BACKGROUND The aim of this work was to study the biological treatment of a synthetic wastewater containing emerging contaminants. The 95‐day experiment was conducted in an 81 L continuous flow conventional activated sludge apparatus consisting of anoxic and aerobic reactors with internal recycling, and a clarifier with activated sludge recycling. Real activated sludge from the municipal wastewater treatment plant in the Nur‐Sultan city was used. The degradation efficiencies of caffeine, metronidazole, and ibuprofen in the synthetic wastewater were studied either separately or in combination. RESULTS When treated separately at the concentration of 30 mg/L, the degradation of caffeine and ibuprofen was up to 100%, while the degradation of metronidazole was in the range of 12–27%. Caffeine and ibuprofen inhibited the nitrification process, while the presence of metronidazole in the system suppressed the activity of denitrifying microorganisms. The biological treatment of the synthetic wastewater containing all three compounds (at the concentration of 10 mg/L each) resulted in degradation of caffeine and ibuprofen up to 100%, and 56% in the case of metronidazole. As both nitrification and denitrification processes were affected, the total nitrogen removal was significantly reduced from 53% to 22%. CONCLUSION Complete degradation of caffeine and ibuprofen, and partial degradation of metronidazole were observed in a synthetic wastewater using the activated sludge process. As the presence of emerging pollutants in a wastewater affects the general efficiency of the wastewater treatment plants, other physical or chemical pre‐treatment should be utilized to minimize the harmful effect of contaminants on the biological processes. © 2021 Society of Chemical Industry

In the present work, the effect of 2-chlorophenol and 2,4,6-trichlorophenol on the performance of a sequencing batch reactor operated with suspended municipal recycle activated sludge (RAS) in terms of total carbon and total nitrogen removal is presented. The total carbon removal achieved ranged in 80-100% and total nitrogen removal in 10-84%. The results showed that chlorophenols did not inhibit either the activated sludge growth or the total carbon removal significantly. However, inhibition is observed in total nitrogen removal. 2-chlorophenol inhibited the ammonium oxidation (nitrification) while such an effect was not observed in the case of 2,4,6trichlorophenol indicating that the later inhibits the ammonification step. Furthermore, under the experimental conditions examined, complete removal of both chlorophenols was observed after few days of operation.

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