As a new aquaculture model, industrial recirculating aquaculture creates a living environment suitable for aquaculture organisms through scientific management, so as to get rid of the restrictions of climate, land, water and other external conditions. The aquaculture pond is the growth space of the whole life cycle of aquaculture organisms, and it is also the key infrastructure of the circulating aquaculture system.
Today we will introduce aquaculture ponds.
Aquaculture ponds are mainly divided into the following categories according to their shape: round pool, rectangular pool, octagonal pool, arc pool...
What kind of pond is the ideal "house" for industrial aquaculture? Here we need to consider, as a high-density recirculating aquaculture, what are the two key elements of the aquaculture tank?
1. Maximize space utilization; 2. Pollution collection effect of breeding ponds
To maximize the space, we can raise more fish in the unit space, have more output, and achieve the goal of water saving, land saving and high yield.
The pollution collection efficiency is good enough to discharge the waste metabolized by the fish fish into the filtration system as soon as possible. Only when the waste is treated in time can the recycling of aquaculture water be realized.
Liaoning Academy of Marine and Fishery Sciences also conducted experiments to compare the collection efficiency of the second element: based on the common aquaculture pond forms such as square pond, octagon pond and circular pond, the collection capacity of different pond types under the same inflow flow was analyzed by analyzing the flow cloud map and vector diagram in the aquaculture pond, and the energy consumption under the same pollution collection effect was compared.
Set the water flow rate to 0.5 cycles/hour, and the initial speed of the water inlet to 0.2m/s. The water flow velocity in octagonal pool is 0.07m/s, while that in circular pool is 0.12m/s. There are more small vortices in the flow field and the direction is disordered, and there are fewer small vortices in the circular pool. Compared with the water velocity in the pool, the pollution collecting capacity of the Octagonal pool is 41% lower than that of the circular pool.
When the flow rate of the octagon pool is 0.5 cycles/hour, the flow rate of the inlet at this time is 0.2m/s. When the flow rate of the circular pool is 0.13m/s, the distribution of the velocity cloud image of the internal flow field is similar to that of the octagon. By observing the flow distribution of the circular pool and the octagon pool, under the condition of similar sewage collection effect, the circular pool is compared with the octagon pool. It can save about 35% of the inlet flow rate.
Through the experimental data, we can summarize:
1
Square aquaculture tank
The space utilization rate is relatively high. Restricted by the geometry of the pool wall, the water flow will turn sharply at right angles and impact with the pool wall, resulting in a large energy loss. The remaining energy in the pool is difficult to maintain the rotational motion of the water body at a high speed, resulting in the increase of the low-velocity area in the pool. In addition, the poor hydraulic mixing conditions lead to the generation of "dead zone", the solid waste is difficult to remove in time, and the oxygen consumption in the pool is increased, which leads to the uneven distribution of fish and the decline of fish quality.
2
Star anise breeding pond
Octagon ponds and rectangular arc corner ponds are the best alternatives to circular ponds, with better space management, shared side walkways, and uniform rotating fluid units. However, there is still a considerable difference in the flow rate and water quality in the tank. For example, dead water areas may form near the corners of octagonal breeding ponds.
3
Circular aquaculture tank
Circular, is the mainstream "house type" in the current circulating water aquaculture tank, uniform water quality and stable flow mode, providing relatively better hydrodynamic conditions for aquaculture fish, the higher flow rate in the tank makes the solid waste quickly moved out of the aquaculture tank to achieve self-cleaning;
Although the space utilization rate is lower than that of the square pool, in factory farming, the circular pool with more uniform dissolved oxygen distribution, more stable water flow pattern, and superior water collection effect is the "high distribution" aquaculture tank household standard!
