It is difficult or almost impossible to achieve an effective control of harmful microbes in natural water. The increased consumption of aquatic products by consumers all over the world has led to more and more fish farming in limited environments. This has brought enormous environmental pressure and, at the same time, increasing crisis in habitat water sources at hatcheries and seafood rearing facilities. Today, there is growing concern about the impact of problematic natural water on aquaculture. Taking salmon as an example, many farmed fish can be affected by bacteria, viral and infectious and parasitic fish diseases during the process of growth.
In order to minimize the spread of infectious and parasitic fish diseases between fish in the facilities and wild fish outside, measures need to be taken to sterilize the fish hatchery water and the water that will enter the hatchery in the future. Chemical sterilization is not practical. Not only do chemicals pose a threat to fish, but water treated with chemicals is not allowed to be discharged into natural waters any more. In this case, Ultraviolet (UV) water treatment, as a non-chemical treatment method, can provide a perfect solution in this regard.
How Does UV Light work?
UV light can be divided into UVA (315-400 nm), UVB (280-315 nm) and UVC (100-280 nm) according to its wavelength. Among them, UVC with a wavelength of 254 nm is a radiation frequency with high sterilization effect. When UV light is applied for water treatment, its radiation energy can permanently change the DNA of the microbes present in the water in a process called thymine dimerization. Microbes that have been treated by thymine dimerization will die quickly because they cannot perform their essential functions such as respiration, assimilation of food, and replication.
UV Water Treatment and Aquaculture
The powerful sterilization effect of the UV light is the reason why it is introduced into aquaculture industry. By killing a variety of bacteria, viruses or parasites that are harmful to fish, UV water treatment can significantly reduce the number of pathogens in hatcheries and farming facilities by more than 99%, thereby improving the quality of problematic water sources to be used. UV light has been proven to be the most cost-effective method to kill multiple kinds of bacteria, viruses or parasites harmful to the living of fish. In addition, ozone is often used in fish hatcheries for the improvement of water quality. But in some cases, excessive ozone that has been temporarily left in the water can be dangerous to aquatic lives. UV treatment can notably accelerate the depletion of the ozone existed in the water, which will provide a much healthier water source for fish farming and other aquatic products.
Advantages of UV Water Treatment
Compared with other water treatment methods, UV water treatment has long been proven to be effective and reliable. Multiple advantages in UV treatment make it widely applicable in the sterilization of drinking water, aquaculture water and wastewater treatment as the best solution. The advantages of UV water treatment can be concluded in the following:
- UV sterilization is super-fast. According to experiments, UV sterilization time for Staphylococcus is about 1.23 seconds. The time needed to kill Streptomyces is about 0.4-1.5 seconds. And it takes only 0.15 seconds to kill dysentery bacillus. For coxsackievirus, it only takes UV light 0.08 seconds to kill them. Even for the stubborn tobacco mosaic virus, the time needed is about 1.6 seconds. UV light can finish the sterilization of common fungal spores in less than 1 second. For the stubborn fungi from excreta, which take the longest time, it need only 8 seconds. The sterilization of algae usually takes a longer period of time. UV can kill the blue algae and green algae and blue-green algae in 10-40 seconds. For common pathogenic bacteria in fish farming, they can be eliminated within 10 seconds.
- UV water treatment in aquaculture uses and produces no chemicals in the process. It will not change the composition or chemical properties of the water such as its pH level, taste, smell, or color. Therefore, it will not cause any negative effect on fish when it is used.
- Compared with chemical treatment methods such as chlorination, UV water treatment doesn’t involve the use of any chemicals. As a result, the implementation of UV water treatment for the sterilization of aquaculture water will be easier than the chemical methods. Therefore, it is also more cost-effective.
- By adopting UV water treatment, operators of fish hatcheries or farms can spend more time and attention on fish hatchery rather than on the treatment of aquaculture water.
To get a deeper and comprehensive understanding of both UV light and a UV water treatment, please go to our previous blog: Advantages and Disadvantages of UV Water Treatment. Next, we will take a look at what will affect the performance of UV water treatment.
Influencing Factors in UV Water Treatment
In aquaculture, as in other applications, the effectiveness of UV treatment will be affected by a number of factors. These factors include UV transmittance, turbidity, hardness and chroma of the water, content of heavy metals such as iron and magnesium, content of suspended solids and flow rate of water, etc. Certain factors, such as water turbidity and UV transmittance, will influence each other. Iron and magnesium elements should be removed from the water in the pretreatment phase. The content of iron and manganese in the treated water should not respectively exceed 3 ppm and 0.5 ppm. In addition, since UV radiation decays with distance, the thickness of the water layer also determines the sterilization effect.
There are other factors that also affect the sterilization effect of UV light. First of all, in addition to the physical and chemical properties of the water itself, the sterilization efficacy of UV light is also related to the power of the UV lamps. The greater the power of the lamps are, the stronger the UV radiation will be, as well as the UV sterilization efficacy. Secondly, the thickness and purity of the protective quartz sleeves outside the UV lamps also directly affect the transmittance of UV light. Quartz sleeves with less thickness and higher purity will be better choices. The sterilization efficacy of UV water treatment is also determined by the temperature of water. Experimental data show that the optimal working temperature for a UV water treatment unit with UV lamps inside quartz sleeves is between 70-100 F.
Our Expertise
For years, with the extensive experience in the manufacture and service of UV water treatment equipment, Puritor has been providing the optimal UV water treatment solutions for a wide range of industries. Our equipment provides clean and safe water resource for food and beverage production enterprises, fish hatcheries, aquaculture resource programs, incubation and rehabilitation facilities, etc. Our water treatment solutions have also been providing great convenience for water sterilization in swimming pools, aquariums, wastewater reuse, etc.
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