Study On Resource Utilization Of Tailwater Solid Waste From Shrimp Culture In Recirculting Aquaculture System

With the development of aquaculture tailwater treatment technology,the separation and treatment of aquaculture solid waste have become one of the most concerning links in tailwater treatment.Aquaculture solid waste has a large quantity,single pollution source,and negative impact on the ecosystem after entering the environment.At present,most studies focus on solid-liquid separation and its effects.Therefore,the harmless and resource utilization of aquaculture solid waste has attracted more and more attention.This study is divided into two parts.The first part mainly studies the natural dissolution of solid waste and the effects of ozone on the water quality parameters and bacterial parameters of aquaculture tailwater.The best optimal solid-liquid separation time and ozone treatment time of aquaculture tail water were investigated.The second part mainly carries on the solid waste feed-utilization experiment and the Nereis diversicolor（N.diversicolor）and Artemia culture experiment.Here,three probiotics,including yeast,lactobacillus,and Effective Microorganisms（EM）,and three supplementary materials,including corn flour,wheat bran,and soybean meal were studied for their effects on solid waste fermented.Several kinds of fermented feeds were produced by probiotic fermentation.Here,two probiotics,including yeast and lactobacillus,and three supplementary materials,including corn flour,glucose,and trace elements were studied for their effects on solid waste fermented.Several kinds of fermentation liquids were produced by probiotic fermentation.The effects of fermented feeds and fermentation liquids on N.diversicolor and Artemia basic indexes,and were studied through culture experiments.The main results of the study are as follows:（1）The results of solid waste dissolution and ozone test showed that with the dissolution of solid waste,whereas total ammonia nitrogen（TAN）,nitrite（NO₂^--N）and nitrate（NO₃^--N）increased significantly（P<0.05）.Therefore,solid waste should be removed from the tailwater as early as possible,being most optimal within 4 h.Ozone removed 38.24%–48.95%of TSS,17.78%–90.14%of TAN,and87.50%–98.90%of NO₂^--N after 4 h of treatment.However,it resulted in the significant accumulation of NO₃^--N.Moreover,total Vibrio and total bacterial counts in aquaculture tailwater was reduced completely by ozone within 4 h.Therefore,the service time of ozone treatment should not exceed 4 hours.（2）The results of solid waste feed-utilization text showed that compared with before fermentation,probiotic fermentation could improve the sensory characteristics and palatability of solid waste to a great extent.After fermentation,the contents of pathogenicbacteria,including Escherichia coli,Salmonella,and Shigella,decreased significantly,and the contents of probiotics have risen dramatically.The contents of crude protein and crude fat increased significantly.The crude protein content of several fermented feeds increased by about 20%～30%on average;The crude fat content increased by about 1%～4%on average.After fermentation,the content of probiotics in several fermentation liquids increased significantly,and no pathogenic bacteria were detected.During the whole fermentation period,the water quality did not change significantly,and the fermentation liquids were pure.（3）The results of culturing text showed that the survival rate of N.diversicolor in all culturing groups was more than 70%,and all fermented feeds can make N.diversicolor grow.The results showed that higher Highly Unsaturated Fatty Acid（HUFA）levels（mainly EPA and DHA）result in higher survival rates and better growth rates.N.diversicolor fed with EM-feed had the highest DHA and EPA content,and it also had the best growth effect among several fermented feeds.The contents of amino acids and HUFA were higher in all cultured groups,which could meet the needs of aquaculture.The survival rate of Y-Artemia was 22.67±3.40%,which was significantly lower than that of L-Artemia 46.67±3.30%（P<0.05）.The average body weight of Y-Artemia was 1.61±0.07 mg,which was significantly lower than that of L-Artemia 2.05±0.07 mg（P<0.05）.Through fatty acid spectrum analysis,the cultured Artemia is rich in EPA,which can meet the needs of aquaculture fish and shrimp seedlings.The cultured N.diversicolor and Artemia can meet the needs of aquaculture,and providing an effective theoretical basis and data support for the resource utilization and reuse of solid waste.