Surface convexity of anammox granular sludge: Digital characterization, state indication and formation mechanism

• Published in: Environment international 2019-10, Vol.131, p.105017, Article 105017
• Main Authors: Kang, Da, Guo, Leiyan, Hu, Qianyi, Xu, Dongdong, Yu, Tao, Li, Yiyu, Zeng, Zhuo, Li, Wenji, Shen, Xiaojing, Zheng, Ping
• Format: Article
• Language: English
• Subjects: Anammox granular sludge; Bioreactors; Formation mechanism; Nitrogen - chemistry; Nitrogen - metabolism; Oxidation-Reduction; Performance indicator; Relative lightness; Sewage - chemistry; Surface convexity
• ISSN: 0160-4120; 1873-6750
• DOI: 10.1016/j.envint.2019.105017

Anammox granular sludge system is a promising biotechnology for nitrogen removal from wastewaters. The anammox granules possess the distinctive morphological features which can be developed as visible indicators for anammox process monitoring. In this study, the surface convexity of anammox granular sludge (AnGS) was systematically investigated for the first time. The AnGS was withdrawn from four long-term operated anammox bioreactors at different nitrogen loading rates. Firstly, the spherical convexity and gap concavity with a diameter of 50–100 μm were observed to be distributed on the granules surface under the microscopic observation. Then, the surface convexity was determined by image processing technology and the statistical analysis showed that the convexity had a significant difference (p = 0.003) among bioreactors and the average surface convexity decreased from 0.937 ± 0.030 to 0.899 ± 0.034, and then rose to 0.914 ± 0.035 which had a significant correlation with the volumetric gas production rate of bioreactor (r = −0.873, p