Denitrification of Mature Landfill Leachate with High Nitrite in Simulated Landfill Columns Packed with Solid Digestate from Organic Fraction of Municipal Solid Waste

Purpose The management of solid digestate (SD) from organic fraction of municipal solid waste is essential component of sustainable biogas plants. Beyond land use, this study aims to evaluate the application of digestate in simulated landfill columns to enhance nitrogen conversion of partially nitrified landfill leachate (PNL). Methods Two identical simulated landfill reactors filled with SD were setup and PNL was fed through the columns. The PNL characteristics were 1004 mg N-NO2-/L, 428 mg N-NO3-/L, and 434 mg N-NH4+/L. Results After 109 days of operation, the average N-NO(2)(-)and N-NO3- removal efficiencies were 92.6% and 85.8%, respectively. The high concentrations of nitrite did not significantly inhibit methane production during denitrification in the digestate-added landfill columns as the average specific methane production yield was 20.1 normal liter (NL) CH4/kg VS. Conclusions These results suggest that the novelty of applying SD in a landfill can achieve denitrification in a carbon limited environment observed in mature landfill leachate and stabilization of the digestate.