Rapid granulation of aerobic sludge for treatment of brewery wastewater: Aeration strategy and nitrogen removal mechanism

Experimental studies were carried out on rapid granulation of aerobic sludge treating the brewery wastewater and the characteristics of aerobic granular sludge (AGS) formed under the different operating conditions. Two sequencing batch reactors (SBRs) were operated with different aeration modes: R1 under continuous aeration and R2 with intermittent aeration, including an anoxic phase before oxygenation. By shortening the settling period to 5 min to enhance the sludge selection, in combination with the elevated organic loading rate to over 3 kg COD/(m3 center dot d), granulation was rapidly achieved within 2-3 weeks. Compared with R2, under the same loading levels, AGS in R1 was featured with a denser, more uniform shape. R1 exhibited a good nitrogen removal capability even under the complete aerobic condition, attributable to the anoxic zones in the layered-structure of granules, which provides an environment for denitrification. In comparison, R2 demonstrated a superior nitrogen removal performance owing to both the SBR anoxic phase and the more internal anoxic zones for the larger granules, along with a notable energy saving of nearly 40 % due to the shortened aeration period. Microbial analysis revealed the crucial role of specific microbial communities such as OLB8, Chitinivorax, and Anaerolineaceae, which significantly contributed to the efficient degradation of polysaccharides in brewery wastewater.