This chapter deals exhaustively with the various techniques employed in polishing landfill leachate, the role, importance and effects of polishing leachate and the use of constructed wetlands with many examples from some countries where it has worked with considerable success. Types, forms and functions of wetlands in leachate polishing were also dealt with while the chapter also provides information on the advanced treatment wetlands technology being employed now for polishing landfill leachate; its design considerations and future projections. The role of bioremediation and aquatic plants in leachate treatment was also considered and reviewed while projected futuristic outlook of polished landfill leachate was examined.
TopIntroduction
Landfill leachate treatment has become one of the most important environmental problems due to fluctuating of composition and quantity as well as high concentrations of specific pollutants (PAH, AOX, PCB, and heavy metals) and very high ammonia nitrogen and COD concentrations (Wojciechowska et al., 2010). In the literature, considerable variations in the quality of leachate from different landfills have been reported (Kamaruddin et al., 2013; Akinbile et al., 2012a & b; Cortez et al., 2010; Sobolewski, 2007). The leachate from young landfills (where acetogenic biodegradation phase is active) is characterised by high COD, BOD as well as Na+, Cl- and NH4+ content, while the leachate produced in the subsequent methanogenic phase is characterised by relatively low COD, BOD and NH4+ content and higher pH (Jones et al., 2006; Klimiuk et al., 2007). High-tech solutions applied for leachate treatment (i.e. reverse osmosis or ozonation) are expensive and energy consuming, thus they are not suitable at many landfill sites, especially in rural areas.
Leachate treatment is one of the most difficult problems to handle, as it could be released from the start of landfill operations until potentially many decades after the closure (Christensen et al., 1992). Thus, it should be treated until they meet the environmental criteria. With natural resources being exploited at an increasing rate, as well as the threat of climate change, the concept of Sustainable Development has been given more and more attention. Sustainable Development may be broadly defined as “the principles of the current process of economic and technological development to ensure that the use of environmental resources to satisfy present demands is managed in a way that they are not left so damaged or impoverished and they cannot be used by future generations” (WCED, 2009).