As climate change progresses, the water content of streams is changing rapidly. In this case, the owner of the trout farm was concerned about the erratic flow in the stream that feeds his farm. The biggest problems were mainly in summer, when the stream dried up several times in dry years.
In cooperation with the owner of the farm, we designed a recirculation system based on the so-called “Danish” type RAS. We have modified the system so that large, energy-intensive blowers are not needed to circulate the water.
The recirculation is therefore not provided by a central airlift, as in the classical concept, but by a tubular pump that can pump the required amount of water at low operating costs. The blower, which is also included in the system, is an order of magnitude smaller and only supplies air to the biofilter and the breeding tanks, using small integrated airlifts.
The integrated airlifts are used for both aeration and to direct the flow in the tank. The pump outlet is designed via a spray plate, where further aeration and partial degassing of the recirculated water takes place.
The RAS consists of three 15 000l rearing tanks. Each tank has a bottom and top collection, drainage and discharge pipes. Each tank has controllable inflow from the flow, from the borehole and from the recirculation circuit. The tanks are equipped with a regulated air supply that is routed to an integrated airlift.
The biofilter is designed as a four-chamber biofilter. The first two chambers are a classic MBBR filter, i.e. a floating bed filter. The third chamber is a fixed bed filtration (FBBR), where suspended solids, i.e. faeces and feed residues, are mechanically separated. This chamber has to be periodically desludged. A system blower is used to wash the fixed medium and has sufficient power for this function. The last chamber is used to house the pump. Each chamber has a drained bottom and is equipped with a drainage pipe.
The system can be operated as a recirculation system, semi-recirculation system with a large water exchange or as a classic flow-through system, depending on the amount of water in the flow.
In case of low water level in the stream, water replenishment is provided by a large borehole.
The system has proved its worth and the farm owner plans to extend it to other reservoirs.
Technical parameters
- Breeding tanks: 15 000 l , 3 pcs
- Mechanical filter: fixed bed bioreactor (FBBR), air wash
- Biological filter: floating bed bioreactor (MBBR)
- Recirculation pump: 60,000l/hr, 180W
- Blower : 2200l/min, 2200W
- Airlift: 3 pcs
- System cabinet
- Annual production approx.: 10 000 kg of marketable rainbow trout
- Total volume: approx. 50 000l
- Flow rate: 56,000l/hr + water exchange from the stream according to current possibilities
- Power consumption: 2400W/hr
- Realisation 2024
Video from this realization can be found here:
https://www.facebook.com/61552907402409/videos/761966315757120
