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How to supply high density oxygen to aquaculture ponds?

1. Introduction

The air supply in aquaculture is an important issue for the development of the industry. Pure oxygen oxygenation technology has widely been used in air supply for air supplying to seafood. However, oxygenation efficiency is no longer very high and low-density pure oxygen technology is widely applied. Pure oxygen technology employs a proper design of catalyst, has a lower consumption rate and shorter reaction time, and has long-term stability than other technologies. Pure oxygen technology also has advantages in that higher efficiency can be achieved without loss of quality, and it can also avoid breathability problems, especially at high temperatures.
This paper introduces a new pure oxygen technology that utilizes a reverse osmosis water membrane as the separation media (ROD) to improve pure oxygen gas permeability to enhance gas permeability through the membrane surface area. The performance of this new pure oxygen technology was evaluated by using samples from four different species (fish, shrimp, and mussels) treated with different types of ROD membranes. Three kinds of ROD membranes were used: an ionic type ROD membrane (I-ROD), a pore-type ROD membrane (P-ROD), and an extended type ROD membrane (EXT). The solid density difference between different types of ROD membranes was small; however, there was a strong tendency toward lower liquid densities compared with conventional methods. A large difference in liquid densities between the two kinds of P-ROD membranes was observed due to their different fluidity design characteristics; however, this difference could be resolved by adjusting the fluidity characteristics of P-RODs by adjusting their porosities or porosity ratios during the manufacturing process; therefore, this study shows that there is no need for further improvements on this parameter since it can be easily adjusted by changing these parameters alone without affecting other properties such as density difference or flow resistance.

2. What is pure oxygen oxygenation?

Pure oxygen has advantages in technology and economy, but it is not always an effective method for reversing hypoxia in fish ponds. On the other hand, if pure oxygen is used together with a physiological corrective solution, it can be used to control the hypoxia that occurs in aquaculture ponds.
One of the most important challenges in aquaculture is controlling the concentration of oxygen in fish pond water. Oxygen levels should not exceed 5 mg/l (mg/l = milliliter). A critical level is reached when a pH value reaches 7.2 or an alkalinity value exceeds 1.2 gm/l (mg/l = milliliter).
There are many methods to supply high density oxygen to aquaculture ponds, but traditional air oxygenation methods do not meet the needs of fish pond owners because their cost per kg is high and their operational cost is high due to high air exposure during maintenance and operation activities.

3. The advantages of pure oxygen oxygenation

Pure oxygen oxygenation technology is the most popular way to supply high-density oxygen (HDO) to aquaculture ponds. It consists of two systems: an air-pressure portable cylinder and a liquid-pressure portable cylinder.
The portable cylinder consists of a cylinder, a pressure gauge, and a hose. The hose has an outlet on the lower part of its hose that may be attached to one of the ports for supplying pure oxygen gas. The pressure gauge is used to determine the amount of pure oxygen gas that is supplied when the air pressure inside the cylinder is released.
The liquid-pressure portable cylinder comes with three main components: an air-pressure pump, an oxygen sensor, and a membrane valve. The air-pressure pump may be used to supply pure oxygen gas into one or more ports in LCV (liquid container volume). When pure oxygen gas is supplied into one or more ports in LCV, it flows through the membrane valve (without mixing with other gases), which causes pure oxygen gas to enter inlet ports and output at outlet ports via filtered water.
Pure oxygen must not be mixed with other gases since it has special properties such as its properties as an oxidant and a reducing agent. Pure oxygen can also be used as a purifier when it is introduced into water still containing natural organic matter such as decaying fish or algae. It can also be used to neutralize toxic substances in aquarium water (it does not have any harmful effects on natural organics).

4. Conclusion

In recent years, there have been many oxygenation technologies that were developed and commercialized. These technologies can be divided into two groups: liquid oxygenation technology and gas oxygenation technology.
Liquid oxygenation technology was developed by the gas industry, but it has not been applied in a wide range of applications because of the high cost and limited efficiency of this type of technology. Liquid oxygen is a gas consisting of nitrogen and oxygen mixed together, which is supplied to aquaculture ponds through a pipeline.
The main disadvantage of this method is that the hydrogen content in pure water must be reduced to less than 0.01%. The resulting product has no purity, which may cause infection problems or growth retardation in fish. The hydrogen concentration in the liquid mixture should be less than 5% or less than 1% depending on the application.
Gas oxygenation technology was developed by the conventional chemical industry, but it has not been applied in a wide variety of applications because of its high cost and limited efficiency. The gas consists mainly of carbon monoxide and nitrogen mixed together, which is supplied to aquaculture ponds via gas lines.
The main advantage of this method is that there are no problems caused by water treatment or purification procedures as well as no risk from contamination with other gases such as methane and ammonia; thus, it is suitable for all kinds of applications.
With pure water supply conditions, both methods are suitable for aquaculture ponds having pure water supplies at room temperature; however, the adoption rate due to environmental reasons may be higher among those with low-temperature supplies (mainly warm-water ponds) at room temperature when compared with those with low-temperature supplies (cool-water ponds).

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