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Aquaculture - RAS system

Kaiserzander - Germany

A new high-tech recirculating aquaculture system (RAS) for pikeperch, KAISERZANDER, was built in the German city of Porta Westfalica by the aquaculture specialists of glammeier + john aquakultur GmbH & Co. KG.

The planed RAS system has a total capacity of approx. 2.700 m3. In the first step, the so called first street was realized with a volume of 350 m³ in total. The system consists of small tanks for small fish, medium and big tanks. The fish will be sorted (depending on their size) and transferred into the next bigger tanks.

The young fish (fry) arrive at the facility with a weight of approx. 10-15 g. They grow to an average size of 1.000 g.

The annual production of the plant is approx. 100 t of fish.
The feeding is carried out automatically several times a day, but the aquaculture specialists balance and control the amount of fish food to prevent overfeeding which would result in a contamination of the water.

The lighting as well as the water temperature in the aquaculture system is being controlled to ensure the best conditions for the fish.



This aquaculture system is designed as a recirculating aquaculture system (RAS), which has a water exchange of 3 to 10% per day. The whole water is being treated within a biofilter and recirculated back into the fish tanks. Besides that, KAISERZANDER has its own facilities for treating the wastewater from the system. The huge amount of water, which is recirculated back into the fish tanks, sets several requirements for the quality of the water to ensure a suitable environment that maximizes fish growth and health. Some important parameters for the health of the fishes are ammonium (NH4), nitrite (NO2), nitrate (NO3), the pH-value, chemical oxygen demand (COD) and the oxygen content (DO) in the water.
The effluent from the fish tanks into the water treatment system varies with, for example, the amount of fish and food used. This sets high requirements for the treatment of the water.


To deal with the demands of a low COD and ammonia content in the recirculated water, KAISERZANDER uses the biofilm carrier media Mutag BioChip™ for the biological treatment of the water in an MBBR (Moving Bed Biofilm Reactor). This reduces the COD and the nitrification process converts the ammonia in the water into nitrate. A part of the water runs through a denitrification stage where the nitrate concentration is being reduced through the denitrification of nitrate into nitrogen gas. By using the Mutag BioChip™, it is possible to attain a higher performance at lower filling rates due to the unique design and performance of the BioChip.

The treatment of the wastewater of the RAS consists of an MBBR combined with a denitrification step by using Mutag BioChip™.


Beneficial cooperation
As a leading manufacturer of carrier media for water and wastewater treatment, MUTAG takes pride in ongoing investigation and development of the product Mutag BioChip™.

MUTAG has a unique cooperation with KAISERZANDER, established by their interest in creating the optimum conditions for the fish and MUTAG’s drive for optimization of its product’s efficiency. By this, MUTAG had the opportunity to install a pilot plant next to the system where the water is being treated for recirculation. From the pilot plant’s results, it is possible to investigate on the function of the product on-site and to continue the operation of modified BioChips.

Furthermore, during the start of the aquaculture operation, the close cooperation has been the foundation for continuous observation and optimization of the MBBR stage(s) and the denitrification systems.

With the use of Mutag BioChip™, KAISERZANDER has obtained the water quality needed with concern to COD, ammonia, nitrite and nitrate concentrations for recirculating water in the fish tanks and provided healthy water conditions for their fish.


Mutag BioChip™ in the biofilter of the RAS system (denitrification stage)

Mutag BioChip™ in the biofilter of the RAS system (denitrification stage)

Aquaculture fish tanks at KAISERZANDER

Aquaculture fish tanks at KAISERZANDER

Wastewater treatment by means of Mutag BioChip™

Wastewater treatment by means of Mutag BioChip™