A Critical Review on the Microbial Ecology of Landfill Leachate Treatment Systems

Abstract

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.

The leachate from the Urban Solid Waste Transfer Station produces neurotoxicity in Wistar rats

“…In this work, a significant increase in the levels of BOD demand was found. Generally, the leachate from a landfill contains a large number of organic products, heavy metals, high ammonia content and, as it matures, there is a transforming effect on the organic substances present [41] , [43] limiting free oxygen necessary to transform organic matter through aerobic microbial decomposition [28] , [8] . If leachate high in BOD is released into a body of water, it can affect aquatic life and subsequently affect water for human consumption [12] .…”

Progress in Multi-Soil-Layering Systems for Wastewater Treatment

“…Landfill leachate is also a typical type of high-strength wastewater, which has low biodegradability and a high content of COD, nitrogen, and toxic substances [50,51]. Although biological processes are commonly employed for landfill leachate treatment, the refractory organic matters and high ammonia contents are still challenging [51].…”

Synergistic Effects of Ionizing Radiation Process in the Integrated Coagulation–Sedimentation, Fenton Oxidation, and Biological Process for Treatment of Leachate Wastewater

“…Landfill leachate is a foul-smelling black or yellowish-brown liquid comprising a large amount of organic and inorganic substances, including hard-to-degrade organic substances (such as aromatic compounds and humic substances), inorganic salts (such as ammonia, carbonate, and sulfate), and metal ions (such as chromium, lead, and copper) [3]. The primary features of waste leachate include (a) a high level of organic contaminants, with chemical oxygen demand (COD) levels reaching tens of thousands of milligrams per liter, (b) it includes a range of recalcitrant and toxic contaminants, including heavy metal ions and hazardous organic compounds, and (c) a high mass concentration of ammonia nitrogen, ranging from hundreds to tens of thousands of milligrams per liter, which severely inhibits and decreases microbial activity and limits the scope of its biological treatment [4][5][6]. Because landfill leachate can contaminate ground and surface water, it is a significant public health concern, and it can have a long-term consequence on the surrounding ecosystem.…”

“…So far, several leachate treatment systems have been proposed including physicochemical and biochemical methods [9]. The conventional biological treatment systems, i.e., both aerobic and anaerobic processes, are often ineffective in dealing with the difficult-to-degrade organic matter present in landfill leachate as these processes are primarily designed for easily degradable organic matters [6,10]. This is also supported by the fact that the biochemical oxygen demand (BOD 5 ) to COD ratio of landfill leachate is ≤0.4, which falls under the category of less biodegradable compounds [11].…”