Talking about the design of industrial circulating water aquaculture pond
In the process of starting the industrial circulating aquaculture, one of the first problems faced is the design of the breeding pond. What kind of aquaculture pond should I use? How big is it? what is the material? How deep is appropriate? This is a question that many friends will ask us. Here, we will sort out and summarize the content of the selection and use of circulating water aquaculture ponds for everyone, hoping to play a certain role in helping everyone start work.
Since the mode of recirculating aquaculture is chosen, it must be based on the two basic points of high density and environmental protection and energy saving. One of the key points of high-density circulating aquaculture is to maximize the utilization of aquaculture space, and the other is the efficiency of water circulation and purification.
How to reasonably plan the design area and breeding density of the breeding pond in a limited space environment, and how to let the waste produced by the breeding animals be discharged from the breeding unit into the water treatment unit as soon as possible? These have strict design requirements on the shape, size and depth of the pond.
Classification of circulating water aquaculture ponds:
Sort by material
At present, the commonly used breeding ponds are divided into PP plastic fish ponds, glass fiber reinforced plastic fish ponds, folding fish ponds and cement fish ponds.
PP fish pond: It is made of polymer materials, which is environmentally friendly, non-toxic, smooth surface, corrosion resistance, aging resistance, high strength, long service life, and can be used with confidence in seawater and fresh water. FRP fish pond: chemical corrosion resistance, acid and alkali resistance, aging resistance. The fish pond is light in weight, flexible and convenient to carry, no rust, easy to assemble, easy to disassemble, glass fiber reinforced material, no harm to the water quality and size of the fry to the breeding personnel. But it cannot withstand heavy blows, and the adhesive glue will fall off after a long time, so few farms use FRP fish ponds.
Folding fish pond: As the name suggests, it can be folded, it is very convenient to transport and use, and the price is cheap, but the disadvantage is that it is difficult to discharge the dirt in the fish pond, and it needs external tools to discharge.
Cement fish pond: It is a kind of fish pond that is used more often. It mostly uses brick-concrete structure. The most important thing in building a cement aquaculture pond is to do a good job of waterproofing. At the same time, the newly built cement fish pond is too alkaline (the cement is alkaline), and it is necessary to adjust the pH before placing fish; and the surface of the cement fish pond is not smooth, which will scratch the surface of the fish, and cracks will occur after the cement fish pond is used for a long time.
According to the shape of the fish pond
It can be divided into circular, square, oval runway, octagonal and so on.
The circular self-cleaning effect is the best, with better sewage collection and discharge effect, less dead zone of water flow, easy to clean, and can quickly and concentratedly discharge solid waste.
The square pool will form dead corners of water flow in the four corners of the fish pond, and these dead corners are easy to accumulate pollution. In the actual construction process, some building materials are not easy to be made into square and rounded corners due to material, processing technology and transportation, such as PP and other polymer plastic materials.
And since small systems such as experimental systems and seedling systems do not have such large requirements on the breeding area, circular ones are the most suitable. In addition, when building a cement aquaculture pond, the octagonal shape is easier to construct and neatly done, and the use effect is not much affected.
Square-cut and round-cut fish ponds take advantage of the characteristics of round and rectangular ponds in terms of space utilization and water flow shape. Therefore, in the actual engineering practice of recirculating aquaculture, fish ponds are generally designed to be square-cut or square-cut. In this way, it can not only increase the area of aquaculture utilization, but also take advantage of the characteristics of secondary flow to quickly concentrate sewage.
Analysis of cost and aesthetics
The cost of PP fish ponds is greater than that of FRP fish ponds, and the cost of concrete fish ponds is the lowest; in terms of aesthetics, PP fish ponds and FRP fish ponds are better than concrete fish ponds.
After talking about the classification of fish ponds, let's talk about how deep the fish pond should be. The depth of the fish pond has a certain relationship with the ratio of the diameter to the depth, the flow rate at the bottom of the pond and the cultured species. For example, fish ponds with square cut corners and round cut corners are mainly used for breeding flounder and flounder fish. The diameter of the fish pond is generally 6~8m, the depth of the pond generally does not exceed 80cm, and the ratio of diameter to depth exceeds 7:1. The species are mainly benthic, and if the water depth is too deep, the utilization rate of the water body will decrease. In addition, the flow rate at the bottom of the pool is generally the best at 6-8cm/s, which can ensure the self-purification efficiency of the bottom of the pool.
Fish pond inlet, drainage and flow rate:
How to enter the water in a round fish pond
At present, there are mainly four types: （1）open single tube,（2） uniform opening horizontal tube, （3）uniform opening vertical tube, and（4）uniform opening horizontal tube plus vertical tube.
The open single pipe will cause uneven distribution of water velocity, poor mixing ability of water body, easy generation of non-swirl zone, short-circuit flow to form dead zone, sediment can not be effectively concentrated in the center of the bottom of the fish pond, resulting in poor sewage discharge capacity, etc. The pipe will cause poor mixing ability and water exchange at the bottom of the fish pond, which is not conducive to centralized sewage discharge; although the vertical pipe with uniform opening can make the water flow state self-cleaning function, if the flow rate is too large, it will lead to the formation of dead zone, which is not conducive to Sewage discharge and water exchange; open evenly distributed horizontal pipes and vertical pipes can make the water flow to achieve uniform mixing, effectively prevent the formation of dead zones, and have a good cleaning effect.
Drainage of aquaculture ponds
The drainage methods of aquaculture ponds are mainly divided into single row and double row. The single row is to set a drain in the center of the bottom of the pond, and the dirt is taken out of the fish pond with the water flow. The structure is simple and the function is single.
The double drainage system divides the water out of the fish pond into two channels. The total particle content of one channel of the futures is higher and the flow rate is smaller, which is called the bottom drain; the other channel with better water quality and higher flow rate is called the upper drain (or side drain). This kind of design helps to realize the grading treatment of aquaculture sewage, reduce the water treatment load, and improve the water treatment effect. The feed used in domestic flounder and flounder fish farming has high oil content, and the drainage of the breeding pond will be designed as a bottom row combined with surface overflow.
Flow rate
From the point of view of maintaining fish health, in order to enable the particles to be discharged from the fish pond quickly and in time, the flow rate in the pond should be controlled at 15~30cm/s. Of course, the required design flow rate will be different depending on the variety of cultured species. This needs to be based on The specific situation selects the corresponding style and specifications of the breeding pond.
