Water treatments and systems
Land and sea Fish health in a pen or a landbased farm is dependent on good water treatment
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arlier this year, aquaculture technology specialist AKVA started work on its biggest ever contract – a massive land-based salmon farm Ningbo, near Shanghai. AKVA is building the recircula�ng aquaculture system (RAS) for Nordic Aqua Partners, which will be running the facility. It is planned to produce 8,000 tonnes of salmon in 2026 and the first phase alone will have a 4,000 tonne capacity. Ningbo is not the only large RAS project currently under way. For example, in April it was announced that Sande Se�efisk had signed a deal with water treatment specialists Sterner AS, for the RAS for a large smolt and post-smolt plant in Gloppen, south-west Norway. Meanwhile, Israel’s AquaMaof Aquaculture Technologies is helping to build a massive landbased farm for Proximar Seafood near Mount Fuji, Japan. While some land-based farms use a flow through system, these larger projects all use some form of RAS. Jacob Bregnballe, Sales Director, Land Based Salmon Projects with AKVA Group, explains: “Flow through works well only in certain loca�ons. In some sites in Iceland, for example, there is rela�vely warm, clean water which can be used for flow through, and also some parts of Norway. “I know the headaches you get with flow through – it’s a pain if the water is not perfect. Few places have clean water all year round and a storm can mean you get weeds and mud.” “We go for clean water technology because salmon live in clean rivers.” The classic RAS setup includes a mechanical filter, a biofilter which removes ammonia and a degassing process, removing CO2 which is also excreted and is harmful to the fish, before the water is returned to the tanks. It’s a constant
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process and down�me while fish are in the tanks would be hazardous. Bregnballe says that AKVA prefers to use biofilters using fixed-bed technology, in contrast to a moving-bed setup, in which the biofilters move in the water. The fixed-bed approach is preferred because this way the biofilter can remove micro-par�cles in the water as well as its main func�on, nitrifica�on (conver�ng ammonia excreted by the fish into nitrites, which are not harmful). He adds: “Micro-par�cles are a hazard to the fish because they can get into the gill filaments.” AKVA also uses an ozone process to safely disinfect the water and this
Above: The land-based salmon farm Ningbo Below: Cameron Kerr with compressor
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07/06/2021 15:22:58
