Kaldnes™ RAS

Serving the Aquaculture Industry

For more than 20 years Krüger Kaldnes has supplied the aquaculture industry with solutions and technologies for high quality water treatment.

Krüger Kaldnes as a part of Veolia Water Technologies, comprising world class technical know-how and technologies for water purification. As such Krüger Kaldnes offers a wide range of solutions that can be tailored to meet the highest standards providing prime quality, energy efficiency and operational friendly water treatment systems.
Krüger Kaldnes provides a range of solutions and technologies to the aquaculture industry. Some of our well known technologies includes biological water treatment using the AnoxKaldnes™ MBBR process and solids removal using Hydrotech Drum filters. 

The core of our business is know-how and the drive to develop efficient and operator friendly methods for water treatment. This is often characterized by the fact that our solutions are very compact, has low operating costs and is adapted to our customers' individual needs.

The Solution
Efficient and Operator Friendly

Our solutions for the Aquaculture Industry include:

  • Recirculating Aquaculture Systems (RAS)
  • Treatment of intake water
  • Conditioning of water during production in flow through systems
  • Treatment of effluent water
  • Sludge treatment
  • Treatment of water and waste from fish abattoir and processing

Flexibility and Reliability


  • Particle control down to Nano filtration


  • Maintenance free
  • Peak load resistant
  • Specially adapted for each client

Aeration and oxygenation

  • Removal of both carbon dioxide and nitrogen
  • Maximum utilization of added oxygen

Reliability and operation

  • Smallest footprint possible
  • Operational friendly
  • No need for backflushing of the biofilter

Enviromental / sustainability

  • Reduced water consumption
  • Reduced energy consumption
  • Waste treatment
  • Improved feed utilization
  • Small foot-print

Flexibility and Reliability - The Underlying Technologies

Both salmonids and other species have proved to meet the highest quality when farmed in Kaldnes™ RAS systems.At first glance, increased growth rate (SGR) and high survival rate are obvious benefits. Furthermore, reduced stress and increased fish welfare are other advantages that Kaldnes™ RAS provides.

Kaldnes™ RAS meets the demand for flexible and reliable water chemistry. Sudden changes that may provoke potential harmful environmental factors, such as sludge accumulation are eliminated.

A central idea behind the Kaldnes™ RAS is low energy input. Therefore, head loss in Kaldnes™ RAS is kept to a minimum. Typical energy consumption rarely exceeds 2 kw/kg fish produced.

A costly input factor in intensive fish farming is pure oxygen. Kaldnes™ RAS therefore utilizes all available oxygen. Kaldnes™ RAS offer special low head oxygenating cones that ensures a full saturation with minimal pressure. Furthermore, excess available oxygen not consumed by the fish culture is utilized by the AnoxKaldnes™ Moving Bed biofilm reactor.

With proven fundamentals for more than 20 years, Kaldnes™ RAS takes fish farming to a new level!

The Fundament

AnoxKaldnes™ MBBR
The Moving Bed Biofilm Reactor (AnoxKaldnes™ MBBR) is our own proprietary technology, and the biological engine of Kaldnes™ RAS. The MBBR technology allows the microorganisms to grow on sheltered, surfaces inside moving, plastic carriers creating a continuous biofilm process without any risk for clogging and without any need for back flushing. Advantages like low head loss and high volumetric capacity make the process compact and well suited for treatment of large water flows. The process is very robust and easily operated with a minimum need for maintenance.

Hydrotech drum filters
Biomass from the AnoxKaldnes™ MBBR process, fish faeces and excess feed is efficiently separated with Hydrotech drum filters, another well-known Veolia Water Technologies' technology in the industry. The Hydrotech filters have a high hydraulic capacity, are easy to operate and provide predictable results. Typical mesh sizes are 40-90 micron, but can be delivered with mesh sizes down to 10 micron.