Evaluation of the effect of peracetic acid solution on the performance of a continuous-flow biological nitrogen removal (BNR) system

Peracetic acid (PAA) has been extensively used in poultry processing plants as an effective disinfectant alternative to chlorine-based products. However, PAA-bearing poultry processing wastewater, as part of the regular disinfection process and/or in case of accidental spills, can lead to severe upsets of biological wastewater treatment processes. The objective of this study was to assess the short- and long-term effect of PAA solution (PAA and hydrogen peroxide, H2O2) on the performance of a continuous-flow biological nitrogen removal (BNR) system, fed with poultry processing wastewater. The system consisted of three reactors in series: anaerobic (R1), anoxic (R2), and aerobic (R3). Continuous, direct addition of PAA solution up to 200/28.6 mg/L PAA/H2O2 (feed-based concentration) to the anaerobic reactor (R1) did not affect the performance of the BNR system, which achieved over 90 and 82% COD and N removal, respectively. However, both COD and N removal were negatively affected by continuous feeding with residual PAA-bearing wastewater at 80 and 200 mg/L. PAA was self-decomposed or by reaction with other wastewater components, such as proteins and transition metals, rather than being biodegraded. Fast recovery of COD and N removal was achieved within three retention times feeding with PAA/H2O2-free wastewater. The BNR system was more susceptible to residual PAA without the R1, i.e., two-reactor system. Complete recovery from the impact of residual PAA was achieved, suggesting the effect of PAA on system performance was fast reversed and not lasting. The impact on the BNR system was a combination of enzyme inhibition and cell lysis leading to biomass loss. The PAA impact in R1 (anaerobic) on Synergistales and Bacteroidales was reversed, but not on Lactobacillales and Pseudomonadales. Campylobacterales and Sphingomonadales were enriched when PAA was fed to the BNR system. Betaproteobacteriales, Sphingobacteriales and Rhodobacterales in R2 (anoxic) and R3 (aerobic) reactors were negatively affected by PAA, but the impact was fast reversed when PAA addition was ceased.