Simultaneous removal of organic matter and nitrogen compounds from landfill leachate by aerobic granular sludge

This study aimed at investigating the treatment of landfill leachate using the aerobic granular sludge process in a lab-scale sequential batch reactor (SBR-AGS). The leachate from a giant sanitary landfill localized in the State of São Paulo (Brazil) exhibited high concentration of organic matter (COD 5,300 ± 78 mg L^-1) and total nitrogen (TKN 2,630 ± 355 mg L^-1). Comparatively, the leachate was added to wastewater in three different volumetric ratios (5, 10 and 20%) and the mixtures were characterized over treatment. The results indicated that there were no significant changes in the behaviour of the biological process even at the highest leachate ratio. The granulation of the aerobic sludge occurred after 90 days of operation and the granules had a diameter of 485-1585 μm. SBR-AGS exhibited removal efficiency of 87-89% for organic matter and at least 98% for total nitrogen, regardless of the leachate ratio. The treated effluent that received 20% of leachate showed 2.7 mg L^-1 ammonia and 1.1 mg L-1 nitrate. This study shows that SBR-AGS was able to form large granules, thus promoting a simultaneous nitrification and denitrification (SND) process. We highlighted that SND occurred in low dissolved oxygen concentrations (< 1.5 mg L^-1) for 120 days, without compromising aerobic granule integrity. These results suggest that the aerobic granular sludge process is a promising alternative for the co-treatment of landfill leachate and domestic wastewater under tropical climate conditions and its use should be encouraged.