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

Abstract

The objective of this study was to assess the long-term effect of peracetic acid (PAA) solution on anoxic organic matter degradation and denitrification. Three bioreactors (R1, R2, and R3) were operated for 166 d, fed with poultry processing wastewater and gradually increased H2O2 (R2) or PAA solution (i.e., PAA + H2O2)(R3). Organic matter degradation, quantified as the extent of COD removal, and denitrification were assessed. COD removal and denitrification 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, but fast recovery was observed when direct addition of H2O2 and PAA solution ended. The negative impact on denitrification was the combined result of enzyme inhibition and loss of cell viability, both related to increased intracellular ROS levels. Partial acclimation to PAA solution took place during the long-term operation, resulting in higher denitrification activity, higher cell viability and lower intracellular ROS than in a short-term batch assay with one-time PAA addition. Microbiome analysis showed major shift in community composition during the long-term operation with PAA solution addition, but no significant shift after the long-term operation with H2O2 addition. Among the main denitrifying genera, Thauera and unclassified Chitinophagaceae were negatively impacted while Chryseobacterium and unclassified Enterobacteriaceae were enriched during the long-term operation with PAA addition.