Study On The Application Of Ozone In The Treatment Of Water For The Culture Of Penaeus Vannamei In Biofloc

The use of biofloc technology to carry out the intermediate cultivation of Penaeus vannamei larvae can effectively remove ammonia nitrogen and nitrite from the tail water to stabilize the water quality and improve the water utilization rate.However,in the late stage of biofloc intermediate cultivation,there are phenomena such as high concentration of organic pollutants,high number of Vibrio per unit of water,and high consumption of dissolved oxygen.Unstable water quality and high concentration of organic pollutants make shrimp larvae often in a susceptible state,and their immunity to Vibrio is reduced,causing large-scale seedling drop.In order to reduce the pathogenic bacteria,ammonia nitrogen,solid suspended solids and other factors that are not conducive to the growth and life of Penaeus vannamei in the water environment,this paper uses ozone to study the water quality treatment effect,the change in the number of vibrio and the nitrification activity in the biological floc system.The aim is to provide a basis for improving the water environment and reuse of the biological floc system.The main findings are as follows:1.Effects of ozone treatment time length on the water purification effect in biofloc nursing of Penaeus vannameiBy adding ozone for different periods of time to the biofloc system,the water purification effect and the biochemical impact of the biological flocculation system are discussed,which provides a reference for the water quality control and reuse of the biological flocculation system.The results showed that:（1）The ammonia nitrogen removal effect was as follows:G10（0.14±0.02）>G20（0.16±0.14）>G2.5（0.29±0.02）>G5（0.42±0.1）,the G10 group reduced the ammonia nitrogen by 21.43%relative to the G0 group.（2）Adding ozone has a significant effect on UV₂₅₄and NO₂^--N treatment（P<0.05）,and it shows a downward trend as the ozone treatment time increases.（3）During the experimental reaction process,the DOC in the water of the experimental group（G2.5,G5,G10 and G20）was lower than that of the control group（G0）.At the end of the experiment,the removal of the G20 group increased by10.28%.（4）Ozone has a significant effect on the biodegradability of biofloc breeding tail water,which is beneficial to the later biodegradation and ozone oxidation.The DOC/UV₂₅₄of the G10 group increased by 18.84%compared with the control group.In summary,the ozone dosing time of 10 min has a significant effect on the biological floc aquaculture water.2.Influence of different ozone flow rates on water purification and activity of nitrifying biofloc systemIn order to explore the effect of ozone flow on the evolution of system water quality and the biological activity of bioflocs in a nitrifying biofloc system.Under the condition that the ozone treatment time is 10min,the experiment set 5 groups of different ozone air intake.The ozone air intake is 0.0L/min group as the control group,denoted as the CY0 group.The remaining groups are CY0.1（0.1L/min）,CY0.2（0.2L/min）,CY0.4（0.4L/min）and CY0.8（0.8L/min）.After the ozone dosing is finished,add 2.0m L NH4Cl solution and shake to sample.The samples are taken every 15 minutes for the first 1 hour,and the water quality index changes of the water body are continuously monitored for 6 hours.The experimental results show that compared with the control group（CY0）,adding ozone can effectively increase the dissolved oxygen content of the breeding water body and increase the p H of the water body.The dissolved oxygen and p H of the CY0.8 group increased by 307.09%and3.71%respectively;The effect of ozone oxidation on NO₂^--N was obvious.When the ozone flow rate reached 0.2L/min,the removal rate of NO₂^--N It reaches 100%.The change of NO₃^--N increases first and then decreases with the increase of ozone flow.The concentration of NO₃^--N in CY0.2 group is（66.88±2.34）mg/l;different flow ozone has the effect of removing TSS,UV₂₅₄and Vibrio in water Obviously,it decreases as the flow rate increases.When the flow rate is 0.8L/min,the removal rates of TSS,UV254 and Vibrio in water compared to the control group（CY0）are 31.33%,35.81%,and 100%,respectively.After additional ammonium chloride was added,CY0 and CY0.1 showed a removal effect on TAN.As the reaction time increased,the TAN concentration gradually decreased,but the TAN concentration of CY0.2,CY0.4,and CY0.8 groups increased instead.Therefore,compared with a single biological floc system,adding 0.1L/min ozone can effectively decompose organic matter in the water,increase dissolved oxygen,eliminate Vibrio,etc.,and maintain the biological activity of microorganisms.3.Study on the application of ozone in the intermediate cultivation of the biofloc of Penaeus vannameiIn order to further explore the aquaculture effect of the crude tail water of biofloc after being treated by ozone,the experiment was conducted under the best conditions of ozone dosing with Penaeus vannamei as the cultivating object,and the effect of ozone dosing on the biofloc system was studied.The effects of water purification,vibrio control,and nitrification activity have the following results:（1）Within 5 days of the experiment,the ammonia nitrogen of the experimental group was lower than the control group<1 mg/L;nitrite was also maintained below 2mg/L,and the accumulation of nitrate nitrogen was also suppressed to a certain extent.（2）In the 5 days of experimental cultivate,the cultivate system without ozone treatment was in the aquaculture system.After 2 days of breeding,the TSS increased by 54.55%,and the aquaculture water UV254 reached 0.171 cm-1.The biofloc system TSS treated with ozone was maintained at a low content of<60 mg/L.At the end of the experiment,UV254 was reduced by 15.45%compared with the control group.At the end of the experiment,the total number of Vibrio in the experimental group decreased by 43.30%,and the total number of Vibrio in shrimp decreased by30.23%.（3）The survival rate of shrimp larvae in the experimental group was higher than that in the control group,with a survival rate of 80.67%.Their body length and weight gain were only 1.23%and 1.0%different from those of the control group.It further shows that the low concentration of ammonia nitrogen,nitrite and the reduction of the number of vibrio in water are beneficial to the survival of shrimp larvae.In addition,the size of shrimp larvae in the experimental group is relatively balanced,which is conducive to the management of animal protection and bait feeding in the later period,and reduces the phenomenon of shrimp larvae dropping.In summary,the use of ozone to treat and recycle the standard crude tail water still has a good breeding effect.