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Sanitary landfilling is still considered worldwide as one of the most common methods applied for the management of the municipal solid waste. As a consequence, vast amounts of landfill leachate are generated annually, which are characterized by variability in physicochemical composition, owing to the stabilization process that occurs over the years. However, sustainable management of landfill leachate is a challenging issue, due to diverse chemical composition and high concentration in heavy metals and xenobiotics. Despite the fact that several studies have been reported on the biotreatment of landfill leachate, only in recent years has the microbial composition in such systems have been examined. In the present review, the key role of the microbial ecology involved in depurification and detoxification of landfill leachate in activated sludge and anaerobic systems is interpreted and ecological considerations influencing landfill leachate treatment are stated. Apart from the assessment of landfill toxicity on certain model organisms, this work provides an extensive overview on microbial communities performing key biological processes during landfill leachate treatment, including nitrification-denitrification, anammox and anaerobic digestion. Moreover, microbial aspects affecting nutrient removal efficiency in such biosystems are discussed.

More and more stringent requirements for pollution control and the implementation of the new discharge standard for landfill leachate make the development and application of landfill leachate treatment a research focus. The aim of the review is to determine appropriate technique for effective treatment of landfill leachate. In the paper, various leachate treatment technologies are presented and summarized, the key control parameters and some main problems are discussed from a technological point of view. It is proposed that the improvement of existing technical and the development and industrial application of a new treatment for landfill leachate are necessary. The development and application of integrated leachate treatment process of different physical, biological and chemical technologies could be a suitable option to reduce the contamination levels of leachate. Particularly, advanced oxidation technologies and an efficient integration between physical–chemical processes and biochemical processes are indicated as a significant research direction of new technology development.

Leachate from municipal solid waste landfills poses a significant threat to aquatic ecosystems due to poor management practices. This study evaluated thirty leachate samples from Iranian metropolises using the Leachate Pollution Index (LPI). Various parameters, including BOD₅, COD, TDS, pH, EC, heavy metals, turbidity, PAHs, phthalates, and humic acid, were analysed. The BOD₅ levels ranged from 350 to 20,000 mg/L, and the COD levels ranged from 2,000 to 90,000 mg/L. The TDS content varied between 14.7 and 67 g/L, while the turbidity ranged from 15 to 186 NTU. Heavy metals were present but within standard limits. The phthalate concentrations ranged from 6 to 150.8 mg/L, and the humic acid concentrations ranged from 135 to 2,200 mg/L. Naphthalene was the most frequent hydrocarbon detected. The LPIs were less than 30 for all the samples, with the highest in Ahvaz and the lowest in the treated samples from Tehran. This study highlights the presence of persistent organic and hazardous contaminants in Iran’s municipal landfills, emphasizing the need for effective leachate treatment and improved waste management practices. Enhanced final disposal methods, increased waste recovery, and improved solid residue separation are crucial for preventing further leachate production and environmental contamination.

Dumping of solid waste in the non-engineered landfill is very common in the developing countries. Among the different disadvantages of this kind of landfilling, leachate is the major concern to public health, which is a toxic byproduct generated from the landfill; and can percolate to the ground water and consequently migrate in surface water. Using systematic review on published data, the present study endeavors to compare the leachate contamination potential of four major landfills of Bangladesh, named Amin Bazar, Matuail, Mogla Bazar and Rowfabad; which are situated in 3 of the 6 big mega cities of Bangladesh and assessed the effects of leachate leakage on surrounding water body as well as on human health. This study, for the first time calculated the leachate pollution index (LPI) for the landfill sites of Bangladesh and found that the LPI of Matuail landfill site (19.81) is much higher which is comparable to some polluted landfill sites of India and Malaysia. The concentrations of several potentially toxic metals found in the surface and ground water in the vicinity of the landfill sites were above the maximum permissible limit values of department of Environment, Bangladesh and World Health Organization (WHO). The human health risk index for toxic heavy metals in different vegetables and rice grain showed high health risk potential for Pb, Cd, Ni, and Mn. The total carcinogenic risk for Ni and Pb are found very high in the edible plants near those landfill sites, suggesting the risk of Ni and Pb induced carcinogenesis by the consumption of those plants. The present conditions of surface, ground water and agriculture products near the landfill sites of Bangladesh are much frightening to the biota and local inhabitants.

