Development and validation trace geosmin and 2-MIB detection in seawater: Application to zeolite and photocatalytic treatment in marine RAS water

Abstract

Taste and odour compounds such as geosmin (GSM) and 2-methylisoborneol (2-MIB) are a major challenge in marine recirculating aquaculture systems (RAS) because they are occur at trace ng/L levels in the water, accumulate in fish flesh and cause strong earthy off-flavours that reduce customer satisfaction and perceived product quality, while remaining difficult to remove and to measure reliably. This thesis addresses a combined analytical and treatment gap by developing and validating a GC-MS method for trace-level GSM and 2-MIB detection in seawater and applying it to evaluate zeolite-based adsorption and photocatalytic treatment options in marine RAS water. A headspace solid-phase microextraction GC-MS (HS-SPME-GC-MS) method was developed, optimized and validated for artificial and real seawater matrices with a target detection limit below 10 ng/L. The final conditions used SIM mode, an internal standard, 3 g NaCl in 10 mL samples, 60°C and 30 min incubation, and 15 min extraction, achieving linear calibration with R² > 0.99 and limits of detection below 10 ng/L for both compounds. Systematic experiments revealed that matrix composition, organic content, competitive sorption on the fibre, incomplete SPME enrichment and analyte instability all significantly affected performance. Using the validated method, batch experiments in artificial seawater at 1000 ng/L compared powder zeolite-Y, an immobilized TiO₂-zeolite coating with and without UV, and UV alone. Powder zeolite-Y achieved rapid and near-complete removal (about 95% for 2-MIB and 99% for GSM, with capacities ~ 7.5 ng/mg), while the TiO₂-zeolite coating with UV initially gave ~97-98% removal but declined on reuse. Overall, the work shows that trace-level GSM and 2-MIB in seawater are challenging to manage because of low concentrations, volatility and SPME limitations, but that a carefully controlled HS-SPME-GC-MS method combined with zeolite-based adsorption provides a practical basis for monitoring and reducing these off-flavour compounds in marine RAS water.