Study On Purification Effect Of Aquaculture Tailwater By The Bacteria-algae-shellfish System

In order to solve the problem of aquaculture tailwater qualified discharge,this paper studies the effect of purification and growth in aquaculture tailwater by studying the single factor and mixed treatment of 4 kinds of bait microalgae and 2 kinds of probiotic bacteria.In addition,Ruditapes philippinarum were used as the research object to study the effect of mixed bait and algae diets by evaluating the growth of young shellfish and the changes of water quality during breeding.It is hoped to provide a theoretical reference for exploring the resource utilization mode of aquaculture tailwater.Firstly,this article describes the research background of the subject,and introduces the current status of aquaculture pollution,the mechanism of pollution of aquatic organisms by pollutants,the evolution process of aquaculture wastewater treatment methods,and the research progress of bivalve mollusk’s diet.Secondly,the research on the water purification effect of bacteria and algae was carried out in this article by single algae,single bacteria effect and mixed bacteria-algae effect.The results are as follows:（1）Four common bait microalgae,including Chaetoceros muelleri,Platymonas helgolandica,Pavlova viridis,and Chlorella vulgaris,was studied for its purification effect,and it was found that Pavlova viridis had the best removal effect of NH₄⁺-N and NO₂^--N,with the highest removal efficiency of 88.35%and 97.43%respectively.Chlorella vulgaris removal rate was the highest at93.29%about PO₄^3--P.In terms of growth,the relative growth rate of Pavlova viridis was the highest.（2）Two probiotics that is the photosynthetic bacteria and marine red yeast with higher nutritional value were selected.After analyzing the water purification capacity of the two strains,it was found that the PSB had better growth effect in simulated aquaculture tailwater,and had higher removal rates of NH₄⁺-N and PO₄^3--P,and the highest removal rate were 64.57%and 79.27%,respectively.MRY showed high removal rate of NO₂^--N,which was 54.07%.（3）The experiment selected Pavlova viridis,PSB and MRY,and studied the purification effect and growth of different mixed algae-bacteria treatment in simulated tailwater.The results showed that the water purification effect was not ideal in the treatment with a high proportion of bacteria addition,and the water purification effect of the PSB and algal system was better than that of the marine red yeast system.In the PSB and microalgae treatment group,the 5%PSB addition group had the best effect on NH₄⁺-N removal,with a highest removal rate of 89.14%,and the 20%PSB treatment group had the best removal effect on NO₂^--N,with a highest of 93.33%.The difference of PO₄^3--P removal was not significant in all experimental groups.In the marine red yeast and microalgae treatment group,the water purification effect of the microalgae group was generally better than that of the mixed treatment group.In addition,the 5%yeast addition group had the highest removal rates on NH₄⁺-N、NO₂^--N and PO₄^3--P,with highest removal rates of 83.97%,83.52%,and90.43%,respectively.Finally,the effect of bacterial and algae bait was studied.In the experiment,Ruditapes philippinarum young shellfish were used as the research object,and the effects of bacterial and algae bait after mixing with different proportions were investigated.The results showed that the growth rate of juveniles in the 5%PSB addition group was the best,and it’s relative growth rate is 109.55%higher than that of the microalgae group and other groups,Based on the water quality indicators,the 5%PSB added group’s effect is most obvious.Among the MRY and microalgae group,the juveniles grows best in the 40%MRY added group and the specific growth rate is 64.15%higher than the microalgae group,followed by the 70%and 10%MRY added groups.However the nitrogen and phosphorus concentration of the high percentage added group is higher than the microalgae group.Therefore,the bait effect,nitrogen and phosphorus concentration control of the 40%MRY added group are the best.