the quality of groundwater captured in tubular wells from different adjacent locations potentially used for human consumption. For this purpose, the systematic methodologies of the groundwater quality index and human health risk assessment analysis: non-carcinogenic and carcinogenic risk to human health were used based on chronic daily intake of heavy metals by consumption and dermal adsorption of groundwater, measured through risk quotients, risk index, and incremental lifetime cancer risk. To evaluate the interrelationships of pollutants, analysis of variance, hierarchical cluster analysis, and principal component analysis were used based on the spatio-temporal quantification of pH, temperature, electrical conductivity, As, Al, Ba, Co, Cd, Cu, Cr, Fe, Hg, Ni, Pb, Sb, Se, U, and Zn. Residents of the study area are not at potential risk, as the results demonstrate that groundwater is within the potability standards of Brazilian legislation, except for aluminum concentrations, which ranged from 53.12 to 378.01 μg L−1 and 3.82 to 339.5 μg L−1 in the dry and rainy seasons, respectively, exceeding the established limit of 200.0 μg L−1. The quality index for groundwater and the heavy metal pollution index demonstrated that groundwater has good drinking quality with low metal contamination. The risk was considered low at all sampling sites in the non-carcinogenic risk assessment. Principal component analysis indicated that the sources of metal pollution are natural origins and anthropogeny. In this sense, they become worried because aluminum is a recognized neurotoxicant that can interfere with the central nervous system’s critical physiological and biochemical processes. Furthermore, despite complying with potability standards, trace concentrations of highly toxic metals such as As, Pb, Cd, and Ni may indicate initial contamination by landfill leachate.

Exploring relationships among landfill leachate parameters through multivariate analysis for monitoring purposes.

Elucidating the properties of landfill leachate and the relationships among leachate parameters is crucial for efforts to determine appropriate landfill leachate monitoring activity and management strategies. This study investigated the physical, chemical and optical parameters of leachate in an old Japanese landfill over a 13-month period. The parameters were explored based on their relationships with the maximum fluorescence (Fmax) of three components (microbial humic-like C1, terrestrial humic-like C2 and protein-like C3) deconvoluted from excitation-emission matrix fluorescence spectroscopy coupled with parallel factor analysis. Dissolved organic carbon (DOC), chemical oxygen demand (COD), Cl- and SO42- concentrations and pH ranged from 2.6 to 38.2 mg C L-1, 9 to 324 mg L-1, 14 to 972 mg L-1, 26 to 1554 mg L-1 and 6.9 to 11.6, respectively. Linear regression analysis suggested that the Fmax values of C2 and C3 represented DOC, whereas the Fmax value of C2 alone could serve as a COD indicator. Hierarchical cluster analysis and principal component analysis were employed to successfully categorise leachate samples based on their locations. Higher dissolved organic matter levels were observed in leachate within the old disposal area, whereas elevated levels of inorganic components such as SO42- and Cl- were found in leachate collected from the extended disposal area and at a treatment facility. Statistical analysis provides crucial tools for assessing and managing various areas of a landfill, supporting targeted and effective waste management strategies.

Development of a floating constructed wetland for landfill leachate treatment and its potential to remove recalcitrant organic matter

The development of simple and economical treatment technologies for the removal of recalcitrant organic matter is required to achieve long-term and sustainable treatment of landfill leachates in tropical regions. In this study, we evaluated the fundamental properties required to develop the floating constructed wetland (FCW), which consists of a buoyant planting unit made of foamed glass and cattails. The results showed that foamed glass alone can be used as a planting substrate for cattails. Treatment of a synthetic landfill leachate by a lab-scale FCW demonstrated that the test system effectively and continuously removed recalcitrant organic matter, whereas the control system did not. This removal by FCW was shown to proceed through nearly equal contributions from adsorption and potential biological processes. Furthermore, the effect of introducing an FCW in an actual waste landfill site in Thailand was simulated using the parameters obtained from this study. The simulation indicated that the introduction of the FCW into the stabilisation pond was effective in reducing both leachate volume and recalcitrant organic matter. It is important to determine how much of the stabilisation pond should be covered with the FCW for cost-effectiveness. The FCW is expected to contribute to improving long-term, sustainable, and appropriate management of landfill leachate in tropical developing countries.