Municipal landfill leachate is characterized by high concentrations of recalcitrant organic compounds, ammonia, suspended material and heavy metals. As a result, leachate is difficult to manage because conventional forms of biological and chemical treatment are inefficient at dealing with such a diverse and complex waste stream. Because of widely varying practices in solid waste management, an all-inclusive solution to long-term management of landfill leachate is not currently available, such that landfill managers are left with a toolbox of current practices that cannot adequately address inorganics and organics, simultaneously. This results in a major technological need for sustainable, economical options for safe discharge of leachate to the environment.
In this article, futuristic advanced oxidation processes, such as photochemical iron-mediated aeration (PIMA) and TiO2 photocatalytic oxidation are investigated. These processes are able to: 1) convert refractory organics into more biodegradable constituents, 2) remove heavy metals such as Pb, As, Cd, Hg through co-precipitation, adsorption and redox mechanisms, 3) deal with ammonia through stripping of NH3(g) and also conversion of ammonia to nitrate through aeration, 4) destroy or completely mineralize recalcitrant organics, 5) strip VOCs, 6) achieve high levels of disinfection and 7) address color/odor issues.
The Ideal Approach
As we look toward the future, the ideal leachate management approach will be sustainable, low-cost, site-specific and capable of adaptation to evolving regulations without ignoring the impacts of climate change and population growth. After evaluating 23 different engineering alternatives for long-term leachate management (Meeroff and Teegavarapu, 2010), the results indicated that the most effective and sustainable strategies for the future would involve technologies that can destroy different classes of harmful contaminants all at once, without producing adverse byproducts and residuals. One approach will be to discharge the leachate to the sanitary sewer system after onsite pretreatment, to reduce the toxicity of the leachate. The technology with the most promise includes advanced oxidation that uses the power of ultraviolet radiation from sunlight, which is free and requires no additional energy input. Two such technologies being developed at Florida Atlantic University include photochemical iron-mediated aeration (PIMA) and photocatalytic oxidation using TiO2.