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Title: Evaluation of ozonation on levels of the off-flavor compounds geosmin and 2-methylisoborneol in water and rainbow trout Oncorhynchus mykiss from water recirculation aquaculture systems

Author
item Schrader, Kevin
item DAVIDSON, JOHN - Freshwater Institute
item Rimando, Agnes
item SUMMERFELT, STEVEN - Freshwater Institute

Submitted to: Aquacultural Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2010
Publication Date: 5/25/2010
Citation: Schrader, K., Davidson, J.W., Rimando, A.M., Summerfelt, S.T. 2010. Evaluation of ozonation on levels of the off-flavor compounds geosmin and 2-methylisoborneol in water and rainbow trout Oncorhynchus mykiss from water recirculation aquaculture systems. Aquacultural Engineering. 43:46-50.

Interpretive Summary: Common “off-flavors” that can occur in rainbow trout raised in water recirculation aquaculture systems (WRAS) are “earthy” and “musty.” The effect of the low-dosage addition of ozone to the WRAS culture tank water on levels of the compounds responsible for earthy and musty off-flavors was studied. It was determined that low-dosage ozonation of culture water was not beneficial in reducing levels of the common off-flavor compounds in culture tank water and in the fish flesh.

Technical Abstract: Common “off-flavors” in fish cultured in water recirculation aquaculture systems (WRAS) are “earthy” and “musty” due to the presence of the off-flavor metabolites geosmin and 2-methylisoborneol (MIB), respectively. Previously, ozone addition has been applied to WRAS at relatively low doses to break refractory organic molecules (i.e., reducing color), micro-flocculate fine particulate matter (i.e., increasing solids removal), and oxidize nitrite to nitrate, but the effect of ozone addition at these dosing rates on levels of off-flavor compounds was unknown. Ozonation has been used in municipal drinking water facilities to reduce the levels of these compounds, to improve water taste, and subsequently reduce consumer complaints. In this study, the effects of ozone addition to the inlet water of the WRAS culture tanks on levels of geosmin and MIB in the culture water and fish flesh was evaluated. Water and rainbow trout (Oncorhynchus mykiss) samples were obtained twice after maximum feed rates were reached during a 6-month growout period. Results indicated that ozone addition to maintain an oxidation reduction potential of 248 mV (< 1µg/L of ozone residual) did not significantly reduce levels of these off-flavor compounds in the water and fish flesh, though it did significantly improve culture tank water quality. Higher dosages of ozone might be beneficial in removing geosmin and MIB in the WRAS water, but the inclusion of ultraviolet (UV) irradiation would be required to prevent mortality associated with ozone toxicity.