A Review on the Fate of Emerging Contaminants in Landfill Leachate: Insights from Conventional Treatment Approaches

Landfill leachate is a dark-colored, complex liquid formed by the percolation of water through municipal solid waste, containing diverse array of emerging contaminants. Reported concentrations include pharmaceuticals such as ibuprofen (2–1,500 µg/L) and carbamazepine (up to 800 µg/L), personal care products like triclosan (50–3,200 µg/L), pesticides (50–1,200 µg/L), phthalates such as Di(2-ethylhexyl) phthalate (up to 5.3 mg/L), polycyclic aromatic hydrocarbons (20–600 µg/L), polychlorinated biphenyls (0.1–50 µg/L), per- and polyfluoroalkyl substances (up to 6,200 ng/L), microplastics (102–104 particles/L), and endocrine disruptors such as bisphenol A (0.5–1,800 µg/L). These contaminants persist in the environment, resist natural degradation, and thereby posing significant ecological and health risks. The conventional biological treatments, including activated sludge and anaerobic digestion, achieve only partial removal (20–60% for pharmaceuticals; < 30% for per- and polyfluoroalkyl substances). Physico-chemical processes such as coagulation-flocculation, advanced oxidation, and membrane filtration provide higher removal rates (60–95%) but remain energy-intensive, costly, and prone to secondary pollution. There is no single treatment that ensures complete elimination, underscoring the inadequacy of traditional methods. Recent advances, including hybrid membrane bioreactors, advanced oxidation processes, and bioelectrochemical technologies, achieve more than 90% removal of selected contaminants. The study focuses on the occurrence and fate of emerging contaminants in landfill leachate, evaluates the performance of existing treatment technologies, and compares regulatory frameworks across different countries. The insights aim to guide the development of sustainable and integrated strategies for effective leachate management.