The effect of organic loading rate on the aerobic granulation: the development of shear force theory.
The effect of organic loading rate (OLR) on aerobic granulation was studied by adopting three column-shaped, sequential aerobic sludge blanket reactors (SASBR). The reactors had been fed with laboratory prepared, synthetic dextrose-nutrient broth substrate. Experimental results showed clearly that the formation, characteristics and stability of aerobic granules had a close relationship with the strength of OLR applied. Aerobic granules appeared firstly under the OLR of 4 kg COD x (m3 x day)(-1). The system stabilization was demonstrated by its little-changed amount and morphology of granules. The characteristics of the stabilized granules were: 5.4 mm in mean diameter, 1.29 in roundness, 118 mg O2 x (mg VSS x hr)(-1) in SPOUR. The respective biomass SVI was 50 mL x (g MLVSS)(-1) and the averaged COD removal rate was 95%. Under the OLR of 8 kg COD x (m3 x day)(-1), granules appeared two days later than those for 4 kg COD x (m3 x day)(-1) and they always coexisted with flocs. The formed granule bed was not as compact as that under 4 kg COD x (m3 x day)(-1). There were no granules formed under the OLR of 1 kg COD x (m3 x day)(-1). Instead, flocs with rather loose structure dominated reactor mixed-liquor. The respective SVI's were 65 and 138 mL x (g MLVSS)(-1) under OLR of 8 and 1 kg COD x (m3 x day)(-1). It was proposed that the growth and maintenance of aerobic granules follow the shear force balance theory. Under the OLR of 4 kg COD x (m3 x day)(-1), a balance was reached between the aeration shear force and organic loading rate. Under this favored condition aerobic granules formed quickly and, became stabilized with the experimental parameters remained unchanged.
Tay
J H
JH
EERC, CEE, NTU, Blk N1, 50 Nanyang Avenue, Singapore 639798. p6883386h@ntu.edu.sg
Pan
S
S
Tay
S T L
ST
Ivanov
V
V
Liu
Y
Y
D001420:Bacteria, Aerobic / Q000502:physiology; D018533:Biomass; D019149:Bioreactors; D010100:Oxygen; D010316:Particle Size; D012722:Sewage / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014872:Water Movements; D018508:Water Purification / Q000379:methods*
D012722:Sewage; D010100:Oxygen