ADVANCED OXIDATION PROCESSES FOR REMOVAL OF OFF-FLAVOUR COMPOUNDS IN RECIRCULATING AQUACULTURE SYSTEMS (RAS)
Recirculating aquaculture systems (RAS) often experience accumulation of off-flavour compounds, notably geosmin and 2-methylisoborneol (MIB). The complexity and variability of both the RAS system and its water matrix, including organic matter and salinity, challenge the effective design and application of treatment technologies for off-flavour control.
This research demonstrates advanced oxidation processes (AOPs) for the removal of geosmin and MIB in RAS. A laboratory-scale comparative study was conducted using water from a commercial salmon RAS growout system to assess the degradation of geosmin and MIB using UV/H2O2, O3/H2O2, vacuum-UV, and ozone pre-treatment followed by vacuum UV. The laboratory results were used to derive degradation kinetics and compare treatment performance under realistic RAS matrix conditions. Selected AOP configurations were subsequently tested at pilot scale to verify the laboratory findings.
A mechanistic mass-balance model was developed to describe geosmin and MIB dynamics in RAS growout and purge tanks and to enable application across different system designs. The model represents compound production, distribution between fish and water, and hydraulic exchange, and incorporates water-treatment from the laboratory- and pilot-scale experiments.
The model allows sizing and operational assessment of AOP water treatment to reduce geosmin and MIB in water and fish. Depending on the case, treatment can be applied in growout to prevent offflavour and avoid depuration, increasing capacity and avoiding weight loss. Alternatively, treatment during depuration can reduce purge time and thereby minimize weight loss.
Figure 1 Comparative test of four advanced oxidation process (AOP) for degradation of geosmin and 2-methylisoborneol (MIB) in commercial salmon RAS water: UV/H2O2, O3/H2O2, vacuum-UV (VUV), and ozone pre-treatment followed by vacuum-UV (VUV). Water concentrations are shown as a function of increasing dose.