Treatment of landfill leachate containing emerging micropollutants

Abstract

Landfills of industrial and municipal solid wastes are popular methods for environmental and ecosystem protection in most of the advanced and developing countries. Nevertheless, dumping of such wastes in landfills creates serious problems particularly hazardous industrial wastes containing recalcitrant compounds. However, landfilling of hazardous industrial wastes is still the appropriate method from an economic point of view. The leachate generated from landfilling of hazardous industrial wastes is of great concern due to its toxic rich and refractory emerging micropollutants (EMs). The hazardous leachate composition is highly variable and depends on the waste composition, density, quantities, temperature, and precipitation. The leachate contains macro and micropollutants that might be potential toxic agents as well as carcinogens. The landfills are recently developed to minimize the leachate; however, recalcitrant micropollutants still are of great concern and remain the main source of pollution in nearby aquatic areas and ecosystems. This highly deteriorates the quality of surface and groundwater that subsequently causes harmful effects for human and animal health. Removal of EMs from the leachate has been a major challenge to overcome their deleterious effects and risks to the environment. Physico-chemical treatment processes such as adsorption, advanced oxidation, and non-thermal plasma are introduced. Biological treatment methods such as constructed wetlands, anaerobic degradation and membrane bioreactors (MBRs) for treatment of landfill leachate are comprehensively reviewed. Integration of MBRs with other biological technologies, that is, anaerobic/aerobic/anoxic is cost effective for degradation of EMs from the leachate. The removal efficiency of 97.4% for di-n-butyl phthalate (DBP) and 98.8% for di (2-ethylhexyl) phthalate (DEHP) was achieved in the integrated system. DBP was removed by microbial degradation and 70.1% of DEHP was eliminated due to filtration processes. The MBR removed phthalic acid esters and phenolic compounds by values of 77–96% via filtration, biodegradation, and adsorption processes. However, their efficiencies highly depend on the biomass retention time and loading of EMs. The MBR module removed alkylphenols by 60–80% and pesticides by 59–74%.