Valorizing Landfill Gas Condensate as an External Carbon Source for Denitrification in Sewage-Landfill Leachate...

Landfill gas condensate (LFGC) is an underused byproduct that could reduce the cost and environmental impact of purchased external carbon for biological nitrogen removal. This study tested LFGC as a denitrification carbon source in sequencing batch reactors (SBRs) co-treating municipal sewage and landfill leachate. Four lab-scale SBRs operated for 170 days with 98.5% sewage and 1.5% landfill leachate, supplemented with methanol, glycerin, sodium acetate, or LFGC. All reactors performed stably, achieving total nitrogen removal efficiencies of 93.1%-93.8% and effluent nitrate below 1 mg N/L. The LFGC reactor reached nitrate removal up to 99.2%, with effluent NO₃-N as low as 0.31 mg N/L. Although LFGC required more external COD (6.6 g COD/g NO₃-N removed) than the conventional carbon sources (3.6-3.7), it also enabled the shortest minimum denitrification time (2.2 h). EEM-PARAFAC and FTICR-MS analyses showed similar dissolved organic matter characteristics in all effluents, indicating that LFGC did not produce distinct fluorescent or molecular DOM signatures compared with conventional carbon sources. Overall, LFGC performed comparably to conventional liquid carbon sources while beneficially reusing a landfill byproduct.