Landfill leachate biological treatment using a pilot Liquid-Solid Circulating Fluidized Bed bioreactor (LSCFB)

The objective of this study was to examine the feasibility of an integrated pilot liquid-solid circulating fluidized bed bioreactor (LSCFB) in biological nutrient removal from landfill leachate treatment. Biological treatment of landfill leachate is a concern due to toxicity, high ammonia, low biodegradable organic matter concentrations, and low carbon to nitrogen ratio. The LSCFB employs attached microbial films for biodegradation of both organics and nutrients, in both soluble and particulate forms, within a single circulating fluidized bed unit. This new technology combines the more compact and efficient fixed-film process with the recently developed biological nutrient removal (BNR) process that provide the additional removal of nitrogen and phosphorous. Anoxic and aerobic columns were used to optimize carbon and nutrient removal capability from leachate using 600 μm lava rock with a total porosity of 61%, at empty bed contact times (EBCTs) of 0.55, 0.49, and 0.41 d. The LSCFB achieved COD, nitrogen, and phosphorus removal efficiencies of 85%, 80%, and 70%, respectively at a low carbon to nitrogen ratio of 3:1 and nutrients loading rates of 2.15 kg COD/(m³•d), 0.70 kg N/(m³•d), and 0.014 kg P/(m³•d), as compared with 60% □ 70% COD and 70% □ 74% nitrogen removal efficiencies achieved by upflow anaerobic sludge blanket (UASB) and moving bed bioreactor (MBBR), respectively. With particle recirculation and using degritted municipal wastewater the system was able to achieve effluent quality characterized by ≤35 mg SBOD/L, <35 mg NH ₄-N/L, <1.0 mg PO₄-P/L, and 37 mg VSS/L which can easily meet sewer by-law requirements. Remarkably low yields of 0.13, 0.15, and 0.16 g VSS/g COD were observed at a long biological solids retention times (SRTs) of 31, 38 and 44 d.