총 잔류산화제(TRO) 제어 기술을 이용한 양식 넙치의 생산성 향상 연구

Abstract

In this study, the fish mortality rate, feeding status, swimming status, etc. were analyzed by applying ozone to seawater to sterilize influent water and improve water quality. In addition, the correlation between Total residual oxidant (TRO) and Oxidation reduction potential (ORP) was confirmed according to the amount of ozone injected for sterilization, the degree of neutralization of TRO was analyzed according to the amount of neutralizer injected, and the mortality of fish was analyzed. In general, ozone is widely applied to the sterilization and removal of pollutants in industrial water treatment industries such as water and sewage. Unlike ozone applied to freshwater, its application in seawater is very different. Ozone has a very short half-life of 5.3 seconds because it reacts rapidly with bromine ions widely distributed in seawater. However, the half-life of TRO produced by reaction with bromide is relatively long, so TRO can accumulate rapidly with residence time. Therefore, when applied to saltwater fish farming, it is important to automatically adjust the TRO value to maintain an acceptable TRO value for the fish, and if it exceeds the allowable value, it will die. Ozone can be applied in a variety of ways to saltwater fish farming. In order to completely inactivate viruses or parasites contained in the influent, the highest CT value among the influent pathogens is selected and the corresponding ozone injection rate is applied to maintain the TRO concentration for inactivation of the pathogens. In this study, the experiment was conducted focusing on the olive flounder, which has the highest production among domestic farmed fish species. In the case of influent sterilization treatment, in order to secure sufficient residence time to consider the CT value for parasite death, it stays for about 3 minutes or more in the ozone reaction tank (Skimmer) and PE tank (reservoir), and sodium thiosulfate is added to neutralize the high TRO. was used. In order to check and control the neutralization of TRO, the ORP value was allowed to flow into the aquaculture tank in the range of 250 to 280mV. In addition, when configured with a closed-loop water treatment such as seawater RAS, a protein skimmer is typically used to remove fish metabolites and dissolved organic matter and particulate matter. When controlling by injecting plasma (ozone) into Protein Skimer, the aggregation effect is excellent and water quality can be effectively improved by removing the organic matter dissolved in the water. However, if the TRO concentration exceeds the allowable range for farmed fish, it puts a great stress on the fish and eventually leads to death. Therefore, the appropriate TRO concentration range of farmed fish was identified, and the fish status and mortality according to exposure to TRO concentration were analyzed. In addition, in order to effectively control the amount of ozone in the low TRO concentration range, it was compared with the ORP value according to the TRO concentration. The ORP value can be maintained proportionally and linearly according to the TRO concentration, so it was analyzed that the method of automatically controlling the ozone injection amount would be sufficient. However, when high-concentration ozone for influent sterilization was injected, the ORP value did not remain proportionally linear at the high TRO concentration, so it was confirmed that a separate ozone injection rate algorithm was needed. As a result of analyzing the TRO tolerance of Oliver flounder in the flow-through method, it was possible to confirm the stability of the fish at 30 ppb or less.