Sanitary landfill leachate treatment using combined solar photo-Fenton and biological oxidation processes at pre-industrial scale

Abstract

This work proposes a new strategy for the treatment of leachates from sanitary landfills after lagooning pretreatment, using a solar photo-Fenton oxidation process to eliminate the most recalcitrant organic compounds, leading to a biodegradability enhancement of the leachate and promoting its subsequent oxidation in an activated sludge biological reactor. The integrated leachate treatment process was conducted in a pre-industrial plant, incorporating a photocatalytic system with 39.52 m(2) of compound parabolic collectors (CPCs) and an activated sludge biological reactor, with 3.5 m(3) capacity, operated under aerated and anoxic conditions. An extensive physico-chemical characterization of the leachate after lagooning was performed during one year, from June 2010 to May 2011, showing its high recalcitrant character mainly associated with the presence of humic substances. The efficiency of the combined treatment was evaluated concerning the leachate characteristics' variability after lagooning, availability of solar radiation during the year, and different operational process variables, such as the amount of hydrogen peroxide necessary to reach the required COD target value, biodegradability enhancement during the photo-oxidation process, iron reutilization in consecutive oxidation processes, removal of acidic sludge resulting from the acidification process and leachate temperature/average solar power. The elimination of the remaining organic carbon fraction and nitrogen compounds after the pre-oxidation step was also assessed in an activated sludge biological reactor, under aerobic and anoxic conditions, considering the composition variability of photo-treated leachate. Nitrification and denitrification rates were also evaluated.