Decay of peracetic acid in seawater and implications for its chemotherapeutic potential in aquaculture

Lf Pedersen,Cc Lazado

doi:10.3354/aei00354

Abstract

Peracetic acid (PAA) is a widely applied disinfectant in aquaculture. Knowledge on PAA decay in seawater (SW) is crucial for its successful implementation in SW aquaculture systems. We investigated the decay dynamics of PAA in SW under controlled conditions to assess the potential effect of temperature, salinity and light. We also applied PAA to 22 tanks with post-smolt Atlantic salmonSalmo salarin full-strength SW (33‰) over a realistic range of therapeutic concentrations (0.15-4.8 mg l-1) to simulate relevant treatment scenarios. The study showed that PAA degrades rapidly in SW. The degradation follows exponential first-order decay with half-lives on the order of minutes to hours. Salinity and temperature significantly affected the decay of PAA, showing a 4-fold faster decay rate in full-strength SW compared to freshwater. The decay of PAA was not significantly related to the nominal concentration of PAA in the concentration range tested. The other 2 active ingredients in PAA products, hydrogen peroxide (H2O2) and acetic acid, were found to degrade at a much slower rate. H2O2half-lives in SW were found to range from 15 to 70 h, and minimal acetate was found to be degraded when added to SW. Finally, we compiled published data on PAA decay in relevant water matrices and discussed the potential environmental impacts, mitigation options and future research.

Highlights

Peracetic acid (PAA) or peroxyacetic acid, a biocidal peroxygen compound, constitutes the main active component in PAA-containing trade products
PAA forms free radicals in reaction with organic matter and transition metals, PAA is considered unspecific in its mode of action which leaves PAA resistance quite unlikely (EU 2012)
The degradation of PAA is rapid (T1⁄2 values on the order of 1−2 h), and T1⁄2 values are lower in saline water compared to freshwater

Summary

Introduction

Peracetic acid (PAA) or peroxyacetic acid, a biocidal peroxygen compound, constitutes the main active component in PAA-containing trade products (cf. excellent reviews by Kitis 2004 and Luukkonen & Pehkonen 2017). Trade solutions contain PAA from 5−40 w/w% (typically between 10 and 15%), H2O2 and acetate (both ranging from 15−30%) (Kitis 2004, Muñío & Poyatos 2010, Liu et al 2015). PAA has powerful biocidal and biostatic effects, as it forms free radicals such as hydroxyl (cf mode of action by Wessels & Ingmer 2013), is effective at low tempera-. PAA forms free radicals in reaction with organic matter and transition metals, PAA is considered unspecific in its mode of action which leaves PAA resistance quite unlikely (EU 2012). The inhibition of catalases has been proposed as a mechanism of the synergistic effect of PAA and H2O2 (Flores et al 2014)

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Discussion

Conclusion