Pilot-scale experience with biological nutrient removal and biomass yield reduction in a liquid-solid circulating fluidized bed bioreactor

A pilot-scale liquid-solid circulating fluidized bed (LSCFB) bioreactor was developed at the Adelaide Pollution Control Plant, London, Ontario, Canada, to study its commercial viability for biological nutrient removal. Lava rock particles of 600 μm were used as a biomass carrier media. The LSCFB removed approximately 90% organic, 80% nitrogen, and 70% phosphorus at loading rates of 4.12 kg COD/m³·d, 0.26 kg N/m³·d, and 0.052 kg P/m³·d, and an empty bed contact time of 1.5 hours. Effluent characterized by <1.0 mg NH₄-N/L, <5.0 mg NO ₃-N/L, <1.0 mg PO₄-P/L, <10 mg TN/L, <10 mg SBOD/L, and 10 to 15 mg volatile suspended solids (VSS)/L can easily meet the criteria for nonpotable reuse of treated wastewater. The system removed nutrients without using any chemicals, and the secondary clarifier removed suspended solids removal without chemicals. A significant reduction (approximately 75%) in biomass yield to 0.12 to 0.16 g VSS/g chemical oxygen demand (COD) was observed, primarily because of long biological solids retention time (SRT) of 20 to 39 days and a combination of anoxic and aerobic COD consumption.