Segregation of Effect between Granules and Flocs in Pn/A System Treating Acrylic Fiber Wastewater: Performance and Mechanism

Abstract

Nitrogen removal of petrochemical wastewater through partial nitritation/anammox (PN/A) is appealing, but its feasibility and stability under toxic inhibition remain unclear. In this study, a PN/A granular sludge system was started up in a membrane bioreactor and fed with diluted acrylic fiber wastewater. During long-term operation, the nitritation and anammox performance could be stable with a 30% volume ratio, further declining with increasing volume ratio resulting in deteriorated nitrogen removal. Meanwhile, the short-term inhibition batch test further showed that ammonia oxidation bacteria (AOB) in the flocs were suppressed while anammox bacteria (AnAOB) in the granules had not affected. Further analysis indicated suppression of AnAOB in the long-term operation, which was mainly due to the disintegration in granules demonstrated by sludge morphology. This selective inhibition is associated with variational sludge morphology and functional bacteria distribution has an important role in the feasibility and stability of PN/A treating acrylic fiber wastewater. As above, this study demonstrated the feasibility of PN/A for acrylic fiber wastewater treatment, but wastewater dilution or pre-treatment would still be required for efficient nitrogen removal.

Keywords: Acrylic fiber wastewater, anammox, PN/A, Industry wastewater, MBR