REX-M land-based Recirculating Aquaculture Systems (RAS) and partial RAS (PRAS) are characterized by species-specific layout (productive volume, water treatment), practice-oriented management (accessibility, control) and minimization of both investment (process technology, construction) and operating costs (low head design, hydraulic retention time).
Parallel connected circular, rectangular or D-End tanks are the standard for hatcheries (weaning, nursery) and small-scale RAS. This extends to production of fresh water eels and some perch-like fish. For large scale fish farming (on-growing, grow-out and broodstock) RAS expert Mahnke focusses unique system solutions:
- Habitat: Parallel connected Raceway Loops // Water depth < 2m
- Characteristic: Raceway Loop internal recirculation and degassing
- Species: Trout, charr, sturgeon (caviar), tilapia, HSB, prawn, catfish, carp
Circular Tank Twins
- Habitat: Two large Circular Tanks // Water depth > 3m
- Characteristic: Separate water supply for each individual fish tank
- Species: Trout, salmon, tilapia, barramundi, pangasius, carp
Any large-scale circular tank and raceway is equipped with dual-drain. Thus, both the sediment from the faeces pits and the dirt film on the water surface can be removed. Especially in circular tanks hydraulics can be adjusted to fish species and fish size. In raceways the habitat can be divided individually with the help of separating grids. In any case fish tanks of RAS can be taken from the system to be drained individually. Instead without piping the series-connection of raceways in partial RAS allows a most-efficient recirculation.
RAS are based on water transport and mechanical, physical, biological and chemical water treatment. By this RAS minimize water demand and realize optimal control of farming conditions. REX-M design and engineering is based on a proper production plan and is adapted to well-proven equipment of exclusive manufacturers. REX-M customers benefit from partner prices:
BIOLOGICAL WATER TREATMENT
Substances dissolved in water will be reduced by bacteria. Nitrification, meaning the elimination of fish toxic ammonia, is the bacterial oxidation of ammonium to nitrite (Nitrosomonas & Nitrospira) and nitrate (Nitrobacter). Nitrate either can be thinned out by exchange of water or can be reduced by bacterial denitrification.
REX-M partner for packings is Christian Stöhr GmbH & Co.KG:
PHYSICAL WATER TREATMENT
Aeration supplies fish and bacteria with oxygen and degas unwanted gases (e. g. carbon dioxide & nitrogen).
REX-M partner for diffuser systems is OTT System GmbH & Co. KG, REX-M partner for mechanical oxygenators is OOO Merke (LINN Gerätebau GmbH) and REX-M Partner for trickling tower degassing is Christian Stöhr GmbH & Co.KG:
- D-REX diffuser
- MAGNUM diffuser
- AIRREX carrier system
- LOXY mechanical oxygenator
- HEL-X trickling tower packings
Germs will be reduced by the exposure to UV-light.
REX-M partner for UV-systems is ULTRAAQUA A/S:
MECHANICAL WATER TREATMENT
Particular matter accumulates in the water during the production process. Settlers remove sediments. Microscreen drum filters remove suspended solids larger than 30 µm. Fine suspended solids will be controlled in submerged fixed bed reactors.
REX-M partner for microscreen drum filters is OOO Merke (FAIVRE Sas), REX-M partner for fixed bed packings is Christian Stöhr GmbH & Co.KG:
CHEMICAL WATER TREATMENT
Using ozonation reduces not only germs effectively. Moreover ozone boosts degradation of organic compounds (yellow substance → turbidity ↓) and increases both nitrite oxidation and redox potential.
REX-M RAS are characterized by their Low-Head-Design. Propeller pumps are most efficient to recirculate the water. Submersible pumps, volute casing pumps and filter pumps are utilized for small-scale RAS, bypass filter applications and sewage. High-pressure pumps are utilized for injection of ozone, backwashing of drum filters and transport of well water.
REX-M Partner for pumps is KSB AG:
- AMALINE propeller pumps
- AMAREX submersible pumps
- SEWABLOC volute casing pumps
- MOVITEC high-pressure pumps
Regularly REX-M is using frequency-controlled 1-ary side channel blowers for small, variable volumetric flow rates up to 500 m³/h and 250 mbar. Above rotary piston fans and 2-ary side channel blowers are applied.
REX-M partner for side channel blowers is Elektror airsystems GmbH and REX-M partner for rotary piston fans is Aerzener Maschinenfabrik GmbH:
PVC-U pressure pipes up to nominal size DN250 are suitable to transport water and air. PVC-U sewage pipes are available up to DN500. For water applications of larger nominal diameters REX-M is planning pipes made from Polyethylen or channels.
REX-M partner for PVC-U piping is LA.RE.TER. Spa:
PH-set point will be adjusted by demand-actuated supply of alkaline substances in form of lime and soda with help of dosing units. Denitrifying bacteria will be fed with carbon.
REX-M partner for dosing systems is sera GmbH: