| In view of the environmental pollution caused by the discharge of a large number of pollutants from aquaculture,biological flocculation technology has been gradually applied in industrial aquaculture.However,when applied to Mariculture animal breeding,it is found that it takes a lot of time to construct a marine biological flocculation reaction system,which not only consumes time,but also increases the cost of mariculture.In order to solve this problem,this paper studies how to construct biological flocculation aquaculture system with different salinity quickly,and preliminarily studies the effect of five fishing drugs on the removal of ammonia nitrogen from bioflocs.The experiment is divided into the following four parts:1.Efficiency of marine biological flocculation aquaculture system cultured by different salinity regulation methodsIn this experiment,the start-up efficiency of three groups of biological flocculation reactors with salinity of 30 cultured by different salinity regulation methods was compared.The first group A was a direct salinity control group: a seawater biological flocculation reactor was constructed in the environment of salinity of 30;the second group B was a slow salinity control group: starting from fresh water,increasing salinity to 30 while cultivating,and then continuing to cultivate bioflocs(from 9 am to 9pm every day,increasing salinity of 1 every 3 hours,increasing salinity of 5 every day until salinity of 30).The third group is the freshwater acclimation group,which is constructed by gradually adjusting and increasing salinity on the cultured freshwater biological flocculation(after the freshwater biological flocculation system is constructed,salt is added every day from 9:00 am to 9:00 pm,salinity of 1 is increased every 3 hours,salinity of 5 is increased every day until salinity of 30).The results showed that the concentration of ammonia nitrogen and nitrite nitrogen in the freshwater acclimation reactor and slow salinity control reactor decreased to a low level before that in the direct salinity control reactor.During the cultivating period,the floc settling volume of freshwater acclimation group was significantly larger than that of other two groups(P < 0.05).High throughput sequencing revealed that Flavobacteria,Sphingobacteria and Actinobacteria were the dominant bacteria in the direct salinity control group and the dominant bacteria in the freshwater domesticated flocculation reactor.Leptobactrium sp.and norank-f-Segniliparacea sp.are the dominant bacteria in seawater biological flocculation reactor with salinity of 30.Combined with the monitoring of ammonia nitrogen removal effect after start-up(there was no significant difference among the three groups(P > 0.05),it was considered that the salinity regulation modes of slow salinity regulation group and freshwater domestication group were beneficial to shorten the cultivation cycle of seawater biological flocculation reactor.2.Start-up of Biological flocculation Reactors with Different SalinityIn this experiment,the way of adjusting salinity at one time was used to study whether the freshwater biological flocculation reactor could be adjusted to a biological flocculation reactor with salinity of 15 and 30 at one time.The first group is the control group: the fresh water biological flocculation reactor does not add salt;the second group in the fresh water biological flocculation reactor one-time increase of salinity of 30 of salt,so that the system becomes a salinity of 30 biological flocculation reactor;the third group in the fresh water biological flocculation reactor one-time increase of salinity of30,so that the system becomes a salinity of 30 biological flocculation reactor.The results showed that the accumulation of ammonia nitrogen and nitrite nitrogen occurred in the experimental group with salinity 30,while in the experimental group with salinity of 15,ammonia nitrogen and nitrite nitrogen remained at a low level.There was no significant difference between the dynamic changes of total nitrogen and total nitrogen in the biological flocculation reactor and the control group(P > 0.05).The floc settling volume of the experimental group with salinity of 15 and 30 was significantly smaller than that of the control group(P < 0.05),and the total suspended solids content of the experimental group with salinity of 30 was higher than that of the experimental group with salinity of 15,which was significantly higher than that of the fresh water group(P< 0.05).High-throughput sequencing of systemic microorganisms: Compared with the control group,there was no significant change in microbial community in the biological flocculation reactor with salinity of 15(P > 0.05),but the abundance of Actinobacteria in the biological flocculation reactor with salinity of 30 increased significantly,and the abundance of Sphingobacteria decreased