| Long-term stability of aerobic granular sludge under low carbon to nitrogen ratio（C/N）is one of the main factors that hinder its practical application.In this study,aerobic granular sludge was cultivated under C/N of 4:1(COD 400 mg·L-1,NH4+-N 100mg·L-1)with activated sludge as inoculum under C/N of 8:1(COD 400 mg·L-1,NH4+-N 50mg·L-1).The physical and chemical characteristics,t reatment performance and long-term stability combined with the changes in the extracellular polymer substances（EPS）and microbial structure of the aerobic granular sludge,were investigated,which provide theoretical and practical basis for the manipulation and stabilization of aerobic granular sludge system under low C/N conditions.It was found:1、Aerobic granular sludge with high settlability were successfully cultivated in the parallel reactor R1 and R2,respectively,MLSS in R1 and R2 were 6.82g·L-1and 5.06g·L-1,SVI30 were in the range of 40-60m L·g-1and the relative hydrophobicity were at about 55%;the removal efficiency for COD and ammonia nitrogen were above 95%and close to 100%,respectively;2、Aromatic extracellular protein was the main component of EPS,with the content of 123.14 mg?g MLVSS-1 in R1 and 229.26mg?g MLVSS-1 in R2,extracellular polysaccharides（PS）was only appeared in the compact layer,which contained soluble microbial by-products and humic acid,these components combined together to maintain stability of the aerobic granular sludge;3、The low C/N in the feed reduced diversity of the microorganisms in the aerobic granular sludge from the formation to mature and stabilization.The microbial populations kept changing,a mong which the richness of nitrifying bacteria increased,Sphingorhabdus with strong adaptability to high ammonia nitrogen gradually appeared,Acidovorax and Hydrogenophag were almost unaffected,bacteria,such as the less competitive Aquimonas,gradually disappeared.The microbial ecosystem continue d evolving and Zoogloea had become the dominant bacteria. |
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