Effect of wastewater COD/N ratio on aerobic nitrifying sludge granulation and microbial population shift.
The effect of COD/N ratio on the granulation process and microbial population succession was investigated. Four identical sequencing batch reactors, R1, R2, R3 and R4, were operated with various initial COD/N ratios ranging from 0/200 to 800/200 (m/m). Ethanol was fed as the source of COD. Aerobic granules were successfully cultivated in R2 and R3, operating with the COD/N ratio of 200/200 and 400/200, respectively. Scanning electron microscope observations indicated that short rod-shaped and spherical bacteria were dominant in R2, while granules produced in R3 were surrounded with a large amount of filamentous bacteria. The average specific nitritation rate in R2 and R3 were 0.019 and 0.008 mg N/(mg MLVSS x hr), respectively. Fluorescence in situ hybridization results demonstrated that nitrifying bacteria population was enriched remarkably in R2. It indicated that nitrification ability and nitrifying bacteria population were enriched remarkably at low COD/N ratio. However, no granules were formed in R1 and R4 which might attribute to either limited or excessive extracellular polymeric substances production. This study contributed to a better understanding of the role of COD/N ratio in nitrifying sludge granulation.
Key Laboratory of Beijing for Water Quality Science and Water Environment Recovery Engineering, Beijing University of Technology, Beijing 100124, China. wulei2008@emails.bjut.edu.cn
Lei
L
Wu
Chengyao
C
Peng
Yongzhen
Y
Peng
Lingyun
L
Li
Shuying
S
Wang
Yong
Y
Ma
D000332:Aerobiosis; D057919:Biological Oxygen Demand Analysis; D059013:Microbial Consortia; D058465:Nitrification; D009584:Nitrogen / Q000032:analysis; D011108:Polymers / Q000032:analysis; D012722:Sewage / Q000032:analysis / Q000737:chemistry* / Q000382:microbiology
D011108:Polymers; D012722:Sewage; D009584:Nitrogen