Effect of oxic/anoxic conditions on the removal of organic micropollutants in the activated sludge process

Among the emerging issues in the field of wastewater treatments, reducing energy consumption and removal of new organic pollutants have become of primary concern. With respect to the first goal, alternating oxic/anoxic conditions in the bioreactor has demonstrated to be a feasible way to ensure the required efficiency of carbon and nitrogen removal along with energy saving. The aim of the present study was to investigate if these alternating oxic/anoxic conditions are also capable of boosting organic micropollutants degradation, by stimulating the appropriate enzymes. Three different aeration frequencies were tested in a laboratory scale activated sludge reactor and the effects evaluated in terms of removal of carbon, nitrogen and a mixture of OMPs (Sulfamethoxazole, Sulfadiazine, Lincomycin, Carbamazepine, Pyrazole, Naproxen, Atrazine and Sucralose). It was also evaluated if these aeration strategies could change the microbial community composition with respect to the control test conducted under continuous air supply. Among the tested strategies, the longest and shortest durations of anoxic conditions promoted the best removal for the majority of OMPs. This enhancement was statistically well correlated to the activity increase of Lignin Peroxidase and Cellulase enzymes whereas the microbial speciation did not change statistically. The same durations were also capable of maintaining high carbon and nitrogen removal rates within the same biological reactor.