Comprehensive analysis and modeling of 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.

Characterization and biotoxicity of landfill leachate and concentrates from controlled municipal solid waste landfills

Landfill leachate and concentrates from nanofiltration (NF) and reverse osmosis (RO) processes pose potential environmental threats. This study investigates the seasonal variations in the physicochemical properties and acute toxicity of landfill leachate and concentrates from Shenyang, Liaoning, China. The hydrophilic matter (HyI) constituted the major component of dissolved organic matter (DOM) in landfill leachate (68.18% on average). Humic substances were enriched in NF and RO concentrates, accounting for 86.92 and 62.78%, respectively. Landfill leachate exhibited strong toxicity to Artemia salina, particularly in summer. Although biotreatment processes reduced toxicity, the concentrates remained toxic. Principal component analysis (PCA) revealed significant correlations between physicochemical variables and toxicity. Discriminant analysis indicated that certain variables could predict acute toxicity. This study highlights the need for effective management of landfill leachate and concentrates on mitigating environmental risks.

Variability of leachate characteristics and pollution potential in Asian disposal sites

Landfilling is a common method for disposing of municipal solid waste, but it generates landfill leachate, a significant environmental concern due to its potential ecotoxicity. Effective treatment of landfill leachate is essential to minimize environmental pollution. This study analysed 421 leachate samples from 257 disposal sites across 27 countries in Asia, examining the concentration and pollution potential of leachate pollutants in relation to site characteristics such as age, type, operational status, climatic conditions, mean annual temperature, and precipitation. The revised leachate pollution index (r-LPI) was used to quantify pollution potential, and statistical analyses were conducted to determine the influence of these factors on pollutant concentrations. The results indicated that the age of disposal sites is a significant factor, with older sites showing reduced concentrations of organic pollutants and heavy metals, while inorganic pollutant levels remained stable. Climatic conditions also significantly impacted leachate characteristics; arid regions produced more concentrated leachate with higher r-LPI values, while regions with higher rainfall produced more diluted leachate with lower r-LPI values. This study also gives the recommendation of treating leachate aiming to inform policy and regulatory frameworks for sustainable landfill management, contributing to the protection of environmental and public health.

Determination of leachate leakage around a valley type landfill and its pollution and risk on groundwater

This paper investigates leachate leakage of a typical valley-type landfill in South China and health risk of groundwater pollution. Through geophysical detection on landfill, chemical analysis of 19 parameters such as pH, total dissolved solids (TDS), total hardness (TH), potassium permanganate index (CODMn), ammonia nitrogen (NH3-N), sulfate (SO42-), chloride (Cl-), fluoride (F-), nitrate (NO3-N), nitrite (NO2-N), and heavy metals (Hg, Fe, Mn, Cu, Zn, Cr, Pb and Cd) in groundwater, and model simulation, the prediction of pollution resource and risk level is achieved. This aggregated approach aims to effectively manage and control groundwater contamination and public health risks from the source. The results of transient electromagnetic method showed that four leakage areas of impermeable layer were existed in the landfill, with an area of 336.8 m2 and a depth of 15-22 m. The chemical analysis and pollution assessment revealed that groundwater at ZK01 and ZK04 were heavily polluted, ZK02 and ZK03 were slightly polluted, and ZK05 was non-polluted. Water quality of points ZK01-04 exceeded the standard value of Class III water in the Groundwater Quality Standard (GB/T 14,848-2017), and the main excessive parameters are pH, NH3-N, Mn and Fe. The landfill leakage, rock weathering dissolution and water-rock interaction possibly were the main sources of groundwater pollution through correlation analysis (CA) and principle component analysis (PCA). Numerical simulation based on the RBCA (Risk-based Corrective Action) model thought Mn and NO3-N had adverse non-carcinogenic effects o human health risk. Assuming that no pollution control measures are taken, the average increase rate of hazard index (HI) for pollutants within the past 20 years was between 0.04 and 0.08/a, and the average expansion rates of the risk area were 341-432 m2/a. The expansion rates of risk area along the groundwater runoff were 1.6-3.8 m/a, drinking water safety downstream of main pollution source runoff is the focus of protection.

