Granule formation mechanism, key influencing factors, and resource recycling in aerobic granular sludge (AGS) wastewater treatment: A review

Microbial Ecology of Granular Biofilm Technologies for Wastewater Treatment: A Review

“…During the formation of granules from activated sludge inoculum, the microbial community changes and is selected according to the bioreactor and environmental conditions. Hydrodynamic forces, EPS secretion, filamentous microorganisms, and protozoa play an important role in the granulation process that starts with the contact between microorganisms, after which a three-dimensional structure is created, and finally, the granule is stratified [ 22 , 23 ].…”

“…Fungi could be more implied in granule formation when pH is low, whereas, at a higher pH, filamentous bacteria are more involved than fungi [ 32 ]. Some of these filamentous bacteria are members of the Roseiflexus and Chloroflexi genera [ 23 , 39 ]. Species of Coriolus , Phanerochaete , or Aspergillus are fungi that enhance granulation [ 40 , 41 ].…”

“…In fungi, the phylum Ascomycota has been recognized for its capacity for nitrogen removal [ 26 ]. Some studies have reported that algal–bacterial granular sludge can increase nutrient removal and be energy saving [ 23 , 61 ]. Nitzschia , Chlorella , Neodesmus , Scenedesmus , Leptolyngbya , Oxyphotobacteria , Prochlorotrix , and Auxenochlorella are algae found in AGS [ 17 , 45 , 61 , 62 ].…”

“…The EBPR process consists of alternating anaerobic and aerobic phases. During anaerobic conditions, PAOs hydrolyze poly-P to obtain energy, whereas, in aerobic conditions, they uptake and accumulate the excess P in the form of poly-P [ 23 ]. In addition, EPS plays an important role in P removal because poly-P is also accumulated in EPS bound to cells [ 17 ].…”

“…In addition, EPS plays an important role in P removal because poly-P is also accumulated in EPS bound to cells [ 17 ]. Another mechanism for P removal is the precipitation with Ca or Mg [ 23 , 34 , 65 ]. PAOs and GAOs are considered slow-growing microorganisms, and they can be found in the outer and inner layers of dense granules with anoxic microenvironments [ 17 , 22 , 34 ].…”