Physicochemical and Biological Processing of Municipal Landfill Leachates

Landfill leachate (leachate in the trivial sense or percolate in physics) is the residual liquid that results from the percolation of water through a waste stockpile, of which a certain fraction may be soluble. The leachate comes from the interstitial water adhered to the waste matrix and from the water (usually rainwater) that percolates into the waste mass by gravity. The viscous, colored, and very turbid liquid mass collected will constitute the landfill leachate. Its chemical and biological composition differs greatly depending on the waste deposited and changes closely with civilization and the lifestyle of a population. The considerable increase in the volumes of leachate produced at the scale of a landfill because of urban development, the increasing costs of waste management and treatment, and the effects and scarcity of fossil fuels have prompted research not only in leachate treatment but also in leachate valorization. In this chapter, we have briefly discussed the different strategies promoted and used in recent years to treat landfill leachate and the main techniques for its valorization as fertilizer to enrich agricultural soils, as a source of energy or biofuel for heating, electricity, and even as a nutrient matrix to cultivate specific organisms such as useful algae and bacteria.