| In recent years,circulating aquaculture has attracted the attention of the majority of aquatic practitioners,and the water treatment system is its core part,and the water purification efficiency largely determines the advantages and disadvantages of the circulating water system.Ammonia nitrogen and nitrous nitrogen that endanger the healthy growth of aquaculture objects mainly come from the excrement and residual bait of aquaculture objects,and effective degradation of ammonia nitrogen and nitrous nitrogen in water is the key point of aquaculture water purification.Different types of filter media have a great influence on the nitrification performance of water treatment system,this experiment uses trickle flow circulating water aquaculture system,the drip filtration system filled by three filter materials(brush,quartz sand,K3 filler)is studied,and the most suitable filter material is selected as the filling material of the trickle filter box by comparing the hanging effect of the three,the degradation effect of ammonia nitrogen and nitrous nitrogen: among them,the mass of biofilm after demembrane removal of the drip filtration system with K3 packing is the largest,which is 45.67 The removal rate of g.m-2,8h ammonia nitrogen(85.62%)was significantly higher than that of brush and quartz sand biological filter(63.47%,73.66%),and the accumulation of nitrous nitrogen was small.K3 packing was used as the filling material of the trickle box to explore the optimal water treatment effect of the most suitable packing under different operating conditions(temperature,flow rate,initial ammonia nitrogen concentration).The results showed that the K3 packing biological filter had a fast film hanging speed and a fast degradation rate of ammonia nitrogen and nitrous nitrogen.At 30 °C,the concentration of ammonia nitrogen can be reduced to close to 0 after 6h of water circulation,and the removal rate of ammonia nitrogen can be as high as 97%;Within a certain flow rate range,the removal efficiency of ammonia nitrogen will increase with the increase of flow rate.Under the pilot conditions,koi was used as the breeding object,and the operation of the trickle-down circulating aquaculture system and the culture effect of koi were analyzed.The results showed that the water quality indicators in the culture system were within the suitable range,and after 120 days of rearing,the average body mass of koi was 350.58±0.18 g,and the average body length was 27.34±0.31 cm.In addition,the structure of the flora in the drip box before,during and after breeding changed greatly,and the dominant phylum in the early stage of culture were Bacteroides,Proteobacteria,and Actinomycetes.The dominant phylum in the middle of breeding were Phylum Chlorobentomycetes,Proteomycetes and Actinomycetes.The dominant phylum in the later stage of breeding were Proteobacteria,Bacteroides,and Flomerium.By comparing the COG database,it was found that the metabolic functions of each bacterial group were similar,and they were all related to amino acid transport and metabolism,inorganic ion transport and metabolism,and carbohydrate transport and metabolism.Combined with db-RDA,it can be seen that the structure of the flora in the early stage of culture is greatly affected by ammonia nitrogen,and the structure of the microflora in the middle stage of culture is greatly affected by nitrite.The experimental results showed that koi could grow healthily in the circulating aquaculture system,and the succession of bacterial community structure was closely related to the change of water quality.The above research results provide some basic data for the water treatment effect and growth characteristics of aquaculture objects of trickle-down circulating aquaculture,in order to serve as a reference for the production of circulating aquaculture. |
PDF Full Text Request