Recirculating Aquaculture System RAS

Recirculation aquaculture systems is a technology for farming fish or other aquatic organisms by reusing the water in the production. It can be operated either as an outdoor or an indoor system. The method can be used for any species grown in aquaculture such as fish, shrimps, clams, etc.

Freshwater, land-based RAS offer a viable alternative that enables flexibility in the location of your facility, reduces the expense and carbon footprint of transportation, and increases the supply of traceable, nutritious seafood farmed locally near the customer.

At CDEng we work primarily with RAS systems for fish farms. We work on the total system balance, optimizing and modernizing this technology to lower the costs, make it easy to operate and to increase its availability to the user (the fish farmer).

The application of RAS is growing rapidly in many areas of the fish farming sector, and the systems are deployed in production units that vary from huge plants, generating many tons of fish per year to small sophisticated systems used for restocking or to save endangered species. This is also the principle used in many aquariums – both at home and at marine centers.

Recirculation can be carried out at different intensities depending on how much water is recirculated or re-used. Some farms are super intensive farming systems installed inside a closed insulated building using as little as a few liters of new water per fish and year. Other systems are traditional outdoor farms that have been rebuilt into recirculated systems using a few thousand liters of added water per kilo of fish produced per year. A traditional flow through system for trout will typically use around 30 m3 per kilo of fish produced per year.

CDEng Aquaculture Solution

At CDEng & collaborators, we together have years of experience in water purification, fish farming, mechanical engineering and analytical chemistry. Our mapped-out facility relies on modern application of published design, industrial experience and biology/chemistry research. Our team is also available for consultant services within aquaculture.

Our design is land based salmonid farming with a long tradition in North America. Numerous research facilities have for decades published on salmonid farming. Fish behavior, water chemistry and growth patterns are well known and accessible for researchers worldwide. The land based miniatured facilities are many and yet to be engineered at large scale. The timing is right to combine knowledge and technology from various fields into cross-disciplinary engineering.

In our state-of-the-art RAS system for Arctic char, we have developed the following key aspects of operations for improved sustainability and optimized production:

  • Growth cycles and optimization
  • Feeding strategy
  • Tank design and flow dynamics
  • Optimized fish health - environment, stress, resting cycles
  • End of growth handling (grading)
  • Sustainability design
  • Human/technology interfaces (handling)
  • Process control strategy and systems
  • Sensor and control systems
  • Water chemistry
  • Water treatment
    • Filters
    • Biostages (nitrite/nitrate)
    • Chemical analysis
    • Aeration/de-CO2
    • Dissolved metal control (Fe, other metals, oxidants)
    • Bleed off balancing
    • Discharge treatment and effluent control
    • Sludge handling and management
  • Management strategies and technology for changes in supply quality