Denitrification capacity of a landfilled refuse in response to the variations of COD/NO3--N in the injected leachate

► Six-year-old landfilled refuse had high denitrification capacity. ► Nitrate reduction rate increased with the increasing COD loading. ► Primary denitrifier shifts from autotrophic to heterotrophic with the increasing COD/NO3--N ratios. ► The biodegradable COD/NO3--N ratio should be higher than 6.0 for rapid denitrification.