Cometabolic biotransformation of benzotriazole in nitrifying batch cultures

• Published in: Chemosphere (Oxford) 2021-05, Vol.270, p.129461, Article 129461
• Main Authors: Trejo-Castillo, Rubén, El Kassis, Elie Girgis, Cuervo-López, Flor, Texier, Anne-Claire
• Format: Article
• Language: English
• Subjects: Ammonium monooxygenase; Batch Cell Culture Techniques; Benzotriazole; Bioreactors; Biotransformation; Cometabolism; Emerging organic contaminants; Nitrification; Nitrifying conditions; Sewage; Triazoles
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2020.129461

Benzotriazole (BT) is a corrosion inhibitor widely distributed in aquatic environments. Little is known about the cometabolic capacity of stabilized nitrifying sludge to biotransform BT. The contribution of the nitrification process in the simultaneous oxidation of ammonium and biotransformation of BT (5 mg/L) was evaluated in 49 d batch cultures inoculated with a sludge produced in steady-state nitrification. The nitrifying sludge could consume BT in the obligate presence of ammonium. A higher cometabolic biotransformation capacity was obtained by increasing the initial ammonium concentration (100–300 mg N/L), reaching 2.3- and 5.8-fold increases for efficiency and specific rate of BT removal. At 300 mg NH4+-N/L, the sludge biotransform 40.8% of BT and 77.6% of ammonium which was completely oxidized into nitrate. In assays with allylthiourea added as specific inhibitor of ammonium monooxygenase (AMO), it was shown that the totality of BT cometabolic biotransformation was associated with the AMO activity. The addition of acetate did not favor heterotrophic biotransformation of BT. BT provoked inhibitory effects on nitrification. This is the first study showing the role of ammonium oxidizing bacteria in the cometabolic biotransformation of BT and their potential use for cometabolism application in treatment of wastewater contaminated with ammonium and BT. [Display omitted] •A physiologically stable nitrifying sludge was able to biotransform 40.8% of BT.•Simultaneous nitrification and BT biotransformation occurred in batch cultures.•Benzotriazole was cometabolically consumed in the obligate presence of ammonium.•Increasing ammonium concentrations provoked an increase in benzotriazole removal.•The AMO enzyme was involved in the benzotriazole cometabolic biotransformation.