In the second project phase, I start with the technical planning of RAS and flow-through systems. My design and engineering is based on a reliable production plan, a proper layout and combination of process technology and is adapted to well-proven equipment of exclusive manufacturers.

My aquaculture systems are characterized by species-specific layout (habitat, water treatment), practice-oriented management (accessibility, control) and minimization of both capital expenditures (process technology, construction) and operating costs (low head design, hydraulic retention time).

As a freelancer, I don’t sell any equipment. You can buy by youself according to my information. I’m happy to support your technical purchasing department!

rex-m engineering


An aquaculture system is made up of the habitat, water throughput and water treatment. Layout or review of process technology particularly is based on species, feed amount and flow rate. I specify the equipment, i.e. the machines, tanks, basin installations, filter media, pipelines and fittings (air and water), in detail with help of tabular overviews, engineering drawings and process diagrams; off course system descriptions are an option too. My tabular information includes manufacturers, prices, dimensions, connections, capacity, power, hydraulics and consumption. In summary, I show the capital expenditure (Capex) and the operating costs (Opex) of the aquaculture systems.

Water treatment


Mechanical filtration

Sediment removal

Particular matter accumulates in the water during the production process. Any large-scale circular tank and raceway is equipped with dual-drain effluents. Thus, both the sediment from the faeces pits and the dirt film on the water surface can be removed. 

Suspended solids removal

Microscreen drum filters remove suspended solids. Smaller filter pore sizes increase the removal rate of TSS to a certain extent. Screen sizes below 60 µm no longer improve solids removal. My partner for microscreen drum filters is OOO Merke (FAIVRE Sas). In the context of end-of-pipe treatment sediments from drumfilter`s backwash water can be removed with settling tanks or belt filters.

Fine suspended solids removal

In rex-m RAS design fine suspended solids will be controlled in submerged fixed bed bio reactors (FBBR). For backwashing FBBR are equipped with air-flushing. Dewatering can be controlled perfectly due to very good accessibility of valves and pipes. My partner for HEL-X filter media is Christian Stöhr GmbH & Co.KG.

If hydroponics is included in the water treatment the expanded clay or the like should be sufficient for fine suspended solids control. Especially when operated with flood and drain technology. The latter boosts the mineralization of solids.

Biofilter

Nitrification

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). For nitrification and degassing I apply mainly moving bed bio reactors (MBBR). I plan the filling level of the MBBR at around 40%, so that a reserve of around 10% packings or 20% filter capacity is available. The generous dimensioning of the retention grids guarantees an accurate mixing of the filter media. Due to fine suspended solids control a branch current will be directed via fixed bed bio reactors (FBBR). Because of degassing trickling towers are connected downstream the FBBR.

Denitrification

Nitrate either can be thinned out by exchange of water or can be reduced by bacterial denitrification. A reasonable denitrification rate minimizes the average need for water supply and wastewater disposal to 40-80%. If necessary, the water supply can be further reduced by reusing the centrally biologically (denitrification) and chemically (phosphate precipitation) treated wastewater partly. 
My partner for HEL-X biocarriers is Christian Stöhr GmbH & Co.KG.

Physical treatment

Aeration

Aeration supplies fish and bacteria with oxygen and degasses unwanted gases as carbon dioxide. My aquaculture systems combine compressed air ventilationtrickling towers and oxygenation. Spare blowers are integrated in the aquaculture system design. Blowers must suck fresh air to avoid a CO2-short-circuit. Maximum carbon dioxide content for room air shouldn`t exceed 1500 ppm. Air exhaustion must be located best in the area of compressed air ventilation and trickling towers. My partner for HEL-X trickling pack is Christian Stöhr GmbH & Co.KG and for centrifugal fans for low pressure ventilation of trickling towers Elektror airsystems GmbH.

For compressed air intake I use D-REX diffuserMAGNUM diffuser and AIRREX carrier systems. Frequency-controlled side channel blowers are utilized for small, variable volumetric flow rates up to a pressure stage of 250 mbar. Rotary piston fans find a use in larger scale RAS. My partner for diffuser systems is OTT System GmbH, for side channel blowers Elektror airsystems GmbH and for rotary piston fans Aerzener Maschinenfabrik GmbH.

Oxygenation

So far enough my aquaculture systems make use of central low-head oxygenation. Pressure-free, mechanical oxygenators are suited for my flow-through systems. My partner for oxygenators is OOO Merke (LINN Gerätebau GmbH). Emergency oxygenation (LOX!) must start automatically in case of low oxygen, low level, low air pressure and dysfunction of pumps, of blowers and of electrical installation. 

UV disinfection

Possibly pathogenic bacteria will be reduced to a limit of approximately 10000 CFU/ml by the exposure to UV-light. Closed UV reactors will be integrated in the piping of small-scale RAS and in the hatchery. For large flow rates open channel UV systems find a use in rex-m RAS design. My partner for UV-systems is ULTRAAQUA A/S.

Chemical processes

Ozonation

Using ozonation reduces not only germs effectively. Moreover ozone boosts degradation of organic compounds as yellow substance. By this turbidity will be decreased significantly. On top ozone increase both nitrite oxidation and redox potential. 

In rex-m RAS design the outflow from the denitrification, which is heavily contaminated with germs, is completely ozonized. I provide pressurized tanks for the ozone reaction. The ozone is introduced under high pressure (2 bar) via an injector in the bypass to the ozone reactor. The drain from the ozone reactor feeds the fixed bed bio reactors in order to optimize their oxygen supply and retention of fine suspended solids. My partner for ozone generators is Xylem Water Solutions Deutschland GmbH.

pH stabilization

Hydrogen ions are released during nitrification to be more precise during the conversion of ammonium to nitrite. In rex-m RAS design the pH-value will be adjusted by demand-actuated dosing of alkaline substances in form of lime and soda. 

With the help of the denitrification process the pH value can be largely stabilized to compensate for nitrification. Denitrifying bacteria must be fed with carbonic, organic compounds in the form of molasses, ethanol, methanol, glycerin or acetol. These bacteria process carbon to carbon dioxide and water by consuming chemically bound oxygen.

My partner for compact tank dosing units and compact dosing systems is sera GmbH.

Water recirculation


Pumps

My large-scale RAS are characterized by low-head design and application of vertical propeller pumps. In addition to it Raceway Loops© rex-m are equipped with mammoth pumps for hydro-pneumatic water transport. Horizontal propeller pumps realize water recirculation and therefore adequate current in my large-scale flow-through systems, which more or less don´t show any geodetic head. Submersible pumps and dry positioned pumps are utilized for medium-head applications in small-scale aquaculture systems, bypass-filter and sewage plants. 

Function of recirculation pumps must be monitored. In case of fish tanks are operated by only one pump, spare pumps are integrated via two-way connection into my aquaculture system design preventively. If one pump fails for fish tanks operated with 2 pumps the fish tanks can be operated at least with one pump until the spare pump has been installed. In case of minor fish stocks recirculation with only one pump might be enough too. 

High-pressure pumps are utilized for injection of ozone, backwashing of drum filters and transport of well water. 
My partner for pumps is KSB AG.

Piping

 PVC pressure pipes and pressure fittings up to nominal size DN250 are suitable to transport water and air. PVC sewage pipes and sewer fittings are available up to DN500. My partner for PVC piping is LA.RE.TER. Spa.

For water applications of larger nominal diameters I plan pipes made from polyethylene or channels. In Circular Tank Twins© rex-m the effort for piping and ducts is reduced to a minimum. The water recirculation in my large-scale flow-through raceway systems completely dispenses with pipelines and channels.