Investigation on molecular characteristics of organic compounds during a full-scale landfill leachate treatment process based on non-targeted analysis

In this study, a new methodology for evaluating full-scale landfill leachate treatment processes by non-targeted analysis using comprehensive two-dimensional gas chromatography quadrupole time-of-flight mass spectrometry (GC × GC-QTOF-MS) was proposed. The method revealed the chemical complexity of organic compounds in landfill leachate samples at the molecular level and evaluated the removal efficiency of the anaerobic-anoxic-oxic (A2O) - membrane bioreactor (MBR) - nanofiltration (NF) treatment process in conjunction with multi-level classification of organic compounds. Results showed that the results of non-targeted analysis combined with multi-level classification of organic compounds had a significant correlation with the conventional water quality parameters and can be used to evaluate the treatment process. A total of 2508 organic compounds were detected in 6 samples. 17 emerging contaminants (ECs) with known potentially hazards were detected, including Diisobutyl Phthalate (DIBP), which is toxic to male reproduction and development, and 4-Tert-Butylphenol, which causes endocrine disruption in animals. The removal rate of organic compounds by this full-scale landfill leachate treatment processes reached 79.14%. The anaerobic tank played a crucial role with 64.98% contribution. For compounds, the removal rate of heterocyclics was as high as 94.67%, and the removal rate of aliphatics was poor, only 63.49%. This treatment process had almost perfect removal effect on the steroids in alicyclics and phenols in aromatics, but poor treatment effect on saturated alkanes in aliphatics and naphthenes in alicyclics. This study provides a methodology for accurate assessment of the molecular level of treatment processes, new insights for process optimization in waste treatment plants, and data support for the detection of emerging contaminants. The environmental hazards of landfill leachate can be further evaluated in the future in conjunction with ecotoxicity assessment studies.

Effects of landfill age, climate, and size on leachate from urban waste landfills in Portugal: A statistics and machine learning analysis

The leachate generated by in urban waste landfills can cause environmental pollution if not controlled and treated. With different proportions of biodegradable waste, urban waste degrades over several phases in anaerobic conditions within a landfill. Using multivariate leachate data from 32 engineered landfills in Portugal, each with a similar waste composition, and all classified as non-hazardous waste landfills receiving urban waste, statistical inference was applied to categorise and deduce significant statistical differences in leachate volume and quality between landfill age, size, and climate, as well as the interactions and effects within these categories. The findings show that the effects of size and age on the leachate volume are prevalent over local, Mediterranean climate conditions; in larger landfills, waste may not be degrading as efficiently as in medium-sized landfills; hotter zones showed higher levels of COD and lower levels of BOD5 than warmer zones, indicating increased biological activity under higher temperature conditions; TN and NH4-N increase significantly with age and size; Cl- also significantly increases with age, showing higher levels, along with SO42-, in hotter zones as well as a concentration effect in the dry season, along with K+; heavy metals maintain levels as landfills age from intermediate to old, with only Cd2+ and Pb2+ showing significant reductions. High correlations between macro inorganics and between heavy metals were found. Cluster analysis showed two main branches, one representing the initial to intermediate stages of anaerobic degradation, and the other the interactions between leaching parameters in the later methanogenic phase of landfill stabilisation.

