Effect Of Activated Carbon On Biological Floc Aquaculture System

As a new aquaculture technology,biological floc technology can convert nitrogen-containing pollutants in water into organic nitrogen,and combine organic particles to form biological flocs that can be eaten by fish.Biological flocculation technology is widely used in aquaculture.However,In the process of aquaculture,the biological floc technology has the problems of long culture cycle,unstable water treatment effect,massive growth of assimilating bacteria,resulting in competition for oxygen with fish and so on.In this study,the activated carbon technology（PACT）was applied to the aquaculture process,and its role in the aquaculture system was studied by adding powdered activated carbon（PAC）to the biological flocs.1.Study on the morphology,particle size and water treatment effect of activated carbon on biological flocsIn order to explore the biological floc culture process,experiments were carried out on the particle size,morphology and water treatment effect of activated carbon in the biological floc culture process.The pilot scale microbial suspension growth reactor is used as floc culture equipment,and the tilapia is cultured on the runway to provide fish culture water circulation.The breeding cycle is 41 days.During the period;the water quality index and floc index of the breeding system were measured.After the experiment,the degradation of nitrogen-containing pollutants was continuously monitored,and the two floc microorganisms were sampled and analyzed.The results showed that the particle size of ordinary floc and activated carbon floc increased continuously during the culture process,and the particle size of ordinary floc was larger than that of activated carbon floc,and both reached the maximum at the end of the experiment;During the period of biological floc culture,the reactors of ordinary group and activated carbon group have stable removal effects on TAN and NO₂^--N,and the concentrations of TAN and NO₂^--N are at a very low level and remain stable.During the whole experiment,NO₃^--N in the inlet and outlet water of the reactor of ordinary group and activated carbon group fluctuated up and down between 0-2mg/L.A small amount of floc in the sedimentation area of the reactor entered the runway of the breeding area during the water change process,resulting in nitrification in the breeding area in the middle and later stage of the experiment.TAN and NO₂^--N decreased rapidly in the middle and later stage of the experiment,and NO₃^--N gradually increased to 5mg/L.In the process of continuous monitoring of nitrogen-containing pollutants,both groups of flocs have good treatment effect on TAN,and can remove 8.5 mg/L TAN within 2.5h.The removal rate of TAN in the ordinary group is 3.13 mg/L·h,and that in the activated carbon group is 3.12 mg/L·h,which is similar.2.Effects of activated carbon on water quality and nitrification function of tilapia during cultureIn this experiment,powdered activated carbon was added to the biological flocs to study the water quality treatment effect of ordinary biological flocs and biological flocs added with activated carbon in the process of tilapia breeding,and the nitrification ability of the two flocs after breeding,in order to provide reference for the working conditions of biological floc breeding.From the whole breeding cycle,the Tan of the two groups fluctuated to a certain extent,but always maintained at a low level.Compared with ordinary flocs,the fluctuation of activated carbon flocs was greater;Activated carbon floc NO₂^--N fluctuated two weeks before the experiment,and then remained at a very low level;The concentrations of NO₃^--N and PO₄^2--P in the two groups accumulated with the increase of breeding time,and reached the highest value at the end of the experiment.Compared with ordinary flocs,the NO₃^--N and PO₄^2--P water of activated carbon flocs are lower than ordinary flocs on average.Activated carbon flocs can not only remove Tan and NO₂^--N in the process of aquaculture,but also help to reduce the accumulation of nitrogen and phosphorus.3.Effects of activated carbon on the nutrient composition of biological flocs and the growth of tilapiaIn this experiment,powdered activated carbon was added to the biological flocs to study the differences of different flocs’nutritional components and the growth and nutritional value of tilapia after breeding.The purpose is to provide reference for the working conditions of biological floc culture.After 56 days of culture cycle,tilapia in GA and GB groups grew well,and the specific growth rate was more than 2.0.Compared with GA group activated carbon flocs,the weight gain rate and specific growth rate of tilapia cultured in GB group were higher.The crude protein,crude fat,crude ash,amino acids and fatty acids of the two groups were determined.The crude protein content of the two groups was about 25%and the crude fat content was between 1%～1.5%.The crude protein and crude fat of activated carbon flocs were higher than that of ordinary flocs,but the difference was not significant.The crude ash content of activated carbon flocs was significantly lower than that of ordinary flocs,The amino acid content of activated carbon flocs is generally higher than that of ordinary flocs.From the amino acid score results,the AAS,CS and EAAI of activated carbon flocs are higher than that of ordinary flocs,indicating that the nutritional value of activated carbon biological flocs is higher.The crude protein content of tilapia muscle cultured with activated carbon flocs was significantly higher than that of ordinary flocs,and the crude fat content was significantly lower than that of ordinary flocs.Under the two breeding backgrounds,the total amino acid content of tilapia muscle was similar,but the content of essential amino acid in activated carbon group was significantly higher than that in normal group.