Long-term evaluation of the effect of peracetic acid on a mixed aerobic culture: Organic matter degradation, nitrification, and microbial community structure

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Peracetic acid (PAA) has been widely used as a disinfectant in many industries; its use in poultry processing is steadily increasing. However, information related to the potential inhibitory effect of PAA solutions (PAA and H2O2) on biological wastewater treatment processes used by the poultry processing industry is extremely limited. The work reported here assessed the long-term effect of PAA solution on aerobic degradation and nitrification in three bioreactors fed with poultry processing wastewater by quantifying the extent of COD removal and nitrification rates. Changes in culture viability, intracellular reactive oxygen species (ROS), and microbial community structure were also evaluated. COD removal and nitrification were not affected by H2O2 and PAA solutions added to the wastewater before feeding (indirect addition). However, both processes were significantly affected by high levels of H2O2 (i.e., 27 mg/L) and PAA solution (i.e., 60/8.4 mg/L PAA/H2O2) directly added to the reactors. Directly added PAA/H2O2 at 40/5.6 mg/L was the lowest dose resulting in nitrification inhibition. Fast recovery of COD removal and nitrification was observed when direct addition of H2O2 and PAA solution ended. Cell viability measurements revealed that the negative impact on nitrification was predominantly attributed to enzyme inhibition rather than to loss of cell viability. The impact on nitrification was not related to intracellular ROS levels. Microbiome analysis showed major shifts in community composition during the long-term addition of H2O2 and even more with PAA addition. No significant time-trend change in the relative abundance of ammonia-oxidizing bacteria or nitrite-oxidizing bacteria was observed, further supporting the conclusion that the negative impact on nitrification was attributed mainly to enzyme inhibition.