ADVANCED TREATMENT OF LANDFILL LEACHATE: TOXICITY AND OPERATING COST MINIMIZATION.

Municipal landfill leachates, resulting from the percolation of water through solid waste, are considered one of the types of wastewater with the greatest environmental impact. A combination of biological and physical/chemical methods is usually required for effective treatment of medium-old age landfill leachates. Attractive potential technique are to apply chemical oxidation processes for increasing the biodegradability of recalcitrant pollutants or to employ solar-based AOPs (featured by low energy demand) as a post-treatment after a biological stage which consequently reduce the total treatment operating cost (Oller et al., 2011). In the present work the treatment of a medium-age landfill leachate was investigated by employing a sequencing batch biofilter granular reactor (SBBGR) step with or without ozone enhancement, followed or not by a polishing step with solar photo-Fenton (SphF). Objectives of the investigation were to compare different treatment strategies for optimizing the process, to achieve the lowest operating costs and to reduce the toxicity of the final effluent. These objectives were addressed for two different target COD values, namely 160 and 500 mg L-1, to be met in the final effluent for disposing of to water bodies and to sewers, respectively, requested by Italian environmental regulation. The different treatment strategies have demonstrated to be technically suitable for achieving the requested COD (160 or 500 mg L-1) and the initial toxicity reduction (using four different bioassays) goals. For the COD target of 500 mg L-1, treatment set-ups have comparable cost instead the combination SBBGR/solar photo-Fenton is economically more efficient when the target COD is 160 mg L-1