Study On Nitrogen Removal From Aquaculture Water By Immobilized Microorganisms

With the development of aquaculture to a high density and intensification model,the problem of nitrogen pollution in aquaculture water has caused widespread concern in society.Nitrogen pollution can harm the health of farmed animals and affect the sustainable development of aquaculture.In this study,three strains of AD012(Pseudomonas otitidis),LAB004(Bacillus subtilis)and NSP001(Pseudom onas nitroreducens)with better nitrogen removal performance were screened from the cultured fish pond water.Antagonistic experiments on three strains showed that the antagonistic effect was negative.The three strains were compounded,and the nitrogen removal ability of the single strain and the combined bacteria was analyzed.The results showed that the combined bacteria composed of the three strains had better denitrification effect.The optimum proportion of the combined bacteria was ADO 12:LAB004:NSP101=0.571:0.791:0.9]0 through the mixture design and the environmental conditions of the composite flora were further optimized.The optimal nitrogen removal environment for the initial inoculum was 8%,C/N=15:1 and pH=8.under this condition,the removal rates of NH3-N,NO2-N and NO3-N reached 95.21%,100.00%and 99.72%,respectively,and four different carbon sources were selected for analysis the effect of carbon source on the growth and denitrification performance of the composite flora showed that the composite flora grew well and the denitrification rate was higher when sodium acetate was used as the carbon source.The composite flora was embedded and immobilized with sodium alginate and polyvinyl alcohol as immobilized materials.When the embedding conditions were 8%PVA,5%SA and 3%Cacl2,the stability of the immobilized pellets,sphericity and mass transfer performance are better.When the immobilized pellets have the bacteria quantity of 20%,dosage 0.5g/L,temperature 30? and pH=S.the nitrogen removal effect is the most and the removal rates of NH3-N,NO2-N and NO3-N were 94.52%,98.93%and 99.31%,respectively.After 12 days of adding immobilization of the composite microbial pellets in the indoor simulation experiment,the removal rates of NO2-N and NO3-N were higher,both of which reached more than 90%,and the removal rate of NH3-N reached 88.46%.The immobilized composite microbial pellet has good denitrification effect and has good application potential in the treatment of nitrogen pollution in aquaculture water.