| With the continuous development of marine economy,the marine ecological environment is deteriorating increasingly,the traditional marine aquaculture model of extensive management and resource dependence can no longer conform to sustainable development in the present age.In order to balance the contradictions between economic development and ecological environmental protection,realize the environment-friendly production,Recirculating Aquaculture System as a controllable environment,green and efficient,aquaculture model emerged as the times require.Nevertheless,in the intensification of aquaculture process,people seek after culture efficiency excessively so that people increase stocking density blindly,disregard the importance of the treatment efficiency of aquaculture wastewater.Unfortunately,not only does constitute a menace to aquaculture animals,but also aquaculture wastewater untreated discharges will pollute the marine ecological environment.Therefore,it has great realistic significance to determine the appropriate stocking density and take effective measures to improve the efficiency of aquaculture wastewater treatment for achieving of circular economy and efficient development of the marine economy.Based on H.discus hannai Ino aquaculture wastewater as the research object,in order to exert the advantages of RAS,enhance equipment efficiency,it requests to compare the characteristics of water environment changes in different stocking densities,analyze the treatment efficiency of biological filter on aquaculture wastewater as to explore the scientific and reasonable breeding density.It also can provide important theoretical and technical basis for the optimization and upgrading of wastewater treatment process as well.With the purpose of understanding the metabolic characteristics of H.discus hannai and the degree of water pollution,it requests to explore the effect of different sizes of abalone metabolites on the water quality.Starting from improving aquaculture environment and the carrying capacity of RAS,the effect of different concentrations of Compound of Bacillus on self-polluted water of H.discus hannai was studied.The main results are as follows,?1?The research was about the optimum stocking density in RAS for multidimensional cultivation.The results about the effect of stocking densities?500 individuals/m2,300 individuals/m2,100 individuals/m2 respectively?on the water environment of RAS demonstrated that the average concentration of water quality index of each density group tended to be stable and showed significant difference over time.The average concentrations of TAN,NO2--N,PO43--P of each density groups differed significantly?p<0.05?.The relationship among these was high density group> medium density group> low density group;The average concentrations of NO3--N and VBC in high and medium density groups were significantly higher than those of the small group?p<0.05?.The high density group was greater than the low density group.However,high and medium density groups were not significantly different?p>0.05?;The average concentrations of TN,TP,COD,HPC in high density group were significantly higher than those of the medium and small group?p<0.05?.Medium and small density groups were not significantly different?p>0.05?,but the medium density group was greater than the low density group.Although high density group had a significant effect on water quality,TAN and NO2--N which had significant toxic effects on aquaculture were stable at a safe concentration range and had no effect on normal growth.From the analysis of economic and ecological benefits,the stocking density of 500 individuals/m2 can be used as the optimum breeding density of the system to improve resource utilization.?2?The research was about the treatment effect of MBBR on the aquaculture wastewater.At the current operating conditions,the average removal rates of TAN,NO2--N,NO3--N,TN,PO43--P,TP,COD of MBBR in RAS were 16.4%,15.81%,2.93%,12.22%,2.91%,6.48%,9.47% respectively.The results showed that TAN and NO2--N could be reduced better,but the efficiency of nitrogen and phosphorus and low COD concentration removal were low.?3?The research was about the metabolic characteristics of H.discus hannai after food intake and its effects on water quality.With the increase of body size,the ammonia excretion rate per unit weight significantly decreased and the ammonia excretion rate of the small-sized group?body length 16.44±2.93mm?was significantly higher than that of the medium?body 50.63±3.08mm?and large size group?length 76.15±4.16mm??p<0.05?.The average ammonia excretion rate of large,medium,small size groups were 12.23?g/gh,20.77?g/gh,38.03?g/gh respectively.The water quality indexes of each size group were increased with time,and the average concentration of TAN,NO2--N,PO43--P,COD in large size group were significantly higher than those of medium and small size groups?p<0.05?.The relationship between them is medium size group > small size group;The differences were not significant except the average of NO2--N.Experimental results showed that NO3--N concentration of different size groups were not significant?p>0.05?.The results can provide a theoretical basis for predicting water quality change at different stages and have a certain reference value for the study of shellfish energy.?4?The research was about the effect of water purification by different concentrations of Compound of Bacillus.Compound of Bacillus can delay TAN,NO2--N,COD growth in various degrees.Removal efficiency of TAN,NO2--N,COD in high concentration group(2×1013cfu/m3)were extremely significant;Removal efficiency of TAN,NO2--N,COD in medium concentration group(2×1012cfu/m3)were significant?p<0.05?;The removal effect of low concentration group(2×1011cfu/m3)were not obvious.In the 16 th day,compared with the control group,TAN,NO2--N and COD were decreased by 45.5%,47.4%,27.54% in high concentration group and its removal effect was the best.Therefore,Compound of Bacillus can effectively reduce the concentration of major pollutants and can be used as an effective way to reduce energy consumption and reduce production cost. |
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