significantly.At generic level,when salinity was 30,the abundance of norank-f-Segniliparacea sp.increased significantly,while the abundance of norank-f-Saprospiraceae sp.,norank-f-Caldilineaceae sp.and Paracoccus sp.were significantly lower than those of the control group and the biological flocculation reactor with salinity of 30.Monitoring the removal efficiency of ammonia nitrogen in the three treatment groups showed no significant difference(P > 0.05),but the accumulation of nitrite nitrogen in the reactor with salinity of 30 was significantly higher than that in the fresh water group(P < 0.05),but the total accumulation was lower.In conclusion,the biological flocculation reactor with salinity of 15 can be started by directly adjusting salinity in freshwater biological flocculation reactor.3.The effect of salinity on the removal of ammonia nitrogen from the bio-flocculationIn this experiment,the freshwater biological flocculation reactor was adjusted into a biological flocculation reactor with different salinity by adjusting salinity at one time in a freshwater biological flocculation reactor,and then removal effect of 10mg/L ammonia nitrogen was tested.The first group: fresh water bioflocculation reactor without salt,as the control group,the second group directly added salinity to 5 in the fresh water bioflocculation reactor at one time,the third group directly added salinity to10 in the fresh water bioflocculation reactor at one time,the fourth group directly added salinity to 15 in the fresh water bioflocculation reactor at one time,and constructed bioflocculation reactors with different salinity.The results showed that in the experimental group with salinity adjusted to 5,10 and 15,ammonia nitrogen did not accumulate significantly,and the variation trend of tristate nitrogen and total nitrogen was not significantlyt among four groups(P >0.05).The results of high-throughput sequencing analysis showed that the diverse microbial community of the bioflocculation system with salinity of 15 was more higher than other groups,but there was no significant difference in microbial abundance among the four treatment groups(P >0.05).Species composition,the Bacilli sp.,belonging to the Firmicutes and Bacilli,and Actinobacteria no difference between the four treatment groups (P>0.05),The abundance of Norank-f-Caldilineaceae sp.,belonging to the chloroflexi and Caldilineae,was significantly decreased in the system with salinity of 15,while the abundance of Pseudomonas sp.of Proteobacteria,Norank-f-NS9-marine-group sp.,Sphingobacteria and Flavobacteria of Bacteroldetes increased with increase of salinity.Combined with the removal effect of ammonia nitrogen,the effect of the addition of salinity within 15 on the microbial community will not affect the removal of ammonia nitrogen in the system,but also increase the microbial diversity,indicating that the bio-flocculation reactor with salinity within 15 can be constructed by adding salinity once in the fresh water bio-flocculation reactor.4.Effect of five kinds of Fishery drugs on ammonia nitrogen removal ability of Bio-flocculationAdding 4.5 mg/L of sulfadiazine,4.8 mg/L of sulfamethoxypyrimidine,0.45mg/L of flufenicol,1.5 mg/L of doxycycline,15 mg/L of enrofloxacin in the bio-flocculation reactor was used in five common fishing drugs.The control group was a bio-flocculation reactor without fishing medicine.The ammonia nitrogen containing20 mg/L in the influent of the reactor was tested for 20 days.Continuing to add ammonia nitrogen when the content of ammonia nitrogen was reduced.The results showed that the removal efficiency of ammonia nitrogen in fluorine benzene nicol and doxycycline has no Obvious difference Compared to the control group,the cumulants of nitrate nitrogen were 55.10 ±5.89 mg/L and 52.43±2.62 mg/L,It is 47.93±1.70 mg/L in the control group,showing that removal way of ammonia nitrogen still is given priority to nitrifying type in this two reactors,and compared to the control group,these two kinds of fishery drugs significantly reduced the abundance of microbial community,However,it had no significant effect on the structure and abundance of phylum and genus level species(P >0.05).Sulfadiazine had no significant effect on ammonia nitrogen removal and microbial community composition.Sulfadiazine and enoxacin had no effect on the removal of ammonia nitrogen,but the final accumulation of nitrate nitrogen(17.09±10.78 mg/L and 17.14±1.91 mg/L,respectively)was significantly lower than that of the control group(47.93±1.70 mg /L),indicating that the removal of ammonia nitrogen through nitrification was weakened.In addition,these two fishery drugs increased species diversity and reduced community abundance.especially enrofloxacin,It significantly changed the community structure and abundance at the level of species and genera. |
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