Abstract

Aerobic granular sludge was cultivated in three column reactors, which had been operated for 120 days under different feast/famine ratio (1:7, 1:11, 1:15). The composition of total bacteria was analyzed by testing oxygen uptake rates of mixed liquor samples taken from the reactors and calculating according to activated sludge model. The results revealed that long famine phase favored the growth of heterotrophic bacteria. The heterotrophic bacteria accounts for 49.80, 53.37, 91.39% of total bacteria respectively in R1, R2 and R3. The heterotrophic nitrification was also observed in all the reactors, which accounts for 58.62, 58.33, 61.54% of total nitrification respectively in R1, R2 and R3. A novel nitrogen-removal pathway involving simultaneous nitrification-denitrification by heterotrophic nitrification bacteria was proposed. The results revealed that microbial system consisted of heterotrophic ammonia oxidizing bacteria showed stronger capacity of simultaneous nitrification-denitrification.

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