Physical and chemical characterization and pollution index applied in the assessment of the polluting potential of leachate from urban landfills

During the operation of the landfills, leachate should be managed with caution to avoid possible negative environmental impacts. Considering this, the present study aims to evaluate the relationship between different variables in the leachate composition and elucidate the transformation processes through which this effluent passes during the landfill's period of operation. The study was conducted with eight sanitary landfills from the state of Minas Gerais, in southeastern Brazil, and used descriptive statistical analysis, principal component analysis (PCA), correlation analysis, and calculation of the leachate pollution index (LPI). The biochemical oxygen demand (BOD5)/chemical oxygen demand (COD) ratio was between 0.20 and 0.60. We also observed a significant correlation of 0.45 between Cl- and N-NH4+, which reflects the biological degradation processes that contribute to the presence of both variables. The PCA showed that inorganic variables and organic matter dominated the first component, with coefficients above 0.65, indicating the importance of those variables in determining the general data variability. The LPI values were between 15.26 and 25.97, with BOD5, COD, and N-NH4+ having sub-indexes above 35, being the main variables that increase the pollution potential of the leachate. On the other hand, trace metals present sub-indexes below 7 due to precipitation caused by increased pH and the characteristics of the waste discarded in landfills. The study provides essential information regarding the landfill leachate characteristics and its variation over time, which can contribute to the definition of treatment technologies for this affluent in different scenarios.

Characteristics and pollution potential of leachate from municipal solid waste landfills: Practical examples from Poland and the Czech Republic and a comprehensive evaluation in a global context

The formation of leachate is mainly due to the percolating of rainwater through the body of the landfill and the physical, chemical, and biological processes taking place inside the body of the landfill. The characteristics and pollution potential of leachate from the municipal solid waste (MSW) landfills in Poland (Łubna) and the Czech Republic (Zdounky) is presented. The objectives of this study are: 1) to evaluate and compare physicochemical characteristics of leachate, 2) to demonstrate the variability of leachate parameters in time, concerning stabilization phase of the landfill, 3) to present existing relationships between the characteristics of the leachate, 4) to indicate the factors determining the variability of the leachate composition. The Leachate Pollution Index (LPI) was applied to indicate temporal changes in leachate pollution, to assess polluting ability of leachate, and to compare the pollution potential of leachate. For the Łubna landfill, the minimum, maximum, and average values of LPI were: 6.10, 39.41, and 18.44, respectively. The LPI for the Łubna landfill tends to decrease in time due to stabilization of wastes. For the Zdounky landfill, temporal decreasing of LPI was not observed. The minimum, maximum, and average values of LPI were: 6.25, 14.25, and 10.11, respectively. Alkaline characteristics of leachate from both landfills indicate the mature stage of waste storage. This phenomenon was also evidenced by the Chemical Oxygen Demand (COD), ammonium (NH₄⁺), and cadmium (Cd). For both landfills, pH was negatively correlated with most of the leachate parameters. It is the task for environmental engineers to confront existing knowledge (supplemented by the results of this work) about the properties of leachate, its changes over time and its polluting potential with the possibilities of treating and managing it properly.

A machine learning-based approach for mapping leachate contamination using geoelectrical methods

Leachate is the main source of pollution in landfills and its negative impacts continue for several years even after landfill closure. In recent years, geophysical methods are recognized as effective tools for providing an imaging of the leachate plume. However, they produce subsurface cross-sections in terms of individual physical quantities, leaving room for ambiguities on interpretation of geophysical models and uncertainties in the definition of contaminated zones. In this work, we propose a machine learning-based approach for mapping leachate contamination through an effective integration of geoelectrical tomographic data. We apply the proposed approach for the characterization of two urban landfills. For both cases, we perform a multivariate analysis on datasets consisting of electrical resistivity, chargeability and normalized chargeability (chargeability-to-resistivity ratio) data extracted from previously inverted model sections. By executing a K-Means cluster analysis, we find that the best partition of the two datasets contains ten and eleven classes, respectively. From such classes and also introducing a distance-based colour code, we get updated cross-sections and provide an easy and less ambiguous identification of the leachate accumulation zones. The latter turn out to be characterized by coordinate values of cluster centroids<3 Ωm and >27 mV/V and 11 mS/m. Our findings, also supported by borehole data for one of the investigation sites, show that the combined use of geophysical imaging and unsupervised machine learning is promising and can yield new perspectives for the characterization of leachate distribution and pollution assessment in landfills.