Removal of the off-flavor compounds geosmin and 2-methylisoborneol from recirculating aquaculture system water by ultrasonically induced cavitation

摘要

With its high economic impact, off-flavor in fish is still one of the most serious problems in the aquaculture industry worldwide. Until now, the highly cost- and time-intensive, as well as capacity demanding depuration procedure by moving the fish to clean and odor-free water for a certain time prior to harvest is the only reliable way to counteract off-flavors in aquaculture. Alternative strategies and processes for efficient off-flavor prevention are still lacking. Hence, the aim of this study was to investigate the potential of ultrasonic water treatment to decrease the concentration of the relevant off-flavor compounds geosmin (GSM) and 2-methylisoborneol (2-MIB) in aquaculture water. Therefore, different water matrices, varying in their organic and inorganic load and composition (tap water, RAS fresh water, RAS sea water), were spiked with 2-MIB and GSM standard and subsamples of 250 mL were subsequently treated for 15 min using a lab-scale ultrasound transducer at 850 kHz. For verification samples from commercial RAS containing biogenic 2-MIB and GSM were treated equally. The effects of ultrasound frequency and salinity on the removability of 2-MIB and GSM via ultrasonic treatment were investigated by comparing the removal efficiency of high (850 kHz) vs. low (20 kHz) frequency ultrasound and by adding artificial sea salt (10 ppt) to different freshwater samples prior to ultrasound treatment, respectively.