Applying disease or pathogen control treatments in recirculating aquaculture systems (RAS) can be challenging due to the potential impacts of the administered chemical agent(s) on biofilter performance. Fish farmers utilizing RAS would benefit greatly from possessing more treatment options that are both efficacious towards the intended microbial target(s) and relatively safe in terms of maintaining biofilter function for sufficient nitrification of accumulating ammonia. One particular chemical, peracetic acid (PAA), has shown promise outside the United States for use in controlling disease and pathogen counts in commercial RAS; however, PAA’s use in the U.S. aquaculture is currently restricted to materials surface disinfection when food fish are not present. Before approval of PAA as a bona fide aquacultural therapeutant is considered, baseline research is required to assess, among other things, the impact on nitrification as RAS biofilters are exposed to PAA.
To address this knowledge gap, we exposed replicated experimental-scale freshwater fluidized sand biofilters to 4-hour exposures of semi-continuous low-dose PAA at three separate concentrations, and monitored PAA concentration over time to assess peak concentrations achieved as well as chemical decay following cessation of treatments. Following PAA exposure, we monitored all biofilters for a period of two weeks and assessed total ammonia nitrogen (TAN) removal efficiencies, influent and effluent nitrite- and nitrate-nitrogen concentrations, and bacterial biomass. At the time of abstract submission, the study is ongoing, with anticipated final data collection in November 2021. Final PAA dose-response impacts on RAS biofilter performance, as well as recommendations for PAA use in RAS based on study results, will be presented at Aquaculture America 2022.