Project aims to halve land-based mortality with new sensor
Development of real-time tools will reveal hidden risks in water chemistry before they become critical.
The Norwegian aquaculture technology company Searas is collaborating with fish farmers Baring Farsund and Mowi to develop and pilot a synthetic sensor for real-time monitoring of total inorganic carbon (TIC) in recirculating aquaculture system (RAS) facilities.
The goal of the project, which is funded by Norwegian seafood industry research funding bofdy FHF, is to reduce RAS mortality by 50%.
In RAS facilities, high levels of TIC can release large amounts of carbon dioxide (CO2) if pH drops, meaning that the water becomes acidic. This creates highly critical conditions for fish welfare and, in the worst case, can cause acute mortality. The risk is greatest toward the end of a production cycle and during crowding events.
Synthetic sensor
The project will develop and pilot a synthetic sensor for real-time monitoring of TIC. This will provide operators with trend insight, enabling earlier detection of risk and the ability to implement measures before levels become critical.
“Experience from RAS facilities shows that traditional measurements of CO2, O2 (oxygen) and pH are not enough. The water has an inherent risk linked to TIC. We are now developing not only a tool to measure this risk, but a framework to actively manage it,” explains Eldar Lien, project manager at Searas, in a press release. The same mechanism applies to total sulfide (TS) and the release of H2S (hydrogen sulphide).
Why TIC matters
CO2 is in close chemical interplay with pH and the water’s buffering capacity (alkalinity). TIC is a far more relevant parameter to monitor because it includes dissolved CO2, bicarbonate and carbonate. In practice, carbon can be “stored” invisibly in the system. When pH drops, CO2 is released, which in turn causes pH to drop further. This means that significant amounts of CO2 can be released into the water during, for example, stress events and lead to acute mortality. Rapidly falling pH also increases the risk of releasing the toxic gas hydrogen sulphide (H2S) from accumulated TS.
“What the operator needs is not just to ‘see a number’, but to see trends and understand what is building up in the water over time in order to get an early warning. TIC gives us a much better basis for decisions so we can manage water chemistry predictably,” says Lien.
Information to act on
The aim is to provide fish farmers with real-time insight, history and trends that make it possible to identify where and when risk is building up, and to act before it becomes an incident.
Searas says that its existing data platform already shows relationships between TIC, CO2, pH, salinity and temperature. This provides a better understanding of, among other things, degassing and carbon buffering in the system.
In the same data base, high-resolution measurements can also reveal where hydrogen sulphide begins to build up, how much is removed through degassing, and where stagnation areas occur in the plant.
The project also includes developing practical operating procedures to make the solution operational: thresholds/alarms and a framework for how risk should be handled in operations (action plans and protocols).
Sea water and fresh water
Baring Farsund operates a seawater OptiRAS facility delivered by Searas subsidiary Optiras, is contributing operational experience, production data, and operational input to the project. The project team includes, among others, Baring Farsund production manager Bjarte Sævareid and head of fish health Emil Høyesen.
Mowi is providing data from a RAS facility that uses freshwater.
Bjarte Sævareid at Baring Farsund said: “For us, this is about operational reliability. If we can see TIC building up early, we have a better basis for managing degassing and preventing stress and unwanted incidents - especially when the load is high.”