The challenge

The Innhavet RAS plant has 34 fish tanks of different capacities (350 to 1’000 m³) in 5 main separate sections. Each section is independent from the others and includes its own complete water treatment system in a semi-closed loop (98% recirculation + 2% make-up water). The brackish water from the fish tanks first flows by gravity to a rotating drum filter for the removal of main suspended solid particles. It then falls in an MBBR (Moving Bed Biofilm Reactor) for TAN (Total Ammonium Nitrogen) reduction. After passing through a countercurrent degasser for the stripping of nitrogen and carbon dioxide, the treated water is finally pumped to some head tanks prior to oxygenation and returned to the fish tanks.

In each fish tank, the water is totally renewed every half an hour. The well-being of the smolts is highly dependent on a constant flow of water through the facility. The reliability of the recirculation pumps is, therefore, of paramount importance.

High overall energy performance of the RAS plant means better environmental footprint and reduced operating costs. Consequently, the main components of the water treatment loops must have top-class efficiencies, particularly the recirculation pumps.

The solution

As a long-term supplier of equipment (pumps and turbines) in other Nordlaks plants, Sulzer was involved at an early stage of the new project. In collaboration with the Momek Group, a large industrial service provider in Scandinavia, the pumps were carefully selected, not only to fulfil the requirements during the warranty period, but to run optimally and economically during the whole lifetime of the site. For the recirculation of the brackish water, 50 AHLSTAR and BE process pumps in duplex material have now been installed and are operating continuously. In addition, 5 VUPX submersible propeller pumps are used on intermittent duty when the fish tanks are emptied during the transfer of smolts.