Hydrogen peroxide application to a commercial recirculating aquaculture system

An important part of the management of recirculating aquacultural systems is to ensure proper rearing conditions in terms of optimal water quality. Besides biofiltration, current methods include use of use of micro-screens, UV irradiance and use of various chemical therapeutics and water borne disinfectants. Here we present a low dose hydrogen peroxide (H2O2) water hygiene practice tested on a commercial model trout farm. The study included application of H2O2 in a separate biofilter section and in the raceways with trout. Peroxide addition to the biofilter (C0 = 64 mg H2O2/L) significantly reduced ammonium removal efficiency (0.13 vs. 0.60 g N/m2/d) and nitrification partly recuperated within 7 d. Nitrite removal after H2O2 addition was only slightly impaired and no build-up of either ammonia/ammonium or nitrite was observed in the system. Application of H2O2 was rapidly degraded and caused substantial release of organic matter from the biofilter and hence increased the water flow and improved the hydraulic distribution through the biofilter. Low concentration H2O2 of about 15 mg/L was obtained in the raceways for three hours with temporarily disconnected biofilter sections, until H2O2 levels were <5 mg/L and considered safe to re-introduce to the biofilter sections. H2O2 addition in the raceways appeared to improve the water quality and did not affect the fish negatively. The study illustrates the options of using an environmental benign, easily degradable disinfectant and challenge the dogma that hydrogen peroxide is not suitable to recirculating aquaculture systems due to the risk of a biofilter collapse.

► Full scale test and application of H2O2 on a commercial model trout farm.
► Step-by-step approach including characterization of biofilter nitrification capacity before and after H2O2 application (analytically verified).
► Beneficial environmental and hygiene aspects of the reported H2O2 application.