Characterization of aerobic granular sludge of different sizes for nitrogen and phosphorus removal

ABSTRACT

Granular size plays a key role in the performance of the aerobic granular sludge (AGS). As the diameter of the granule increases, stratification may begin to appear due to the increase in mass transfer resistance. Aerobic granules harvested from a lab-scale anaerobic–aerobic sequencing batch reactor (AO-SBR) were classified into three categories according to their size: (a) 0.15–0.28 mm, (b) 0.28–0.45 mm and (c) larger than 0.45 mm. In this study, the categories were called small-size, medium-size and large-size granules, respectively. A fraction of the different forms of phosphate and denitrification efficiency was investigated in each category. Results show that small-size granules present much more easily mobile phosphorus than other granules. Moreover, the denitrification performance has been tested by using dumping and trickling patterns for COD and ${\text{NO}}_3^{-}-\text{N}$ feeding. The results demonstrated that the large-size granules exhibit poor denitrification rates, as opposed to the medium-size granules. Therefore, medium-size granules, with a size of 0.28–0.45 mm, are regarded as the most suitable granular size for AGS in this experiment from the perspective of denitrification and phosphorus removal.

GRAPHICAL ABSTRACT

KEYWORDS:

• Aerobic granular sludge (AGS)
• enhanced biological phosphorus removal (EBPR)
• wastewater treatment
• phosphate fraction
• granular size

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Yuan-Mo Zhu http://orcid.org/0000-0002-5499-5977

Additional information

Funding

This work was partially supported by the National Natural Science Foundation of China [grant number 51078303], the Shaanxi Provincial Department of Housing and Urban-Rural Development [grant number 2015-K63], the Xi'an Science and Technology Bureau [grant number 2016063SF/SF09] and the Shaanxi Provincial Department of Water Resources [grant number 2017slkj-10].