been reviewed in an article published in Critical Reviews in Environmental Science and Technology journal. A possible ecological threat for the aquatic environment due to the occurrence of organic micropollutants in raw and treated landfill leachates has also been reported. Problems and failures with collection systems Leachate collection systems can experience many problems including clogging with mud or silt. Bioclogging can be exacerbated by the growth of micro-organisms in the conduit. The conditions in leachate collection systems are ideal for micro-organisms to multiply. Chemical reactions in the leachate may also cause clogging through generation of solid residues. The chemical composition of leachate can weaken pipe walls, which may then fail. Other types of leachate Leachate can also be produced from land that was contaminated by chemicals or toxic materials used in industrial activities such as factories, mines or storage sites. Composting sites in areas of high rainfall also produce leachate. Leachate is associated with stockpiled coal and with waste materials from metal ore mining and other rock extraction processes, especially those in which sulfide containing materials are exposed to air producing sulfuric acid, often with elevated metal concentrations. In the context of civil engineering (more specifically reinforced concrete design), leachate refers to the effluent of pavement wash-off (that may include melting snow and ice with salt) that permeates through the cement paste onto the surface of the steel reinforcement, thereby catalyzing its oxidation and degradation. Leachates can be genotoxic in nature. A possible risk for the aquatic environment due to the occurrence of organic micropollutants in raw or treated landfill leachates has also been reported in recent studies. References Anaerobic digestion Biodegradable waste management Environmental soil science Liquid-solid separation