A nitrogen gauge for aquaculture
Nofima has developed in collaboration with European partners a fully automatic sensor to measure levels of nitrogen compounds in recirculated water.
It is the first sensor that has been developed 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.
Beneficial in closed-containment aquaculture
This technology is becoming evermore important since closed-containment aquaculture is being tested and becoming established. Recirculating aquaculture systems are used for closed-containment aquaculture on land, and high-quality measurements of water quality are crucial in such systems to ensure the welfare of the fish.
This sensor is particularly valuable in recirculating aquaculture systems for the measurement of the nitrogen compound nitrite. 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 break-down 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. 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,” says scientist Jelena Kolarevic. Together with colleague Bjørn-Steinar Sæther, she has led Nofima’s part of the work, which is a part of the EU project “AQUAlity”.
AQUAlity is supported by the 7th 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. The sensor in whose development Nofima has participated, in collaboration with Philips and other actors, is one of the deliverables of this project.
Tested and developed
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 such that it can be used in recirculating aquaculture systems. The work was carried out in the laboratory and at the “Nofima Centre for Recirculation in Aquaculture” at Sunndalsøra, where innovative technical personnel played a crucial role.
Dag Egil Bundgaard was one of them. Kees Bink, project manager from Philips research, describes Dag Egil’s contribution as follows:
“Bundgaard has very broad interests, a broad skill set, and a strong desire to innovate. This enabled him not only to test the prototype, but also to further develop it and to help integrate it into the full AQUAlity system. He communicated with developers in The Netherlands and managed to become as familiar with the device as the Philips technologists who had designed it.
Bundgaard and his colleagues subsequently transferred knowledge of the complete system to the consortium partner OxyGuard, and set up the system such that it could be demonstrated for the EU project management team.”
This is what the sensor measures
OxyGuard is now planning to take the prototype onwards towards commercialisation and sale to the aquaculture industry.
The sensor can continuously monitor water quality in recirculating aquaculture systems, and is a component of measurement equipment that measures eight parameters simultaneously. Facility personnel receive continuous on-line measurements of nitrite, total nitrogen compounds, pH, salinity, oxygen level, carbon dioxide level, total gas saturation and temperature. These levels can be read on a screen.
Nofima presented the system at the Nordic RAS workshop in Molde on 31 September, and will present it again on 22 October during the Aquaculture Europe conference in Rotterdam.