The long-term effect of glutaraldehyde on the bacterial community in anaerobic ammonium oxidation reactor

[Display omitted] •The effect of disinfectant-glutaraldehyde on the PN-ANAMMOX process was assessed.•Glutaraldehyde caused the anammox bacteria eroded from granule to flocus.•Glutaraldehyde alters nitrogen metabolism pathways and causes the increase of nir and nor genes.•NodT related efflux pumps replacing TolC related ones may be potential resistance mechanism.•Anammox bacteria lacked the NodT proteins and was sensitive to Glutaraldehyde. A 160-day incubation was performed with two anammox reactors (GA and CK) to investigate the effect of glutaraldehyde. The results indicated that anammox bacteria were very sensitive when glutaraldehyde in GA reactor increased to 40 mg/L, the nitrogen removal efficiency sharply decreased to 11%, only one-quarter of CK. Glutaraldehyde changed spatial distribution of exopolysaccharides, caused anammox bacteria (Brocadia CK_gra75) to disassociate from granules (24.70% of the reads in CK but only 14.09% in GA granules). Metagenome analysis indicated glutaraldehyde led to the denitrifier community succession from strains without nir (nitrite reductase) and nor (nitric oxide reductases) genes to those with them, and the rapid growth of denitrifiers with NodT (an outer membrane factor)-related efflux pumps replacing those with another TolC -related ones. Meanwhile, Brocadia CK_gra75 lacks the NodT proteins. This study provides important insight into community adaptation and potential resistance mechanism in an active anammox community after exposure to disinfectant.