Application of Ozone in Full-Scale to Reduce Filamentous Bulking Sludge at Öresundsverket WWTP

The return sludge of one of the four treatment lines at Öresundsverket WWTP in Sweden was subjected to ozonation in full-scale to reduce filamentous bulking sludge. The biological nitrogen and phosphorus removal capacity along with effluent parameters were studied throughout the trial. Samples were also taken to track possible changes in microbial population due to ozone. 2.8-5.0 g O₃ kg^-1 treated SS^-1 reduced the DSVI of the ozone-treated line from 170 to 100 mL g^-1 and the reference line remained at 150 mL g^-1. No adverse effect on the biological nitrification- or the phosphorus removal rates could be detected. The microbial population of the two lines did not exhibit any substantial changes which can be correlated to ozone addition.