Operational performance and sludge morphology shifts during long-term operation of a full-scale industrial aerobic granular sludge membrane bioreactor (AGMBR)

This is the authors' abstract. We don't add key points for this paper.

This study analyzed the ultrafiltration (UF) properties of two full-scale industrial membrane bioreactors (MBRs), treating similar wastewater originating from food tank truck cleaning (TTC), over the course of one year. The first MBR, An-MBR, used an anaerobic feeding strategy to microbially select slow-growing glycogen-accumulating organisms (GAOs), and aerobic granular sludge (AGS) whereas the second MBR, Ae-MBR, was a conventional fully aerobic MBR. The Ae-MBR's UF permeability was 58% lower than in the An-MBR. The integration of AGS with UF was detrimental to the granular morphology, but, despite losing granular morphology, the An-MBR exhibited a high abundance of GAOs (up to 9.55%) and an anaerobic DOC uptake of 71.35%, compared to 7.71% for the Ae-MBR. In addition, the An-MBR sludge showed faster dewaterability, lower viscosity and a higher sustainable flux compared to the Ae-MBR sludge. These improved UF properties correspond to clear operational benefits: the An-MBR consumed 2.53 kW h/m 3 compared to 4.21 kW h/m 3 for the Ae-MBR, and required less frequent membrane cleaning, resulting in lower cleaning costs. The better UF performance can most probably be explained by the higher ratio of proteins to polysaccharides (PN/PS of 2.52 vs. 0.3) in the An-MBR sludge EPS leading to a higher sludge relative hydrophobicity (69% vs. 42%). Anaerobic feeding might be the reason for the higher PN/PS ratio and a higher relative hydrophobicity. However, a nutrient shortage may also have affected the EPS composition, and this needs further investigation.