Measuring of efficiency for newaeration technology in fish farming.


On behalf of Alvestad Marine AS, IRIS has tested the company’s new technology for CO2 aeration of water. The test was carried out in the period April – August 2013 in the pilot unit of the product at the Marine Harvest hatchery facility at Kvingo. Alvestad Marine AS’ partner BioFarmSystems AS has taken part in the testing. The aerator is based on the counter flow principle in which the ratio between the water flow and the air flow may be controlled. The new aeration technology has a patented cleaning system which automatically keeps the aeration medium clean and free from fouling at all times. In this way, you will always obtain constant and predictable water treatment effect no matter the time of the year.

In the work so far, the emphasis has been focused on two issues:

  • The unit’s efficiency with reference to removing carbon dioxide (CO2)
  • The cleaning system’s efficiency with reference to removing fouling and
    particles in the aeration medium.

Removing of carbon dioxide

In a measuring in August, the concentration of CO2 was consecutively reduced from 10 mg/l to 2 – 3 mg/l; which means removal of 70 – 80 per cent at the water’s passage through the aerator; see the photo. A similar measurement in April presented a reduction from 8 – 9 to 4-5 mg CO2/l (40 – 60 % reduction). In both periods, the fish population in the tank in question was at its maximum just before delivery of smolt, but the temperature was 13.5 and 3.5 °C respectively. A contributing factor to the increased cleaning effect in August was a technical adjustment carried out during the summer. The pH in the water increased by 0.6 – 0.7 unit through the aerator as a consequence of reduced CO2 content.


Measured efficiency for the reduction of carbon dioxide through the Aerator at MNH, dept. Kvingo on August 5th 2013. The parallel aeration units are designated I and II respectively.

Cleaning effect fouling
Based on 5 months continuous operation, March – August, the system for automatic cleaning of the aeration medium seems to work very satisfactorily. The system is based on daily back flushing/stirring of the medium for 15 minutes per unit. On the basis of a visual inspection of the medium with individual components through the summer, only minor remains of organic particles and no visible fouling was recorded, see the photo. The maintenance of the aeration medium is clearly decisive for the high measured effect of CO2 removal in the