Recirculation technology

”Moving bed” bioreactor (MBBR) MBBR is a common denominator for a type of biofilters that employ small moving plastic parts that are kept in constant movement in the water in that air is blown into thebottom of the bio filter tank. On the surface of this material, bacteria will grow and form a bacteria coating – a biofilm. The bacteria in the biofilm use ammonium and organic compounds dissolved in the water as feed for growth, and this may be exploited to clean the water in the fish farming facility. A characteristic related to MBBR is that there is always good contact between the water to be cleaned and the biofilm that grows on the moving plastic elements. This is important for the bacteria to be able to exploit the dissolved compounds in the water efficiently and thus maintain stable and clean fish farming water.

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Efficient airing steps before the recirculation pumps
The aerator in the system is fitted in line after the biofilter and is designed to safeguard that there is equilibrium of gases in the water before it is returned to the fish tanks. The main function of the aerator is to remove CO2 . This is efficiently performed in that water and air come in to contact with each other in an airing medium. Water trickles down through the airing medium while air is blown in from below and flows up in the medium. This is called counter-current airing and this is where the ratio of air and water is controlled. The volume of air that is supplied, is 5-10 times the volume of the water that passes in the same period of time. This secures very efficient airing. It is favourable that as much air as possible is blown into the aerator in proportion to the volume of water. In order to obtain this effect, it is important that the aerator is clean and free from deposits and fouling at all times.

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Removal of particles
Particles in the form of excrements and remains of feed must be removed as soon as possible from a recirculation system. In KUBE®start, this is facilitated by securing good hydraulics in the fish tanks and the use of dual discharge. Excrements and feed spill are sedimented against the bottom of the tank and are discharged through a bottom strainer together with 15 % of the water in the tank. The remaining water, which is relatively particle free, passes out though a side discharge pipe. The water from the bottom strainer contains quite a lot of particles and is brought to a particle separator in which the particles are sedimented to a coat of organic sludge. The overflow water from the particle separator and the side discharge pipe is brought to a discharge pipe which directs the water to mechanical cleaning in a micro sieve with a mesh width of 40 μm.

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Cooling / heating system
KUBE®start is supplied with an integrated heat pump that is fitted close to the water treatment system. The heat pumps are reversible and are able to cool/heat the water depending on the desired temperature in the fish tanks. Control and monitoring is integrated in the PLC system. The heat pump is dimensioned for water temperatures between 1 – 21 °C, with 10 °C decrease and increase of the water temperature within 48 hours. The water’s theoretical time of replacement is normally about 3 days, i.e. with a supply of 40-50 litres of fresh water per minute.

UV treatment UV light may be used to inactivate micro organisms and pathogenic
bacteria in the water. UV light attacks the micro organisms’ hereditary material (DNA and RNA) and makes them unable to reproduce. UV lamps are available as low and medium pressure lamps. Medium pressure lamps provide a broader spectre of light than low pressure lamps and are thus more efficient in removing pathogens. By using medium pressure lamps, the micro organisms will not be able to repair the damage they sustain through UV treatment and the removal of the micro organisms will thus be permanent. KUBE®start is equipped with a medium pressure UV system that may be employed for the whole or parts of the water flow. This unit may vary the intensity of the UV treatment depending on variations in the quality of the water and has a built-in cleaning system that makes sure the lamps are kept clean.

Plug & Play The KUBE®
Systems are made up of prefabricated modules consisting of reactor, tanks and
pipelines in polypropylene, a material that has a long service life. Polypropylene is also resistant to chemicals and corrosion, as well as easy to clean and disinfect. The CompHatch® and KUBE® systems are water tested and quality assured before delivery.