Start-up and long-term operation of the nitrification process using landfill leachates in a pilot sequencing batch bioreactor

Abstract

The elevated ammonium content found in landfill leachate make it susceptible to nitrification. The resulting nitrate or nitrite makes this effluent a viable candidate for use as a final electron acceptor in anoxic biogas biodesulfurization systems. In the present study, the long-term operation (61 weeks) of a pilot-scale reactor (1 m³) using landfill leachate as an ammonium source is presented. During stage VII (weeks 39–41) of operation, the bioreactor achieved a maximum ammonium elimination capacity of 145.0 ± 11.5 g NH₄⁺-N m⁻³ d⁻¹ (RE = 99.9 %). At these conditions, the nitrate and nitrite production were 90.2 ± 7.2 g NO₃⁻-N m⁻³ d⁻¹ and 0.6 ± 0.2 g NO₂⁻-N m⁻³ d⁻¹, respectively. The process was affected by pH sensor failures and high leachate salinity, which caused additional stress on the system. The sensitivity of biomass to increasing concentrations of landfill leachate was modeled through respirometry tests, employing the Haldane model. Maximum substrate oxidation rate values were 8.89 and 5.91 mg N gVSS⁻¹ h⁻¹ for ammonium and nitrite substrates in lab-scale respirometry tests, respectively.