Cell surface characterization and trace metal adsorptive properties of anaerobic ammonium-oxidizing (anammox) consortia

Interactions between metals and anaerobic ammonium oxidizing consortia substantially affect the quality of wastewater treatment plant effluent. In this study, we conducted acid-base titrations to ascertain the surface reactivity and proton adsorptive capacity of anammox consortia. A combination of titration data modeling and infrared spectroscopy suggested the presence of carboxyl, amine, and hydroxyl groups. Cd adsorption experiments demonstrate that 1 g of dry biomass could bind an equivalent of 7.12 x 10(-6) mol/L of Cd. Density functional theory calculations further reveal that carboxyl and hydroxyl groups are able to form stable Cd complexes. Furthermore, considerable carboxyl and hydroxyl groups promote bacterial aggregation, and thus solid-liquid separation. The results of this study highlight the potential role of anammox consortia in adsorbing metal cations, and thus help to improve the understanding of the universally significant contribution of anammox consortia at the detoxification of metal cations in wastewater treatment systems. (C) 2019 Elsevier Ltd. All rights reserved.