Performance change during long-term ozonation aimed at augmenting denitrification and decreasing waste activated sludge.
Partial ozonation of return activated sludge for waste sludge minimization and soluble COD production was examined. Two nitrifying sequencing batch reactors, one control and one ozonated, were operated under alternating anoxic/aerobic conditions. During the first steady-state period of 95-136 d of ozonation, the amount of wasted solids decreased with the ozone dose up to 25%, generating soluble COD by cell lysis. However, during a subsequent period of 190-232 d of continuous ozonation, the effect of solids destruction and COD production decreased by 50%. The investigations of extracellular polymers content and floc shape analyses showed that, after prolonged daily ozone treatment, sludge floc structure becomes stronger, denser, and more ozone-resistant. The findings suggest that, for prolonged operation of partial sludge ozonation, an increase in ozone doses may be required to continuously maintain the expected solids destruction level. This in turn will increase the operational costs of the treatment.
Department of Civil Engineering, University of Manitoba, 15 Gillson Street, Winnipeg, MB, Canada R3T 5V6.
Magdalena A
MA
Dytczak
Jan A
JA
Oleszkiewicz
D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors / Q000382:microbiology; D058440:Denitrification / Q000187:drug effects*; D005427:Flocculation; D010126:Ozone / Q000737:chemistry* / Q000378:metabolism; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000378:metabolism
D012722:Sewage; D014874:Water Pollutants, Chemical; D010126:Ozone