Simultanous Pyridine Biodegradation And Nitrogen Removal In Aerobic Granular System

Simultaneous pyridine biodegradation and nitrogen removal were successfully achieved in a sequencing batch reactor (SBR) based aerobic granules. In a typical SBR cycle, nitritation occurred obviously after the majority of pyridine was removed, while denitrification occurred at the early stage of the cycle when oxygen consumption was aggravated.The effects of several key operation parameters, i.e., air flow rate, cycle duration, influent NH4Cl concentration, influent pH and pyridine concentration on nitritation, pyridine degradation, total nitrogen (TN) removal and Extracellular Polymeric Substances (EPS) production, were systematically investigated. The results indicated that high air flow rate had a positive effect on pyridine degradation and nitritation but a negative impact for overhigh air flow rate; both nitritation and TN removal could be severely inhibited at too short cycle duration; With the increase of influent NH4Cl concentration, both nitritation and TN removal could be gradually inhibited; Slightly alkaline condition, i.e., pH 7.0-8.0, was beneficial for both pyridine degradation and nitritation, while high pH and low pH often resulted in the delay of pyridine degradation and nitritation; high pyridine dosage often resulted in the delay of both pyridine degradation and nitritation. Besides, EPS contents increased with the increase of air flow rate, but decreased with the increase of NH4+ dosage; the appropriate starvation phase will promote the secretion of EPS, while too long and too short cycle duration often resulted in the decrease of EPS production; high EPS production was observed at pH of 7.5, while high pH and low pH often resulted in the decrease of EPS production; EPS production increased with the increase of pyridine dosage, but decreased with the further increase of pyridine dosage. Finally, this study built an alternating anaerobic-aerobic sequencing batch reactor, explore the effect on pyridine degradation and TN removal.High-throughput sequencing technology was applied to study the microbial community structure of the SBR for examining the important role of various microbes played in this aerobic granular system. The results demonstrate that Bdellovibrio and Paracoccus were the dominant species of the aerobic granular system. In addition, this paper made a comparative difference analysis of the microbial community structure with the aerobic granule in previous study which only have the ability to degrade pyridine. The coexistence of pyridine degrader, nitrification related species, denitrification related species, polymeric substances producer and self-aggregation related species in this aerobic granular system was confirmed, combining with the aforementioned analysis of pyridine and nitrogen removal, EPS variation, the possible mechanisms responsible for the simultaneous pyridine and nitrogen removal was proposed.