[Description of the stability of granules using nongrowth-related parameters]

Qualitative rather than quantitative method was available in the study of aerobic granular sludge. This work therefore investigated two systems, one was the conventional heterotrophic system without anaerobic mix period, the other was the phosphorous removal system with anaerobic period, and it was found that the latter was more stable from the point view of diameter, density and morphology. It was further found that the stability of granule was associated with the metabolic characteristics, i. e., the slow growth system showed more stability may be due to higher fraction of maintenance metabolic energy. In order to evidence that, different size of granule in the slow growth system was obtained for the metabolic character analysis. It was found that the maintenance coefficient m and the ratio of maintenance COD consumption ratio S(min)/COD(influent) was well correlated with the stability of granules. Consequently, it was proposed that these two parameters could be used for the quantitative description of the stability of granules. This study established a new method for the quantitative description of the stability of aerobic granules from the metabolic perspective, which improved the conventional qualitative methods in terms of morphology, diameter and density of granules.