Influence of influent pH value on nitrite accumulation in a biological aerated filter (BAF)

Influence of the pH value of influent on the nitrite accumulation was investigated in a biological aerated filter (BAF) operated in normal conditions. The removal efficiency of ammonia nitrogen and the performance of nitrite accumulation in the BAF were also discussed. The results showed that the ammonia nitrogen removal in BAF was heavily influenced by the influent pH value. Drastically fluctuating of the influent pH value was not conducive to the removal of ammonia nitrogen but beneficial to the nitrogen accumulation. It was found that the continuous rising of pH value could hinder the activity of ammonia oxidizing bacteria to adapt alkaline environment, and there were approximately 77.2% and 88% of ammonia nitrogen were removed in the middle and the upper part of filter bed respectively. It was considered that the nitrite accumulation could be induced in BAF by simply adjusting the influent pH value, but the situation of a long-term and stable formation of nitrite accumulation would get out of hand, at the same time, the removal efficiency of ammonia nitrogen would not high and unstable.