Three column sequencing batch reactors (SBR) (R1

R2 and R3) were operated under various aeration intensity of 0.5

1.0 and 1.5 L·min-1

respectively. The influence of aeration intensity on characteristics

treatment performance and biomass of the phosphorus removal granules (PRGs) were investigated. PRGs were formed in all reactors in 30 days and operated steadily for another 30 days. The results showed that the aeration intensity had an important impact on the settling ability

particle size

morphology

moisture content

treatment performance and biomass. With the increase of aeration intensity

the diameter and settling velocity of matured granules were increased

which were 900 μm and 24-144 m·h-1

1000 μm and 29-162 m·h-1

and 1150 μm and 33-178 m·h-1 in R1

R2 and R3

respectively

while the moisture contents were decreased and were 95.6%

94.2% and 93.4%

respectively. Therefore

compared with the low aeration intensity

the PRGs under the higher aeration intensity had better physical characteristics

settling ability and treatment performance due to the more biomass and denser structure. PRGs under higher aeration intensity were spherical or elliptic and had regular contours

but the structure and shape of PRGs under lower aeration intensity was loosened and irregular. Meanwhile

the MLVSS/MLSS

biomass layer thickness of PRGs and P release/COD uptake ratios in all reactors at the 51th day were calculated. MLVSS/MLSS and biomass layer thickness of granules in R1

R2 and R3 were 78% and 0.34 mm

82% and 0.35 mm

and 86% and 0.38 mm

respectively. It demonstrated that granules in the reactor with higher aeration intensity had a relatively thicker biomass layer and more biomass. The P release/COD uptake ratios in R1

R2 and R3 were 0.35

0.35 and 0.36

respectively

indicating that the content of phosphorus accumulating organisms (PAOs) was high in all reactors of this research.