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Ozone in Aquaculture (Fish Farming)
OZ-AIR® Ozonation Systems are widely used in aquaculture for water conditioning that improves the health of marine animals.
Conventional means of solids removal, such as sponge/ perlon floss filters and sand filters address the removal of coarse settleable and filterable solids, but not the removal of fine colloidal solids. Similarly, nitrifying bacteria in bio-filters remove dissolved ammonia and nitrite, but not all dissolved organic wastes. As an aquarium matures, the accumulation of dissolved organic colloidal solids increases. This organic buildup decreases the performance of the nitrifying bacteria that convert nitrite to nitrate, thus causing harming nitrite buildup. The biochemical oxygen demand also rises, so the oxygen levels decrease over time. These shifts in water parameters stress the aquarium inhabitants and may even cause mortality. To reduce the necessity of large water changes, that can change the systems chemical parameters (PH, salinity, alkalinity etc.), there is a very efficient alternative method of breaking down these organic wastes using a strong oxidizing agent Ozone.
Ozonated water is widely employed at aquariums, sea parks and zoos, where it safely removes disease causing microbes or fungus without using harsh and increasingly regulated chemicals that may form harmful byproducts.
Use of ozone in aquaculture water treatment serves the following purposes : -
Removal Of Fine And Colloidal Solids
A fine and colloidal solids consist of particles 1-30 microns (mm) and 0.001 (mm) respectively. The small size of the particles enables the solids to remain in suspension and avoid most mechanical methods of separation. The accumulation of fine and colloidal solids can impair bio-filter nitrification efficiencies and stress fish stocks
Ozone removes fine and colloidal solids by causing clumping of the solids (microflocculation), which facilitates removal by foam-fractionation, filtration and sedimentation.
Removal Of Dissolved Organic Compounds
Dissolved organic compounds or refractory organics, give the water a characteristic tea-colored stain. Dissolved organic compounds are non-biodegradable and accumulate according to feed input, water exchange rate and the rate of solids removal. High levels of Dissolved organic compounds can stress fish and reduce nitrification efficiencies of the bio-filter. Ozone removes dissolved organic compounds by :
Removal Of Nitrite
Nitrite can accumulate as production intensifies and organic loadings increase. Bacteria that process ammonia into nitrite (Nitrosomonas spp) operates more efficiently under high organic loadings than bacteria that process nitrite to nitrate (Nitrobacter) and levels of nitrite rise accordingly. High levels of nitrite can be toxic to fish. Data available for silver perch, bidyanus bidyanus indicates levels of nitrite as low as 2.8 parts per million (ppm) can reduce growth of fingerlings by 5%.
The high stocking densities, associated fish stress and increased nutrient loads found in RAS create an ideal environment for fish pathogens. An important step in reducing the risk of disease outbreaks in RAS is the use of standard quarantine procedures for any fish introduced. Facilities using surface waters, including RAS and flow through hatchery systems, are also interested in reducing the pathogens load introduced via the source of water. The disinfection of effluent waters introduction to the environment is also crucial to prevent the translocation of exotic diseases.
Ozone can effectively inactivate a range of bacterial, viral, fungal and protozoan fish pathogens. The effectiveness of Ozone treatment depends on ozone concentration, length of ozone exposure (contact time), pathogen loads and levels of organic matter. If high levels of organic matter are present, the demand created by oxidizing the organic matter can make it difficult to maintain enough residual ozone for effective disinfection.
Advantages Of Using Ozone In Aquaculture Environment