Rapid cultivation of aerobic granular sludge by bone glue augmentation and contaminant removal characteristics

To achieve a quick start-up and stable operation, aerobic granular sludge (AGS) was cultivated in a sequencing batch airlift reactor (SBAR) with the addition of bone glue augmentation. Adding an amount of bone glue (40 mg L^–1) can accelerate granulation, which advanced by 10 d on average. Aerobic granules of size 0.5–3.0 mm were dominant in the SBAR and the settling velocity acquired a better correlation with the size of the AGS. In addition, the content of total polysaccharides was 19.54 mg gMLSS^–1 (grams of mixed liquor suspended solids) (an increase of 34.0%), the content of total protein was 60.59 mg gMLSS^–1 (an increase of a factor of 33) and the total proteins/total polysaccharides ratio was 3.3. The relatively high protein content was an essential feature for cultivation of AGS, which may indicate that extracellular polymeric substance was the mechanism for granulation due to the adhesion of microorganisms by bone glue. AGS possessed better chemical oxygen demand, NH₄⁺-N and PO₄^3–-P removal efficiency (of 86.7, 90.6 and 93.8%, respectively) and no nitrite accumulation was observed in the whole process.