The Mowi close containment smolt facility in Steinsvik was built by Krüger Kaldnes without an RAZONE treatment system of their process water. Steinsvik is ideal location to test a newly develop two phase ozone reactor tank- followed by a skimmer- system. The product of the Ålesund based company Normex is called RAZONE WATER CLARIFIER. The innovative approach based on preliminary findings to prolong the ozone exposer time in the RAS water through an additional reactor tank for a later so-called micro flock production that can be removed by the sea-/fresh- water “skimmer system” which is different build to a common protein skimmer that been normally only used in seawater. The ozone system was installed to the Smolt unit of Mowi Steinvik to treat around 10% of the reuse water.
In this project water quality and fish welfare was evaluated monthly over 3 production cycles in in Mowi Steinsvik. The first cycle was without an installed RAZONE system. The second cycle was done with a relative conservative Oxidation-reduction potential (ORP) that is used as a proxy of ozone dosage of around 280 mv and the second with around 300 mV.
The water quality obviously become clearer using ozone in the production sending water as bypass through the RAZONE system. Turbidity, color, Total suspended solids (TSS) and Total organic carbon (TOC) are significantly reduced. The reduction is even viable with normal eyes comparing the 3 smolt production cycles. The production can be influenced by abrupt appetite loss in fish. Feed spill events and decreasing water quality when the fish stop eating where highly reduced using the RAZONE system. The automatic feedback loop regulated through 2 OPR probes works secure and stabile.
Nitrite, Germ count, Copper, zinc, and cadmium reductions could be measured just directly behind the RAZONE system. If the 10% treated water is diluted with the untreated process water it is more difficult to detect smaller changes in these variables. Gill histology and welfare score could not detect any negative effect through the RAZONE system to the fish under the given conditions. However, it could be recognized that the smolt quality increased, especially in the last test run. The subjective scoring system made it difficult to provide a solid answer if the welfare status increased but it could be seen that the fin quality increased significantly in the last test run.
In summary using the RAZONE system provided healthy smolts as well as bettering and stabilizing the water quality during the production cycle.