Synthetic fresh-cut wastewater disinfection and decontamination by ozonation at pilot scale

In this research, the capability of ozonation and peroxone treatment for the simultaneous disinfection and decontamination of wash water from the fresh-cut industry has been investigated at pilot plant scale (10 L). The removal efficiency of six organic microcontaminants (OMCs) (four of them priority substances) and the inactivation of two foodborne pathogens (Escherichia coli O157:H7 and Salmonella enteritidis) in synthetic fresh-cut wastewater (SFCWW) has been assessed. Ozonation and peroxone (O₃ with 20 mgL^-1 of H₂O₂) process has been investigated under several operational conditions: natural SFCWW pH (6.25) and basic pH (11), and two different initial ozone production (0.09 and 0.15 gO₃ L^-1 h^-1). Results showed that the highest efficiency for OMCs removal (85%) and pathogen inactivation (>5-Log) were obtained with ozonation treatment at natural pH. OMCs degradation was obtained after 120 min of treatment with an ozone dose of 27.4 mgO₃ L^-1. First order kinetic constant of each OMC degradation was obtained, and two clear different groups have been identify based on their degradation profiles, which have been correlated with their chemical structure. G₁-OMC [terbutryn > buprofezin > azoxystrobin] > G₂-OMC [imidacloprid > simazine > thiamethoxam]. As for bacterial inactivation, up to 10 min of treatment time and an ozone dose of <8.6 mgO₃ L^-1 were required to reach the detection limit (2 CFU mL^-1), showing E. coli O157:H7 a higher susceptibility to be inactivated (k: 2.79 min^-1) than S. enteritidis (k: 1.47 min^-1). Moreover, from the techno-economical and toxicological assessment of the treated water with the best operational condition, can be highlighted: i) a slight acute toxicity for V. fischeri (47 ± 2.3% of luminescence inhibition), ii) an acute toxicity for Daphnia magna (100% of immobilization) and iii) a total cost of the treatment of 1.16 € m^-3.