A novel circulating fluidized bed-bioreactor in biological nutrient removal from municipal wastewater

The objective of this study was to examine the feasibility of a novel liquid-solid circulating fluidized bed bioreactor (LS-CFBBR) in municipal wastewater treatment. The CFBBR 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. A lab-scale CFBBR has been demonstrated to treat synthetic wastewater and degritted municipal wastewater. The CFBBR was operated at an empty bed contact time (EBCT) of 0.82 hours with and without particle recirculation. Without particle recirculation, the CFBBR was able to achieve carbon (C), total nitrogen (N) and phosphorous (P) removal efficiencies of 94%, 80% and 65% respectively, whereas with particle recirculation, 91%, 78% and 85% removals of C, N and P were achieved. The system was able to generate tertiary effluent quality characterized by BOD₅ <5 mg/L, TSS of <5 mg/L, ammonia-nitrogen <1 mg/L, total nitrogen <7 mg/L, phosphorus <1 mg/L. Combination of nitrification, denitrification and biological phosphorus removal in one unit saves space, reduces energy consumption and also produces less sludge, approximately 0.13 gVSS/gCOD, which is one-third of the conventional treatment processes.