Influence of free chlorine on nitrite accumulation in biological aerated filter(BAF)

The influence of free chlorine on the nitrite accumulation in Biological Aerated Filter (BAF) was investigated by adding chlorine in the bioreactor in order to carry out a shortcut nitrification-denitrification. The relationship of the adding dosage and feeding modes of free chlorine and the nitrite accumulation in BAF were also considered. The results show that the nitrite accumulation could be achieved by adding chlorine. When the influent concentration of chlorine was 4mg/L, the concentration of effluent nitrite nitrogen was increased remarkably after the system had been operated for 20 days, and the nitrite accumulation rate could be kept in 60%–70%. The steady state of nitrite accumulation could be maintained with decreasing in the concentration of the influent chlorine, and could also be maintained at a certain degree with the adding mode of intermittent chlorination.