Disinfection Techniques for Aquaculture Water

Disinfection Techniques for Aquaculture Water

Disinfection techniques for aquaculture water typically include several methods such as ultraviolet (UV) sterilization, ozone disinfection, and chemical disinfection. Today, we will introduce UV and ozone as two methods for sterilization and disinfection. This article primarily analyzes these methods from the perspectives of sterilization mechanisms and characteristics.

UV Sterilization

The principle of UV sterilization involves the absorption of UV light energy by microbial nucleic acids, including ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). This absorption alters their biological activity, leading to the breakage of nucleic acid bonds and chains, cross-linking within the nucleic acids, and the formation of photoproducts, thereby preventing microbial replication and causing lethal damage. UV light is categorized into UVA (315~400nm), UVB (280~315nm), UVC (200~280nm), and vacuum UV (100~200nm). Among these, UVA and UVB are capable of reaching the Earth's surface through the ozone layer and cloud cover. UVC, known as UV-C disinfection technology, exhibits the strongest sterilization effect.

The effectiveness of UV sterilization depends on the dose of UV radiation received by the microorganisms, as well as factors such as UV output energy, lamp type, light intensity, and duration of use. UV irradiation dose refers to the amount of specific wavelength UV required to achieve a certain bacteria inactivation rate. Higher doses result in higher disinfection efficiency. UV sterilization is advantageous due to its strong bactericidal power, rapid action, lack of chemical additives, absence of toxic by-products, and ease of operation. UV sterilizers typically use stainless steel as the main material, with high-purity quartz tubes and high-performance quartz UV lamps, ensuring long life and reliable performance. Imported lamps can have a lifespan of up to 9000 hours.

Ozone Disinfection

Ozone is a potent oxidant, and its sterilization process involves biochemical oxidation reactions. Ozone sterilization operates through three forms: (1) oxidizing and decomposing enzymes within bacteria that utilize glucose, thereby deactivating bacteria; (2) directly interacting with bacteria and viruses, disrupting microbial metabolism and causing death; and (3) entering cells through cell membranes, acting on outer membrane lipoproteins and internal lipopolysaccharides, leading to bacterial dissolution and death. Ozone sterilization is broad-spectrum and lytic, effectively eliminating bacteria, spores, viruses, fungi, and can even destroy botulinum toxin. Additionally, ozone quickly decomposes into oxygen or single oxygen atoms due to its poor stability. Single oxygen atoms can recombine to form oxygen molecules, enhancing aquaculture water oxygenation without leaving any toxic residues. Thus, ozone is considered an ideal, non-polluting disinfectant.

While ozone has effective sterilization capabilities, excessive use can harm aquaculture animals. Studies by Schroeder et al. demonstrate that ozone, when used appropriately, can effectively remove nitrate and yellow impurities, and when used with foam separation, can reduce bacterial proliferation. However, overuse can generate highly toxic oxidants. Silva et al. also highlight that while ozone improves water quality stability and disease suppression in aquaculture, its genotoxic effects can damage cell integrity in aquatic organisms, leading to health issues and reduced yield. Therefore, it is crucial in aquaculture to use ozone in a timely, measured, safe, and regulated manner, implementing strict measures to prevent excessive use and mitigate ozone spillage to avoid air pollution.