Generation mechanisms, environmental behaviors, and treatment technologies of conventional and emerging contaminants in landfill leachate: A review

The current research was carried out to evaluate improvement in the attenuative capacity of lateritic soil for landfill leachate contaminants as a result of bentonite addition. Laboratory batch adsorption test was performed using lateritic soil treated with 0%, 2.5%, 5%, 7.5% and 10% bentonite by dry weight of soil with Pb2+ and K+ ions as selected contaminants in the landfill leachate. The experimental data were analysed by both the linear and Freundlich isotherms. In this study, the untreated lateritic soil achieved about 85% and 81% removal efficiencies for K+ and Pb2+ species, respectively, while 90% and 97% removal efficiencies were achieved by lateritic soil mixed with 10% bentonite. Maximum Pb2+ adsorption capacities for soil mixtures with 0%, 2.5%, 5%, 7.5% and 10% bentonite were 1.48, 1.51, 1.55, 1.58 and 1.6 mg/g, respectively, leading to Kd values ranging from 30.04 to 77.72 mL/g, while the adsorption capacities calculated for K+ ranged from 797.68 to 907.82 mg/g with corresponding Kf values of 59.7–206.54. Correlation coefficients indicate that the adsorption data for Pb2+ were adequately described by the linear model while the adsorption equilibrium data for K+ ion fitted well to the Freundlich isotherm model. Overall, the soil mixture with higher bentonite contents produced enhanced adsorption capacities for both Pb2+ and K+ ions.

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

This chapter presents an overview of emerging contaminants in landfill leachate and their treatment methods. In addition to introducing the conventional contaminants present in the leachate, the chapter also details emerging contaminants such as poly-aromatic hydrocarbons (PAHs) and phthalate acid esters (PAEs) and their concentrations in various environmental matrices. PAHs and PAEs are highly carcinogenic, mutagenic, and teratogenic substances which is why they have attracted a lot of concern in the studies of water, air, and soil pollution. They affect the endocrinal activities in animals and humans, therefore they are known as endocrine disrupting compounds. Drawing on the treatment methods of leachate, the chapter explains physico-chemical, biological, and advanced oxidation processes. The chapter also advances the discussion on their importance and efficiency in the leachate treatment.

Technologies for the treatment of emerging contaminants in landfill leachate

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

Nowadays, the high amount of waste generated by the world population represents a major environmental problem. Landfills still represent one of the main endpoints of the solid wastes disposal in most of the countries. The major problem associated with this is the landfill leachate production. Leachate treatment using microalgae has been reported in numerous studies and it is a very promising method. A key challenge is the sensitivity of microalgae to high contaminants in landfill leachate. This paper underlines the landfill leachate treatment using Chlorella vulgaris sp. with pre-treated landfill leachate by physico-chemical treatment. Current research is to explore a dual purpose method to treat the leachate by incorporating Chlorella vulgaris sp. culturing in 100% pre-treated landfill leachate. During pre-treatment, the leachate samples were undergone coagulation process by using aluminium ammonium sulphate 12-hydrate followed by modified filtration system. The chemical analysis such as Total Solids (TS), turbidity, pH, Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Total Organic Carbon (TOC), and heavy metal contents were analysed for landfill leachate samples before the treatment, after physico-chemical treatment, and after the combined physico-chemical-biological treatment using Chlorella vulgaris. The combined coagulation, filtration and microalgae treatments achieved removal efficiencies of more than 94% on turbidity, COD, BOD, TOC, and heavy metals. Effective contaminants removal efficiencies have been attained through the pre-treatment by coagulation and filtration. Microalgae managed to polish the pre-treated leachate to achieve the standard discharge limit according to DOE of Malaysia government. The lipids with broad carbon range of (C-21 to C-36) were identified in Chlorella vulgaris. The paper proves that the deteriorative impact of landfill leachate can be reduced successfully with combined treatment approaches.

Landfill leachate, which is a complicated organic sewage water, presents substantial dangers to human health and the environment if not properly handled. Electrochemical technology has arisen as a promising strategy for effectively mitigating contaminants in landfill leachate. In this comprehensive review, we explore various theoretical and practical aspects of methods for treating landfill leachate. This exploration includes examining their performance, mechanisms, applications, associated challenges, existing issues, and potential strategies for enhancement, particularly in terms of cost-effectiveness. In addition, this critique provides a comparative investigation between these treatment approaches and the utilization of diverse kinds of microbial fuel cells (MFCs) in terms of their effectiveness in treating landfill leachate and generating power. The examination of these technologies also extends to their use in diverse global contexts, providing insights into operational parameters and regional variations. This extensive assessment serves the primary goal of assisting researchers in understanding the optimal methods for treating landfill leachate and comparing them to different types of MFCs. It offers a valuable resource for the large-scale design and implementation of processes that ensure both the safe treatment of landfill leachate and the generation of electricity. The review not only provides an overview of the current state of landfill leachate treatment but also identifies key challenges and sets the stage for future research directions, ultimately contributing to more sustainable and effective solutions in the management of this critical environmental issue.

