Norway develops nitrogen gauge for RAS

A FULLY automatic sensor that measures levels of nitrogen compounds in recirculated water has been developed by Norwegian research institute Nofima.
It is the first sensor specifically for aquaculture, with the sensitivity and accuracy that are required. Previous solutions have used technology from the water management industry, and have not been adapted for aquaculture.
The technology, developed with EU partners, is particularly valuable in recirculating aquaculture systems (RAS) for the measurement of the nitrogen compound nitrite. High quality measurements of water quality are crucial in such systems to ensure the welfare of the fish.
All recirculating aquaculture systems have a biofilter, which consists of micro-organisms that convert nitrogen based waste products to nitrites and nitrates.
High levels of nitrite and ammonia indicate that the biofilter is not functioning optimally. It is, therefore, important that the concentrations are continuously known to ensure efficient breakdown of potentially toxic nitrogen compounds in the water.
‘We must give the fish the water quality required such that they are comfortable and grow optimally – since consideration of their welfare is given highest priority,’ said scientist Jelena Kolarevic, who with colleague Bjørn-Steinar Sæther, she has led Nofima’s part of the work, which is a part of the EU project AQUAlity.
‘Our knowledge about salmon and its welfare and performance in recirculating aquaculture systems has enabled us to adapt the technology such that it is well suited to the biology of the salmon.’
AQUAlity is supported by the Seventh Framework Programme of the EU. The goal was to develop an open standardised technology platform for monitoring the quality of water in the process line.
Using this technology should reduce costs and the need for expertise of facility personnel, and should give reliable measurements of potentially toxic nitrogen compounds in aquaculture.
Nofima’s role in the project was to contribute expertise of fish needs and limits for various parameters of water quality, to test the prototype, and to evaluate how it can be further developed for use in RAS.
The work was carried out in the laboratory and at the Nofima Centre for Recirculation in Aquaculture at Sunndalsøra in Norway.
Also involved in the project was Dag Egil Bundgaard (pictured), who tested the prototype and helped integrate it into the whole AQUAlity system.
Nofima will present the system on October 22 during the Aquaculture Europe conference in Rotterdam, the Netherlands.