Geosmin removal in Recirculating Aquaculture Systems (RAS)

Through decades in the aquaculture industry, there has been a lack of solutions for the expensive and comprehensive problem concerning Geosmin in water. Read further to explore the solution for Geosmin removal.

What is Geosmin and why is it a problem?

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FIGURE 1 – TYPICAL LAYOUT OF A RAS CULTURE SYSTEM

Geosmin and Methyl-Isoborneol (MIB) are naturally occurring compounds which are commonly found in the fish production of RAS (Recirculating Aquaculture Systems). Both substances accumulate in the fat tissue of the fish which can lead to a muddy taste from the fish. This leads to high economic losses every year for the aquaculture industry caused by prolonged production times. This is due to the need of off-flavoring the fish in purge tanks and additionally by the rejection of produce by the fish refining companies.

The Geosmin mitigation challenge

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FIGURE 2 – MODEL PREDICTED BUILD-UP AND LEVELS OF GEOSMIN IN RAS SYSTEMS WITH LOW- AND HIGH GEOSMIN SYSTEM FORMATION RATES

As of today, the usual method to remove geosmin from fish is by placing them into large high purity water tanks that are rich in oxygen. Doing so, the geosmin from their bodies get transferred to the water until it reaches equilibrium. However, this is a relatively costly method to ensure proper removal, as large quantities of pure water is required. In addition to this, the purge process adds on average an extra 10 days of fish delivery time, required for the geosmin to be reduced to limits of 5ng/L.

Research-based Geosmin assistance

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FIGURE 3 – MODEL PREDICTED CONCENTRATIONS OF GEOSMIN IN FISH AND WATER DURING OFF-FLAVOURING IN THE PURGE TANKS

The ULTRAAQUA UV research department has first-hand experience in solving and documenting geosmin control. The most optimal strategy concerning removing geosmin is to avoid or minimize the concentration of geosmin in the culture tanks, thus minimizing the need for off-flavoring in the purge tanks further on. Our R&D engineers and chemists have developed quantification tools to model and predict geosmin formation rates in RAS systems. The results of the different scenarios can then be used to make decisions regarding how to best implement a geosmin mitigation strategy.

Solving the Geosmin issue

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FIGURE 4 – DEGRADATION OF GEOSMIN IN RAS PROCESS WATER BY UV/H2O2 AOP PROCESS IN ULTRAAQUA MEDIUM PRESSURE UV REACTOR

Our consultants are able to assist in optimizing the plant architecture and management strategies to reduce geosmin formation. Additionally, ULTRAAQUA offer equipment to remove accumulated geosmin. The optimal solution typically varies from site to site depending on local characteristics. Often the optimal solution involves ULTRAAQUA AOP systems for combined chemical oxidation and photolysis breakdown. It is important to note that due to RAS intenseness, the multiple processes involved and variation in farm management makes each case sensitive and different requiring thorough investigation.

If your RAS processes are hindered by Geosmin concentration, you are very welcome to contact us at sales@ultraaqua.com or use the contact formula below.