Study on start-up and film formation of pre-denitrification biological aerated filter

In order to understand the start-up of pre-denitrification biological aerated filter, a lab-scale pre-denitrification BAF was built and rapid sludge draining method with gradually increasing hydraulic load start-up strategy was adopted to examine the contaminants removal efficiencies and start-up characteristics. The results showed that it took 49 days to start-up the pre-denitrificaiton BAF under the operation condition of 2.04 m³/(m²·h) of the aerobic column hydraulic load and 4.08 m³/(m²·h) of anaerobic column hydraulic load, 100% of reflux ratio and 5.6∶1 of gas-water ratio. The maturation of nitrifying bacteria in aerobic tank was the key of the start-up of pre-denitrification BAF. The maturation of denitrifying bacteria in anaerobic tank was the indication of the accomplishment of the start-up. After start-up, COD, NH₃-N and NO₃^--N in the effluent were respectively lower than 50 mg/L, 15 mg/L, 5 mg/L, which met the GB18918-2002 1A discharged standard.