Methanol Regulate the Performance and Microbial Assembly in the Partial Denitrification-Anammox System

Abstract

Anaerobic ammonium oxidizing (anammox) and nitrifying bacteria, two commonly widespread microorganisms, are critical for the microbial nitrification in wastewater treatment facilities. Organic compounds have been well-known as perturbators for the growth and assembly of anammox and nitrifying bacteria, while how these organic carbon affect anammox is an open question. Here, this study investigates the impacts of methanol on the nitrogen removal efficiency, bio-aggregation capacity, and community composition of the anammox consortia in wastewater. The inhibition of methanol on anammox was concentration-dependent and irreversible; 0.35 mM methanol slightly increased effluent ammonium and nitrite concentrations, and greater than 0.35 mM methanol almost significantly inhibited anammox after 54 hours of denitrification. Moreover, methanol also increased consortia hydrophobicity and decreased bio-aggregation capacity, characterized by reduced soluble protein and increased soluble polysaccharide concentrations. The microbial community shifts after methanol exposure, while 16S rRNA analysis showed positive correlations between methanol concentration and heterotrophic denitrifying bacteria (e.g., Methyloversatilis and Caldilinea), ammonia-oxidizing bacteria (e.g., Nitrosomonas), and nitrite oxidizing bacteria (e.g., Nitrospira). Thus, the heterotrophic bacteria could enhance the anammox process through strengthening interactions with anaerobic anammox bacteria, methane and nitrogen metabolic pathways. These findings provide valuable insights for maintaining efficient denitrifying/anammox processes in the presence of varying organic compound concentrations in aqueous environments.

Keywords: Wastewater, Anammox, methanol, Nitrogen Removal, Community assembly