USING ULTRAVIOLET RAYS IN TREATING WATER IN FISH PONDS IS GRADUALLY BECOMING POPULAR IN INDONESIA.

Indonesian shrimp farmers are gradually transitioning to using ultraviolet (UV) treatment methods to replace chemical water treatment methods in shrimp ponds.

After successful application and becoming part of the water disinfection system in shrimp breeding farms in Indonesia, UV technology is now being considered for use in commercial shrimp ponds.

Reasons to consider UV technology include enhanced biosecurity, reduced common shrimp diseases, long-term water management cost reduction, and the application of environmentally friendly practices.

These factors are weighed against the use of conventional chemicals, such as chlorine or hydrogen peroxide (H₂O₂), which are currently used for disinfection in shrimp ponds.

Initial success in Bali

Some Indonesian farmers have started experimenting with UV technology, including Sidiq Bayu Kurniawan, a shrimp farmer in Bali. He has used FisTx Indonesia’s UV technology in his past two shrimp farming cycles. According to him, UV treatment has significantly reduced the presence of bacteria compared to directly sourcing water from the sea.

Furthermore, he mentioned that UV technology provides both spatial and cost efficiency. Previously, a separate pond was necessary for chlorine treatment. However, with UV treatment, Bayu can directly treat the entire water supply using UV light and directly circulate it into the shrimp pond without the need for a separate treatment pond. This method eliminates the long waiting time for water preparation before stocking the shrimp. Additionally, the UV system is integrated with a sand filter that can improve water clarity and maximize the effectiveness of UV treatment.

In terms of cost, Bayu shared that there are significant savings in the long term. Although the initial investment in UV technology is high, he noted that it greatly reduces the expenses for chlorine and H₂O₂. He mentioned that the total cost of using chlorine in his two farming cycles is nearly equal to the initial investment in the UV system.

ATD PT Suri Tani Pemuka, a subsidiary of Japfa Group, is actively exploring the development and implementation of UV technology in shrimp ponds. According to ATD manager Muhammad Fuadi, residual chlorine tends to cause resistance in pathogens and requires higher dosages in subsequent applications.

Fuadi explained, “For responsible aquaculture operations, we see that UV light is an alternative solution to chlorine or other environmental treatment chemicals that may affect the quality or balance of our ecosystem. Meanwhile, UV light does not leave residues.”

Ensuring treatment effectiveness

UV light is a type of electromagnetic radiation with a shorter wavelength than visible light but longer than X-rays. When it comes to disinfection, a specific type of UV light called UVC with a wavelength ranging from 250 to 265 nm is used. UVC is effective in killing pathogens by damaging their DNA structure, preventing their reproduction, and disabling their ability to cause diseases. Importantly, it does not destroy cells, ensuring that harmful substances within the microorganisms remain trapped within the water environment. However, it is important to note that UV disinfection is only a biological method, and other chemicals like chlorine are still necessary in water treatment processes to maximize treatment efficiency.

Ideally, water should be treated with UV light after physical treatment and before introduced into the shrimp pond. The limitation of UV light lies in the specific water quality requirements, primarily the turbidity level to ensure UV light can penetrate through microorganisms. Some companies have developed UV systems suitable for treating water entering ponds, with two main options being open channel systems and closed-loop systems. Both have their own advantages and disadvantages.

The open channel system is designed to work with a self-flowing gradient stream system, which can save costs for both installation and maintenance. In this system, compartments are usually set up to follow the water path from the reservoir or directly from the sea to the fish pond. However, relying solely on gradient alone may not effectively guide the water, leading to sedimentation and inadequate disinfection. Furthermore, an open setup means that the disinfected water flowing into the pond can still come into contact with pathogens.

On the other hand, in a closed system using pipes as treatment chambers, a high-pressure pump will generate high pressure to effectively move water through the UV light chamber. This method avoids issues of pathogen spread or water treatment efficiency. However, high water pressure can affect the durability of the UV light. Additionally, long-term pipe calcification can cause blockage and increased water pressure.

Fuadi explains, “Excessive high pressure can damage the ultraviolet system, especially the protective sheath and UV light. Typically, concerns about this pressure can be addressed by placing the UV system further away from the pump or closer to the fish pond.”

He points out that, in addition to the type of UV system, there are other factors that affect the effectiveness of UV treatment. This includes the dosage used, which relates to the intensity of the UV light and the water retention time, correlating to the target of the pathogens. For example, he says that combating Vibrio parahaemolyticus (the agent causing EMS/AHPND) often requires 70-100 mJ/cm2 for effective treatment, but some farmers prefer to use up to 300 mJ/cm2. In Fuadi’s own farm, he even operates at levels of up to 1000 mJ/cm2 due to the lack of international standards.

“In our analysis, we often encounter different suggested dosages for the same organism in different scientific journals. So, we tend to assume higher dosages, considering physical and chemical properties consistently. Although this decision generally does not pose problems, it can increase the necessary investment,” Fuadi says. “Typically, we use 300-350 mJ/cm2.”

Furthermore, he notes the importance of pretreatment processes, such as maintaining turbidity below 15 Nephelometric Turbidity Units (NTU), total suspended solids (TSS) below 20 mg/L, and chemical oxygen demand (COD) below 20 mg/L.

Long-term effectiveness

Fuadi agrees with the farmers’ perception of the cost-effectiveness of UV treatment. Based on his calculations, using UV light saves costs about 16 times compared to chemical disinfectants.

“Although the initial investment (capital cost) is high, in the long run, it only requires operational costs, such as electricity costs (opex). This operational cost is much cheaper than using 30 ppm chlorine or TCCA (trichloroisocyanuric acid) in each farming batch. The maintenance cost of the UV system is not high, mainly related to the UV sheath or lamp housing, as they tend to degrade over time when in contact with seawater. So, if we compare directly between chlorine or TCCA and UV, to achieve payback, that can be done within three cycles. Around one year, assuming the survival rate is about 80% on average,” he explains.

The cost effectiveness also depends on the dosage, depending on the farmers’ needs. Determining the appropriate dosage and investment value depends on the condition and disease history of the fish pond. The intensity of the UV light is not fixed as it needs to adapt to different locations, affected by different water compositions, past farming methods, previous disease occurrences, and water circulation rates. Therefore, the installation must always be adjusted according to specific needs.

Mental barriers

Sidiq Bayu Kurniawan notes that the use of UV technology generally does not cause significant issues. The main challenge revolves around technical maintenance, especially with parts such as the protective sheath, as fish farmers are not familiar with this new technology.

From the manufacturer’s perspective, the main obstacle is introducing and training farmers or farm managers about this technology. Some pond managers or technicians tend to prefer maintaining the status quo, even when the fish farmer expresses interest in implementing UV light. On the other hand, some farmers have higher expectations for UV light. However, Fuadi always emphasizes that although UV light brings various benefits, it is only a part of the production system. Other factors such as nutrition, seed quality, and biological safety also play equally important roles.

(Source: https://tongcucthuysan.gov.vn/)

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