Population dynamics of nitrifying sludge supplemented with 2-chlorophenol in SBR reactors

BACKGROUND The metabolic improvement and reduction of the inhibitory effect of 2-chlorophenol (2-CP) on the nitrification process occurring in nitrifying SBR systems can be associated with changes in the microbial community. The physiologic, kinetic, and microbial population behaviors of two nitrifying sludges were evaluated in two parallel sequencing batch reactors (SBR1 and SBR2) amended with 2-CP. Seven cycles were performed with 20 to 60 mg 2-CP-C/L. RESULTS Ammonium-oxidizing and nitrite-oxidizing processes were physiologically disturbed in SBR1 and SBR2 due to increased 2-CP concentrations, attaining ammonium consumption efficiencies (ENH4+-N) and nitrate yields (YNO3--N) as low as 38% and 0.32 mg NO3--N/mg NH4+-N consumed, respectively. Nevertheless, in cycle 7, both sludges recovered their physiological capacities, as ENH4+-N of 100% and YNO3--N > 0.94 mg NO3--N/mg NH4+-N consumed were achieved in both nitrifying processes. Increase in 2-CP concentration also affected the kinetics of nitrification processes, wherein a higher inhibition on the specific rate of ammonium-oxidizing process was observed. Despite the increase in 2-CP concentration, no predominance of species was noted, as the bacterial community evenness index remained above 0.97, whereas the richness index increased along with SBR operation. CONCLUSION The stable, complete, and efficient nitrifying process achieved in both SBRs could be related to the higher bacterial community richness and to the regular maintenance of ammonium and nitrite oxidizing bacteria tolerant to 2-CP along experimentation. Total 2-CP consumption might be associated with ammonium-oxidizing and/or heterotrophic bacteria related to Nitrosospira, Luteimonas, and Cohnella. (c) 2021 Society of Chemical Industry (SCI).

Automated summary

The metabolic improvement and reduction of the inhibitory effect of 2-chlorophenol (2-CP) on the nitrification process occurring in nitrifying SBR systems can be associated with changes in the microbial community. The stable, complete, and efficient nitrifying process achieved in both SBRs could be related to the higher bacterial community richness and to the regular maintenance of ammonium and nitrite oxidizing bacteria tolerant to 2-CP along experimentation. Total 2-CP consumption might be associated with ammonium-oxidizing and/or heterotrophic bacteria related to Nitrosospira, Luteimonas, and Cohnella.