Effects of oxygen concentration on N-removal in an aerobic granular sludge reactor.
In order to optimise nitrogen removal in an aerobic granular sludge system, short- and long-term effects of decreased oxygen concentrations on the reactor performance were studied. Operation at decreased oxygen concentration is required to obtain efficient N-removal and low aeration energy requirement. A short-term oxygen reduction (from 100% to 50%, 40%, 20% or 10% of the saturation concentration) did not influence the acetate uptake rate. A lower aerobic acetate uptake at lower oxygen concentrations was obviously compensated by anoxic acetate uptake. Nitrogen removal was favoured by decreased oxygen concentrations, reaching a value of 34% for the lowest oxygen concentration tested. Long-term effects were evaluated at two oxygen saturation levels (100% and 40%). Nitrogen removal increased from 8% to 45% when the oxygen saturation was reduced to 40%. However, the granules started to disintegrate and biomass washout occurred. It was impossible to obtain stable granular sludge at this decreased oxygen concentration under applied conditions. A solution to obtain stable aerobic granular sludge at low oxygen concentrations is needed in order to make aerobic granular sludge reactors feasible in practice.
Department of Chemical Engineering, School of Engineering, Avda. Lope Gómez de Marzoa s/n. E-15782 Santiago de Compostela, Galicia, Spain. eqanusmc@usc.es
A
A
Mosquera-Corral
M K
MK
de Kreuk
J J
JJ
Heijnen
M C M
MC
van Loosdrecht
D000085:Acetates / Q000378:metabolism; D001420:Bacteria, Aerobic / Q000378:metabolism*; D018441:Biofilms; D019149:Bioreactors; D009584:Nitrogen / Q000302:isolation & purification*; D010101:Oxygen Consumption; D012722:Sewage / Q000737:chemistry / Q000382:microbiology*; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods
D000085:Acetates; D012722:Sewage; D009584:Nitrogen