Advanced oxidation processes (AOPs) were first proposed in the 1980s for drinking water treatment and later were widely studied for treatment of different wastewaters. During the AOP treatment of wastewater, hydroxyl radicals (OH·) or sulfate radicals (SO 4 ·− ) are generated in sufficient quantity to remove refractory organic matters, traceable organic contaminants, or certain inorganic pollutants, or to increase wastewater biodegradability as a pre-treatment prior to an ensuing biological treatment. In this paper, we review the fundamental mechanisms of radical generation in different AOPs and select landfill leachate and biologically treated municipal wastewater as model wastewaters to discuss wastewater treatment with different AOPs. Generally, the treatment efficiencies rely heavily upon the selected AOP type, physical and chemical properties of target pollutants, and operating conditions. It would be noted that other mechanisms, besides hydroxyl radical or sulfate radical-based oxidation, may occur during the AOP treatment and contribute to the reduction of target pollutants. Particularly, we summarize recent advances in the AOP treatment of landfill leachate, as well as advanced oxidation of effluent organic matters (EfOM) in biologically treated secondary effluent (BTSE) for water reuse.

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

As landfilling is a common method for utilizing plastic waste at its end-of-life, it is important to present knowledge about the environmental and technical complications encountered during plastic disposal, and the formation and spread of microplastics (MPs) from landfills, to better understand the direct and indirect effects of MPs on pollution. Plastic waste around active and former landfills remains a source of MPs. The landfill output consists of leachate and gases created by combined biological, chemical, and physical processes. Thus, small particles and/or fibers, including MPs, are transported to the surroundings by air and by leachate. In this study, a special focus was given to the potential for the migration and release of toxic substances as the aging of plastic debris leads to the release of harmful volatile organic compounds via oxidative photodegradation. MPs are generally seen as the key vehicles and accumulators of non-biodegradable pollutants. Because of their small size, MPs are quickly transported over long distances throughout their surroundings. With large specific surface areas, they have the ability to absorb pollutants, and plastic monomers and additives can be leached out of MPs; thus, they can act as both vectors and carriers of pollutants in the environment.

The USA, China and India are the top three producers of municipal solid waste. The composition of solid wastes varies with income: low-to-middle-income population generates mainly organic wastes, whereas high-income population produces more waste paper, metals and glasses. Management of municipal solid waste includes recycling, incineration, waste-to-energy conversion, composting or landfilling. Landfilling for solid waste disposal is preferred in many municipalities globally. Landfill sites act as ecological reactors where wastes undergo physical, chemical and biological transformations. Hence, critical factors for sustainable landfilling are landfill liners, the thickness of the soil cover, leachate collection, landfill gas recovery and flaring facilities. Here, we review the impact of landfill conditions such as construction, geometry, weather, temperature, moisture, pH, biodegradable matter and hydrogeological parameters on the generation of landfill gases and leachate. Bioreactor landfills appear as the next-generation sanitary landfills, because they augment solid waste stabilization in a time-efficient manner, as a result of controlled recirculation of leachate and gases. We discuss volume reduction, resource recovery, valorization of dumped wastes, environmental protection and site reclamation toward urban development. We present the classifications and engineered iterations of landfills, operations, mechanisms and mining.

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

The quantity and quality of leachate generated in a landfill are very important when it comes to waste management. Sanitary landfill is still being considered as most common element for waste management. Leachate is generated in both fluctuating quantity and quality during landfilling. To eliminate the adverse effects arising from leachate and meet standards for discharge into the environment, the authorities have forced to use suitable and effective methods and technologies for leachate treatment. “Here we review (1) comprehensive information on landfill leachate (LFL) in terms of quantity, quality, and treatment methods mostly used in Iran. (2) In the present review, the treatment methods have been classified into four categories: (a) physical, (b) physicochemical, (c) biological, and (d) combined biological and physicochemical and their advantages, drawbacks, and efficiency are discussed”. Given the presence of bio-recalcitrant and refractory elements in leachate and also strict standards enacted for protection the environment, application physicochemical, as a pretreatment and biological technology seems to be a complementary option for landfill leachate treatment in Iran. However, unfortunately there are no valid information in view both points of valorization and characteristics, therefore, it can fascinate researchers to pay attention these critical parameters in LFL treatment and waste management.