Water treatment in RAS systems

A major technological shift in a 344 million annual production of Atlantic salmon smolt is occurring in Norway. Land-based flow through systems are being replaced by recirculating aquaculture systems (RAS). These sophisticated systems have a low water usage, no fish escapees, and a controlled production environment which is optimal for fish production.

RAS consist of a series of water treatment units, including a biofilter to treat the water and reuse it.

A new challenge

However, the innovative nature of RAS poses a new challenge on how to disinfect the water without producing an adverse impact on the salmon’s health and welfare, and biofilter performance. Further information on how to implement a more efficient and operational disinfection strategy is needed.

There are several strategies which could potentially be used for water treatment in RAS, but their impact on fish health, welfare and growth needs to be documented before applying them to an industrial scale. Likewise, the equilibrium between keeping unwanted bacteria and virus levels low and functional bacteria in the biofilter requires the development of an operational method to monitor the biofilm activity.

The RASHealth project aims

• To improve water treatment methods using ozone (O3) and peracetic acid (PAA).
• To increase biosecurity by adopting disinfection strategies that consider the disease vectors and reservoirs of pathogens.
• To document PAA’s effect on Atlantic salmon health, welfare and growth, and to evaluate two different methods.
• To develop and test a new quantification method for biofilm activity during daily operations.

The project is expected to contribute to the standardisation of water disinfection with an impact on the future design and performance of RAS. Ultimately, RASHealth will directly contribute to the sustainability of Norwegian aquaculture by developing a food production system that efficiently produces nutritious food with reduced environmental impacts.