| Direct discharge of aquaculture wastewater with high organic matter concentration and high nitrogen and phosphorus content will not only cause surface water pollution and eutrophication,but also damage groundwater and farmland ecosystem,and even endanger human health.In view of the practical problems in the process of resource treatment of aquaculture wastewater,such as the difficulty of effective degradation of organic matter and the difficulty of controlling odor gas,the strains of high-efficient degradation of protein,starch and cellulose were screened from the environment and compounded.The compounded microbial agents were applied to the aerobic fermentation of livestock wastewater to prepare liquid bacterial fertilizer,and the effects of the compounded microbial agents on organic matter in aquaculture wastewater were analyzed.And the removal effect of odor substances.The research results have certain theoretical and practical significance for enriching the resource-based treatment of aquaculture wastewater.The main results are as follows:(1)Eight strains M1,M2,M3,M4,M5,F1,F2 and F3 were screened by transparent circle test of starch,cellulose and protein.It was found that eight strains of bacteria had certain degradability to cellulose,among which M3 had the strongest degradability to cellulose,and produced the largest transparent circle with a HC value of 2.43.Except strain F3,several other strains had certain ability to degrade starch and protein,among which strains M1,M5 and F2 had the strongest ability to degrade starch,HC value reached 3.01,5.35 and 3.62 respectively,strains M1,M2 and F2 had the strongest ability to degrade protein,HC value reached 4.27,3.06 and 3.62 respectively.(2)The amylase,cellulase and protease activities of seven strains of functional bacteria(M1,M2,M3,M4,M5,F1,F2)were analyzed.The protease activities of strains M1,M3 and F2 were significantly higher than those of other strains.The protease activities of strains M1,M3 and F2 reached 58.446U/mL,39.357U/mL and 17.79U/mL respectively,which were much higher than those of other strains.Therefore,M1,M3 and F2 were used as the main strains to degrade protein in aquaculture wastewater.The results of cellulase activity determination showed that strains M1 and F2 had the highest cellulase activity,and strains M2,M3 and M5 also had higher cellulase activity.In the amylase determination experiment,seven strains had the ability to decompose starch.Strains M1,M2,M3,M5 and F2 had the stronger ability to decompose starch.The highest activity of strain M5 was 0.97U/mL,which was 2-3 times that of other strains.The protease,cellulase and amylase activities of seven strains were compared.Strains M1,M2,M3,M5 and F2 were selected as functional strains in the experiment of resource disposal of aquaculture wastewater.(3)Molecular biological identification of the strains identified by re-screening showed that strains M1 and M5 were Aspergillus Niger,M2 was Fusarium equiseti,M3 was Bacillus subtilis,and F2 was Phialemonium sp.(4)In order to prepare composite microbial agents,the growth curves of five functional microorganisms were determined.Bacillus subtilis M3 entered logarithmic phase at about 12 hours,stable phase at about 20 hours,and declined after 28 hours.Two strains of Aspergillus Niger M1 and F5 entered logarithmic phase only after 40 hours,and began to enter stable phase around 48 hours.The stable period of Aspergillus Niger lasted for a long time and showed a significant downward trend at 60 h.Compared with M1 and M5,the logarithmic phase of Phialemonium sp.F2 entered earlier and the stable phase lasted longer.It began to decline after about 76 hours.Fusarium equiseti M2 enters logarithmic phase at about 18 hours,microorganisms multiply rapidly and enter stable phase at about 28 hours.(5)In order to better compound the selected strains and apply them to the practical application of aquaculture wastewater resource treatment,the deodorization and organic matter degradation ability of the compound bacterial agent were studied by measuring the content of odor substance,protein content and COD concentration during fermentation process by mixing the compound bacterial agent with the aquaculture wastewater in different dosage in the reactor.Through the experimental study,it was found that when the volume of fungi and bacteria was compounded according to 1:1,the effect of compound fungi agent on aquaculture wastewater treatment was better under the condition of 3% inoculation.The 30-day removal rates of indole,deodorizer,ammonia and hydrogen sulfide reached 79.0%,69.0%,96.8% and 79.2%,respectively.The degradation rate of protein reached 54.04% in 30 days and the removal rate of CDO reached 65.1%.A large amount of organic nitrogen was converted into inorganic nitrogen salt.The results showed that the compound microbial agent not only had obvious deodorizing ability,but also had the ability to remove organic pollutant.(6)The composite microbial agent was applied to the resource treatment of aquaculture wastewater.The results showed that the contents of hydrogen sulfide,ammonia,indole,trimethylindole and other odorous substances decreased significantly,and the removal rates reached 66.3%,95.2%,81.1% and 75.0% respectively in 30 days.The COD degradation rate was 62.5%,the protein degradation rate was 58.3%,and the total nitrogen content was 1.16 times higher than that at the beginning of the reaction,which indicated that a large amount of organic nitrogen and ammonia nitrogen were decomposed by microorganisms into nitrate nitrogen which could be absorbed by crops.In addition,the soluble phosphorus content was 1.22 times higher than that at the beginning of the reaction.After 30 days of fermentation,the number of bacteria and fungi in wastewater was much larger than that stipulated by the national standard for liquid organic fertilizer.Escherichia coli faecalis decreased from 4650 cfu/mL to 110 cfu/mL,which basically met the national standard for organic fertilizer(100 cfu/mL),but still needed to be improved. |
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