Establishment Of Recirculating Aquaculture System Of Sea Cucumber And Analysis Of Bacterial Diversity In Biological Aerated Filter

There are many problems in the traditional aquaculture of sea cucumber, such aslow survival rate, excessive consumption of the water resources and the energy, seriouswater pollution and aestivation. The recirculating aquaculture and intensive cultivationmode were used in this research. Biological aerated filter （BAF） with high nitrogenremoval efficiency was used as water processing unit to deal with sea cucumberaquaculture wastewater. The removal mechanisms of wastewater pollutant in theaquaculture were studied through microbial diversity in biological aerated filter. Wefound a feasible recirculating aquaculture system of sea cucumber, which could be atheoretical basis for the sustainable development of aquaculture.First, BAF was start-up using the natural circulation biological film formingmethod. Starting conditions were as follows: temperature at23-25℃, pH at7.5-8.0,salinity at25-30‰, COD at the concentration of20mg/L.d, ammonia nitrogen at theconcentration of5mg/L.d, C: N ratio of4, hydraulic retention time of5h. BAF wasstart up successfully at the23rd day. The optimal running conditions were obtainedthrough different influencing factors experiments. The optimal conditions werehydraulic retention time of0.5h, C: N ratio of12, the concentration of dissolvedoxygen of1mg/L. Under this optimal condition, the removal rate of ammonia nitrogenwas99.29%, the removal rate of COD_Mnwas95.63%in the BAF.Second, recirculating aquaculture system of sea cucumber was designed andassembled. There were three units in the aquaculture system, such as water treatmentunit, cultivation unit and automatic control unit. The BAF was a water treatment unit.The recirculating aquaculture system had been run continuously for39days. The resultswere as follows: no disease, good growth, the average growth rate is0.18%. Theconcentration of ammonia nitrogen in sea cucumber aquaculture pond remained0.0300mg/L, the concentration of nitrite nitrogen was about0.0400mg/L, the highestconcentration of nitrate nitrogen up to9.9027mg/L and the highest concentration ofCOD_Mnwas6.2800mg/L. They all met the requirements of sea cucumber aquaculture.The concentrations of ammonia nitrogen, nitrite nitrogen, nitrate nitrogen and COD_Mnof inlet and effluent in the biological aerated filter were all below the safety concentration.Third, biomass, biological activity and bacterial diversity on the oyster shell carrierin BAF were measured.. The results showed that both the biomass on the oyster shellcarrier and the biological activity of biofilm were all decreased gradually from bottomto top. There were8phylums of bacteria in BAF, including Proteobacteria,Actinobacteria, Bacteroidetes, Nitrospirae, Planctomycetes, Firmicutes,Deferribacteraceae and Yerrucomicrobia. The dominant bacteria group （accountedingfor72.4%） was Proteobacteria, which were mainly responsible for the decomposition ofpollutants in sea cucumber aquaculture wastewater. Nitrospira was the main bacteria fornitrification reaction in BAF. Burkholderiales and rhizobiales were the main bacteria fordenitrification.