Aeration in fish farming

Our Norwegian distributor, Flow-Teknikk, assisted a customer involved in the oxygenation of salmon in open sea fish farming cages with an aeration solution containing automated and remotely controlled air flow controllers.
 

Aeration: supply of oxygen to water

Fish farming inside the Norwegian fjords is characterised by less circulation of water and warmer temperatures. Fjords protect the fish farms from excessive wave movements, but also provide ideal conditions for unwanted fish lice.
To prevent fish lice and other diseases on these farms, aeration into the fish cages is essential. Aeration, also called oxygenation, is the supply of oxygen to water. This can be done with air flow controller.  

Process solution

A set of multiple Bronkhorst MASS-STREAM™ D-6371 mass flow controllers is applied for the aeration, with one device for each fish cage. Each air flow controller supplies air in a range between 250 and 600 liters per minute. The air comes from a compressor and enters the flow instrument at a pressure of 6 bars.

The flow controllers are remotely controlled from a custom made human machine interface (HMI) on the customer's computer, using a PLC and the Modbus communication protocol. This computer is located in a command centre on land, and signals are sent via a mobile 4G network to a feeding raft in the sea between the fjords close to the cages. The compressor is located in the belly of the feeding raft, and the cabinet with the air flow controllers is on deck. The remote control from the command centre allows stopping aeration when they feed the fish, meaning that the people who control the feeding can also control aeration. This is a big step forward. Normally, they don’t want to use aeration at the same time as they are feeding.