Effect of calcium addition on the formation and maintenance of aerobic granular sludge (AGS) in simultaneous fill/draw mode sequencing batch reactors (SBRs)

• Published in: Journal of environmental management 2020-02, Vol.255, p.109850-109850, Article 109850
• Main Authors: Barros, Antônio Ricardo Mendes, Rollemberg, Silvio Luiz de Sousa, de Carvalho, Clara de Amorim, Moura, Ian Holanda Herbster, Firmino, Paulo Igor Milen, dos Santos, André Bezerra
• Format: Article
• Language: English
• Subjects: Aerobic granular sludge; Aerobiosis; Bioreactors; Calcium; Calcium addition; Sewage; Simultaneous fill/draw mode SBR; Waste Disposal, Fluid
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2019.109850

This work investigated the effect of Ca2+ (100 mg L−1) addition on the formation and maintenance of aerobic granular sludge in a simultaneous fill/draw mode sequencing batch reactor (SBR), operated with a low liquid upflow velocity (0.92 m h−1), in order to verify if Ca2+ presence compensates the low selection pressure imposed. Additionally, carbon and nutrients removals, granules characteristics and microbial community were evaluated. For this, two SBRs (R1, control, and R2, Ca2+-supplemented) were operated (6-h cycle). In general, Ca2+ supplementation affected positively the sludge settleability, although a larger fraction of inert solids was found in the granules. The total extracellular polymeric substances were the same for both reactors, and no remarkable differences were observed between their polysaccharides and proteins contents. Overall, Ca2+ addition in a simultaneous fill/draw mode SBR neither accelerated the granule formation nor improved the operational performance. The microbial community structure, especially in terms of bioactivity, was not affected as well. Therefore, the effect of divalent cations might be more pronounced in conventional SBRs, in which the selection pressure is higher. •AGS was cultivated in a simultaneous fill/draw mode SBR supplemented with Ca2+.•Ca2+ affected positively sludge settleability, but it did not change EPS content.•Ca2+ increased the species richness, but it did not affect the microbial activity.•The effect of Ca2+ addition seems to be more pronounced in conventional SBRs.•EDX analysis showed that Ca2+ did not increase P content in the AGS.