Techniques for pollutant removal, nutrient recovery, and energy production from landfill leachates: a review

Landfill leachate is a highly polluted wastewater resulting from the decomposition of organic waste in landfills. It contains high levels of organic matter, nitrogen, phosphorus, heavy metals, and other contaminants of environmental and health concerns, but landfill leachate could also be used to produce nutrient and energy. Here we review physical, chemical, and biological methods to treat landfill leachates. Methods include adsorption, membrane separation, coagulation and flocculation, ion exchange, air stripping, chemical precipitation, electrochemical oxidation, Fenton oxidation, ozonation, photocatalysis, activated sludge process, sequential batch reactor, rotating biological contactors, nitrification and denitrification, upflow anaerobic sludge blanket, phytoremediation, and bioremediation. We discuss the technical, social, economic and environmental benefits of removing contaminants, and of recovering nutrient and energy. Physicochemical methods remove 12–95% of chemical oxygen demand, 1–100% of ammonia nitrogen, 40–96% of metals, and 44–99% of color. Advanced oxidation processes remove 19–98% of the chemical oxygen demand, 12–85% of ammonia nitrogen, and 74–98% of total organic carbon. Biological methods remove 15–93% of the chemical oxygen demand, 43–97% of the biochemical oxygen demand, 14–100% of ammonia nitrogen, and 42–98% of phosphates. Optimized leachate treatment technology can recover 10–80% of nutrients and 0.1–7 kWh/m³ of energy.