Danfoss technology reduces energy consumption in salmon industry with 50%

Sea lice are a naturally occurring parasite, abundant in the ocean, that use salmon and trout as hosts. They also represent a tough  challenge to Norway's salmon  farms, where they easily penetrate the net pens where salmon grow and attach themselves to the fish. Large infestations can result in damage and mortality, and all sea lice on salmon must be removed  prior to sale.

The various treatment methodologies, including chemicals, cleaner fish, and thermal treatments, all have their advantages and disadvantages. One new treatment to remove sea lice from salmon, developed in Norway, uses a technique adapted from Mother Nature: when salmon leave the oceans to spawn in freshwater rivers, sea lice, which cannot survive in low-salinity water, naturally detach.

"Temporarily moving farmed salmon into freshwater is a simple, natural way to remove sea lice," explains Bjørn Dörum, director at Enwa Water Technology. "What's not so simple is generating fresh water at sea in quantities large enough to treat millions of salmon efficiently. That's where we come into the picture."

Enwa worked with DESS Aquaculture Shipping (DESS Aqua), a leading provider of vessel operations for the aquaculture industry, shipbuilders at Artic Group, and ship designers at Seacon to develop a new type of live fish carrier equipped with SWRO technology to provide the freshwater to delouse salmon at sea. Capacity had to be large enough to treat tons of salmon at a time, and energy efficiency had to be good enough to pass Norway's strict environmental regulations.

DESS Aqua contracted two new large well boats from Norway’s Arctic Group shipbuilders, each 76 m long and 15 m wide and with capacity for freshwater production of 6000 m³ per day. Enwa worked closely with DESS Aqua, Artic Group and SEACON to develop an SWRO plant powerful enough to produce 6000 m³/ day yet compact enough to fit into the ship’s bow, and so energy efficient that it requires 50% less energy than comparable SWRO
solutions.

Each SWRO plant  contains 3 Danfoss APP 86 pumps and 6 iSave 70 energy recovery  devices. According to Dörum, Enwa selected Danfoss pumps and ERDs for their reliability and energy efficiency, but also because the two companies’ R&D departments share the same passion for innovation and energy efficiency. “Enwa has worked with Danfoss for many years on a variety of innovative projects, and our R&D teams know their R&D engineers quite well. If we have a challenge, they help us solve it,” says Dörum.

Aqua Kvaløy was built in 2019 and operates in Norway for Mowi Norway. Aqua Tromøy completed construction in 2018 and operates in British Columbia, Canada for Mowi Canada West.

Diane Morrison, Mowi Canada West’s managing director, has called Aqua Tromøy a “game-changer”. “This vessel is on the cutting edge of aquaculture technology and is a crucially important tool in our integrated best management strategy allowing treatment with both freshwater bath and hydrogen peroxide, two sea lice treatment methods encouraged by the Aquaculture Stewardship  Council,” Morrison has stated. “Aqua Tromøy dramatically enhances Mowi Canada West’s ability to proactively manage our fish health in an environmentally friendly manner.”