Emerging contaminants (ECs) are compounds that recently have been shown to occur widely in the environment and identified as being a potential environmental or public health risk, but yet adequate data do not exist to determine their risk. This review article focuses on ECs including pharmaceuticals, personal care products, surfactants, plasticizers, fire retardants, pesticides and nanomaterials. Their source, fate and transport in landfill leachate and adjacent environments have been discussed. Furthermore, state-of-the-art control and treatment techniques for ECs in landfill leachate have been presented. Sustainable management efforts for screening and control of ECs have been discussed. Molecular biology techniques to enumerate microbes capable of degrading ECs in landfills and their leachate are introduced. The article also presents future perspectives on the management of ECs in landfill leachate.

Nitrate removal from landfill leachate by zerovalent iron (ZVI)

Point sources such as landfills, can release high concentrations of contaminants into the groundwater because of migration of leachate from its bottom, which is generated primarily as a result of precipitation falling on an active land- fill surface, leaching out the potential organic and inorganic contaminants from landfilled waste and discharging the same to groundwater in underlying aquifer. Leachate from young landfills has high dissolved solids content as well as a high concentration of organic matter. Landfill leachate has the potential to contaminate the surrounding environment and im- pair groundwater use. Organic contaminants in landfill leachate originate from incoming wastes or are produced as a re- sult of biochemical reactions taking place in landfills. To protect the groundwater from contamination by landfill leachate, it is quite essential to provide the bottom barrier of suitable thickness, and to minimize the amount of water that could en- ter the landfill to create leachate. The present study was undertaken to determine the rate of movement of potential con- taminants from its bottom to the aquifer media, so as to evolve a rational method for the determination of thickness of bot- tom barrier on sound engineering practice, in place of adopting a prescriptive standard, which is very common in most of the Asian countries. The study was undertaken for non conservative contaminant Dissolved Organic Carbon (DOC). The governing equation of contaminant transport was solved using finite difference method, and finite mass boundary condi- tion to ape the finite mass of contaminants in a landfill. The solution of the model was run in MatLab 7.0 for a range of Darcy velocities and retardation factors for a representative equivalent height of leachate. Design curves were drawn which can be used for determination of suitable barrier thickness on the basis of expected maximum concentration of DOC in landfill leachate and maximum permissible concentration of the same.

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

Landfill leachates are composed of a complex mixture of degradation products which include a wide range of potentially fluorescent organic molecules and compounds. Here we investigate the use of fluorescence excitation–emission matrix (EEM) analysis in detecting diffuse landfill leachate contamination in rivers. Landfill leachates from three unlined landfill sites adjacent to our study river are characterised by intense fluorescence at excitation wavelength 220–230 nm, and emission wavelength 340–370 nm, which derives from fluorescent components of the xenobiotic organic matter fraction. Seven surface water sample sites on an adjacent polluted river system were analysed for fluorescence and water quality properties. The 220–230 nm excitation wavelength, 340–370 nm emission wavelength fluorescent centre was also detected in this river system at the sample locations downstream of the landfills, but not at upstream control sites, demonstrating its use as a tracer of landfill leachate contamination. Negative correlations are observed between this fluorescence centre and dissolved oxygen in the river water samples, demonstrating the water quality implications of leachate contamination at this study site. The fluorescence intensity at the 220–230 nm excitation wavelength, 340–370 nm emission wavelength fluorescent centre in landfill leachates is such that it remains detectable at dilutions of 102–103, and the fluorescence EEM technique is rapid and cost-effective for use by river managers and water quality regulators.

Enhanced removal of COD and color from landfill leachate in a sequential bioreactor

The use of nanoparticulate zero valent iron (NZVI) in the treatment of inorganic contaminants in landfill leachate and polluted plumes has been the subject of many studies, especially in temperate, developed countries. However, NZVI's potential for reduction of chemical oxygen demand (COD) and treatment of metal ion mixtures has not been explored in detail. We investigated the efficiency of NZVI synthesized in the presence of starch, mercaptoacetic, mercaptosuccinic, or mercaptopropenoic acid for the reduction of COD, nutrients, and metal ions from landfill leachate in tropical Sri Lanka. Synthesized NZVI were characterized with X-ray diffraction (XRD), transmission electron microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), thermal gravimetric analysis, Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller. Of the samples tested, Starch-NZVI (S-NZVI) and mercaptoacetic-NZVI (MA-NZVI) performed well for treatment both COD and metal mixture. The removal percentages for COD, nitrate-nitrogen, and phosphate from S-NZVI were 50, 88, and 99 %, respectively. Heavy metal removal was higher in S-NZVI (>95 %) than others. MA-NZVI, its oxidation products, and functional groups of its coating showed the maximum removal amounts for both Cu (56.27 mg g(-1)) and Zn (28.38 mg g(-1)). All mercapto-NZVI showed well-stabilized nature under FTIR and XRD investigations. Therefore, we suggest mercapto acids as better agents to enhance the air stability for NZVI since chemically bonded thiol and carbonyl groups actively participation for stabilization process.

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