The introduciton of the Clearwater Bioreactor has been the single most important development in RAS since the early 90`s. For the first time it is now possible to have full biofilm-control.
This basically means that one is operating with a constant fresh biofilm, which does not build up and create diffusion limitations for nutrients going into the biofilm, and metabolic exhausts leaving the film.
Apart from being inherently effective, it also means a very safe and stabil performance.
There are no constant adjustments, no back flushing of biofilters as in fixed bed filters and literally no maintenance.
The CLEARWATER technology is operated with a high rate of aeration, which costs energy, but the net energy consumption for RAS plants is actually less per kg produced fish than other
In favouring nitrifying bacteria and providing optimal conditions for
nitrification, the bio-reactors are constantly operating under nitrogen-limited conditions. This means that a latent capacity exists and has been proven to absorb sudden peak loadings.
In effect, this means that the CLEARWATER bio-reactor is self-adjusting, as the nitrification rate is increased in proportion to the available nutrients.
Energy consumption has always been a key focal point for INTER AQUA Advance and in recent years this issue has gained increased importance.
The advantage of less energy consumption per kg produced fish
is gained through the provision of oxygen and carbon dioxide degassing effect caused by the aeration, which reduces the requirements for subsequent degassing technologies that most often rely on high pumping heads in cascade towers.
Carbon dioxide degassing effects of 50-75% have been demonstrated with the CLEARWATER bio-reactors.
Supply of pure oxygen can similarly be reduced,since the CLEARWATER bio-reactor is designed to operate at 90-95% oxygen saturation.
The combination of very low headloss over the bio-reactor, reduction of pumping head and ventilation for degassing and requirement for pure oxygen addition makes 3rd generation CLEARWATER bioreactor RAS plants the most costeffective per kg produced fish.
Fine Particle Removal Biofilm adsorption in CLEARWATER
bio-reactors gives crystal clear water.
Solids capture in aquaculture is also an important issue for maintaining fish health. A major limitation in aquaculture concerning removal of fine particles stems from the very high operational costs necessary to remove very fine particles.
In many Fixed-Bed technology based RAS plants, a large portion of a
system’s fine particle fraction is generated by these stationary biofilters- either as bacteria, inert cell-walls or by breaking down of larger particles of feed and faecal matter.
This is not the case in the 3rd generation CLEARWATER Moving Bed Technology.
Founded solidly on regular water analyses over a period of nine years in the first 3rd generation RAS plant for salmon smolt, supplied by one of our reference companies, it has been demonstrated that given a sufficiently high hydraulic retention time, the fine particles within the CLEARWATER Bioreactor are captured and metabolized by the biofilm.
Due to adsorption of the particles to the sticky biofilm matrix, the
total suspended solids (TSS) concentration is actually reduced and
the plant has been capable of sustaining crystal clear water with a turbidity of less than 1 NTU even at stocking densities as high as 100 kg/m3.
Effect of Bio-Film control in Salmon Smolt Plant
|Retention Time: App. 10 min/pass||Average Stocking Density: 70 kg/m3|
|NH4 - N: < 0.5 mg/L||NH4 - N: < 0.3 mg/L|
|NO2 - N : < 0.2 mg/L||NO2 - N : < 0.1 mg/L|
|BOD5 : 8 mg/L||BOD5 : 3 mg/L|
|CO2 : < 12 mg/L||CO2 : < 6 mg/L|
|TSS : 5-10 mg/L||TSS : 2 mg/L|
|Turbidity : < 1 NTU||Turbidity : < 1 NTU|