Seeking better water quality with RAS

The Razone water treatment solution developed by Ålesund-based Normex to provide improved water quality and fish health in recirculation aquaculture system (RAS) plants is now being tested at the Mowi Steinsvik smolt facility in Volda local authority. Being conducted in cooperation with scientists from the Nofima food research institute, this project will report its conclusions around the end of 2020. 

One of the biggest challenges when raising fish in recirculation systems is the increased quantity of particles, which can reduce water quality and thereby fish welfare as well as causing sedimentation in piping and sumps. 

Razone treats water in a sidestream using a two-stage process. According to Normex, it removes microparticles, micro-organisms and micropollution and optimises water quality – yielding clearer water, improved fish health, better biosecurity and enhanced fish welfare. 


Normex installed the test facility at Mowi Steinsvik in May 2020. Preparations and testing will be pursued over the coming summer and autumn. 

During this period, Nofima will compare two independent smolt lines which have the same size category, density and biomass, in the same MowiSteinsvik department, with and without the use ofRazone.  

The research and development project is being supported by Innovation Norway through an innovation contract with Normex and Mowi as the pilot customer. 

Very important 

“We have great faith in this project,” says operations manager Kjell Arne Sætre at Mowi Steinsvik. “Water quality is very important for us. The tank environment at our plant is generally good, but there’s always room for improvement. 

“The results we’re hoping for cover removing more of the small particles, obtaining clearer water and securing even better conditions for the fish.” 

Microparticles in the water provide a growth foundation for fungi, viruses and bacteria, which can affect fish health. The Razone system is intended to remove a larger number of such tiny particles than can be achieved with existing solutions 


The Razone system comprises two tanks. Raw water from the RAS is first led to a contact tank via a sidestream, where ozone – a sustainable treatment agent – is added and oxidation occurs. That clears the water and removes colorants, while getting microflocculants to form. 

“Adding ozone causes the microparticles to clump together, making it easier to remove them,” explains Normex CEO Stig Johansen.  

The water then flows to a process tank where tiny microbubbles are added to push the microparticles to the surface as a layer of scum or sludge. This is skimmed off and taken to the existing RAS sludge treatment facility, with the cleaned water returned to the tanks. 


Mowiand Nofima are taking water samples in accordance with plans and guidelines from Nofima, which will evaluate the findings when this phase has been completed. The partners expect to be able to say something about the effects along the way, but final results will first be available early next year. 

“Our main aim is to establish whether Razone improves water quality,” observes innovation coordinator Per Brunsvik at Nofima. “Testing will investigate various factors, such as particle quantity, nitrogen compounds and metals in the water. 

“We’ll also be checking the fish to see whether the process affects them, with particular attention being paid to the gills. These are sensitive.” 


Mowi Steinsvik is keen to see Razone’s effect, and will participate in the testing this summer with Nofima. Sætre finds it very gratifying that the company can help to develop new technology on behalf of the industry. This is the first time it is trying an ozone-based system. 

“In addition to even clearer water and better tank conditions for the fish, we hope Razone can help to reduce the need for filter capacity at our facility,” he says. “We may perhaps also be able to use this solution to disinfect the RAS.” 

Normex is already experiencing great interest in its system from the fish farming industry, Johansen reports.  

“We see big opportunities for Razone. Land-based aquaculture is expanding for both smolt and grow-out fish production. A number of fish farms are now awaiting the results of this project.” 

See our new Aquaculture brochure

See our new Aquaculture brochure

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