Treatment of Methanogenic Landfill Leachate to Remove Ammonia Using a Rotating Biological Contactor (RBC) and a Sequencing Batch Reactor (SBR)

Abstract

The authors investigated the use of a pilot scale rotating biological contactor (RBC) and a pilot scale sequencing batch reactor (SBR) to nitrify landfill leachate with a mean ammonia nitrogen concentration of 202 mg L−1 and mean BOD5 concentration of 50 mg L−1. The research was conducted under field conditions over a 14 month period. The research showed that, for this type of leachate, the RBC ammonia removal was superior to the SBR ammonia removal. The result appeared to be due to the low solids generation potential of this type of leachate, and the impacts of low temperature on the SBR system. Mixed liquor solids concentration appeared to be the critical factor in determining SBR ammonia removal. Full ammonia removal was achieved at RBC loading rates up to 4.5 g m−2 day−1, a hydraulic retention time of 0.3 days and a temperature of 18 °C. Full ammonia removal was achieved in the SBR unit at ammonia loading rates up to 400 g m−3 day−1 (0.6 g g MLSS−1 day−1), a hydraulic retention time of 0.7 days, and 20 °C. The effect of temperature on the RBC ammonia removal was modeled using the Arrhenius Equation with Θ = 1.111 and R2 = 0.88. Ammonia was effectively removed by the RBC system at temperatures as low as 2 °C. At temperatures exceeding 20 °C, RBC performance appeared to be inhibited. Phosphorus limitation appeared to reduce RBC performance at effluent soluble PO4-P concentrations less than 0.2 mg L−1. RBC mass removal rate was affected by influent ammonia concentration. Artificially increasing the influent ammonia concentration resulted in increased ammonia removal. Neither system effectively removed BOD5, COD, colour or metals. Removal for these parameters ranged from less than 0 to 40%.