Measuring environmental concentrations of hydrogen peroxide following bath treatment

Measurements of environmental concentrations of hydrogen peroxide following bath treatment at a Norwegian fish farming site was performed by using a flexible, robust and mobile measurement system covering multiple depths, ranging from 5 to 100 m. This system was supported by real-time current and dispersion modelling, making it possible to detect and track the hydrogen peroxide as it spread from the treated net pen. The collected data indicates a complex vertical behaviour of the bath water after the release of the tarpaulin, with hydrogen peroxide found both in the surface layer and at depth within the study area. Concentrations peaked in the upper 40 m near the net pen where the highest concentrations reached 300 mg/L, equivalent to a dilution factor of 5. A falling gradient of concentrations was found with increasing distance from the net pen. Numerical model simulations were used to support and gain further insight into the measured data. Experience gained in the present and in previous studies points also to potential improvements that can be incorporated in future studies, where particular attention should be paid to the near-field effects of the tarpaulin removal, as well as measurements of concentrations further downstream from the fish farm.