Removal of Organics and Nitrogen from Municipal Landfill Leachate in Two-Stage SBR Reactors

The aim of this study was to investigate efficiency of ammonium nitrogen removal from municipal landfill leachate in activated sludge in two-stage SBR reactors. Treated leachate contains low concentrations of organic substances measured as chemical oxygen demand (COD) − 757 mg O2/dm 3 and high concentrations of ammonium − 362 mgNNH4/dm 3. Nitrification was studied in two parallel, aerated SBR reactors with two different hydraulic retention times (HRT), 3 and 2 days, respectively. We have found that 2 days HRT was sufficient to achieve complete nitrification. In the effluent ammonium, nitrite and nitrate nitrogen concentrations were 0.08 mgNNH4/dm 3, 0.04 mgNNO2/dm 3 and 320 mgNNO3/dm 3, respectively. The ammonium nitrogen removal rate was 20.2 mgNNH4/dm 3.h. The effluent from aerobic reactors (HRT 2 days) was fed to the anoxic SBR reactors. An external carbon source (methanol) was added to promote denitrification. In the anoxic reactor, at a methanol dosage 3.6 mg COD/mg NNO3 and HRT of 1 day complete denitrification was achieve with nitrate nitrogen residual concentrations of 0.9 mgNNO3/dm 3. The maximum denitrification rate was 48.4 mgNNOx/dm 3.h. The highest values of the yield methanol coefficient Ym/N-NOx were determined for dosages 3.6 mg COD/mg NNO3 and 5.4 mg COD/mg NNO3,, the lowest for 1.8 mg COD/mg NNO3.