| 1.Effects of different floc particle sizes on efficiency of ammonium removal and bacteria community of biofloc.The ammonium removal and bacteria community efficiency of bioflocs with<50?m particle size,>50?m particle size and un-sieved bioflocs,referred as group A,group B and group C were investigated in the current experiment.The removal rate of total ammonium nitrogen?TAN?for the group A,B and C were 2.44±0.29,2.49±0.23,and 2.41±0.03 mg TAN/g TSS·h,respectively.No significant difference of the removal rate of TAN among the three groups was observed?P>0.05?.The syndrome of TAN,nitrite nitrogen and nitrate nitrogen were resembled to the start-up of autotrophic nitrification and no significant difference of concentrations were found among the three group.C/N ratio of>50?m bioflocs is higher than that of the other groups.No significant difference of crude protein content in flocs were found among the three groups.The bacterial community structure development of bioflocs was analyzed by Illumina MiSeq sequencing analyzes.Bacteria community composition of the floc group of different particle sizes was similar at the level of phylum and class,mainly identified belonged to 6 classes?abundance up to more than 5%?:Bacilli,?-proteobacteria,Actinobacteria,Caldilineae,Anaerolineae,and Sphingobacteriia.At the genus level,the population of Bacilli were dominant in all the three groups.Bacteria community of group B is 26.0%of Bacilli genus,which was significantly higher than the other two groups.2.Effects of different particle sizes of flocs on nitrification in Biofloc-aquaculture systemsThe ammonia conversion capacity of the bioflocs with<50?m particle size,>50?m particle size and un-sieved bioflocs.It showed that there was no significant difference in the assinilation removal rate of ammonia nitrogen with different size flocs?P>0.05?.The bacterial community structure of bioflocs was analyzed by Illumina MiSeq sequencing analyzes.The results showed that the microbial community composition of the floc group of different particle sizes was similar at the level of phyium,class and genus.The main bacteria in the process of biofloc culture belonged to 6 classes:Actinobacteria,?-proteobacteria,?-proteobacteria,?-proteobacteria,Bacilli,and Sphingobacteriia.The population of Firmicutes?Bacilli?of the<50?m particle size group?Bacillus?was significantly higher than the other two groups.The addition of carbon source can improve the stability and cushioning of the microbial community,and the microbial community diversity decreases significantly with the decrease of DOC.3.Effect of carbonhydrate addingstrategy and flocs level on the establishment of nitrification in Bioflocs systemIn this experiment,the effects of three carbon source addition strategies and two floc concentrations on the construction of biofloc system and the formation of stable nitrification were investigated.The three carbon source addition methods were as follows:Group A was adding glucose according to DOC/TN=20 at one time;Group B was adding glucose according to DOC/TAN=20 when total ammonia nitrogen?TAN?was higher than 2 mg·L-1;Group C is a polycaprolactone?PCL?hanging bag group.The flocculation volume was characterized by total solid suspended particulate matter?TSS?concentration,and the initial TSS concentrations were 300 mg·L-11 and 800mg·L-1,respectively.The results showed that the average concentration of DOC in each treatment group was significantly different from DOC/TN and DOC/DIN in water?P<0.05?.TSS had no significant effect on the time of nitrification process and the comprehensive characteristics of tri-state nitrogen.The carbon source addition method has a significant impact on the time of the nitrification process and the comprehensive characteristics of the tri-state nitrogen and the highest concentration.Different TSS concentrations and different carbon source addition methods have a significant effect on the extreme value of the three-state nitrogen.The effect of carbon source addition on pH and alkalinity was not significant.The floc group with TSS concentration of 300 mg·L-11 had higher average pH and alkalinity than the floc group with TSS concentration of 800 mg·L-1?A3>A8,B3>B8,C3>C8?.The alkalinity of A3 and A8 groups was lower than that of B3,B8 and C3,C8 groups;TSS concentration had no significant difference with dissolved oxygen,and the carbon source addition method had significant effect.The way of adding carbon source and the amount of floc did not significantly affect the crude protein,crude ash and VSS in the floc.In general,the abundance and diversity of species of A carbon source addition method were higher than the other two methods.Among the A carbon source addition method and the C carbon source addition method,the TSS concentrationsof300 mg·L-11 is slightly higher than 800 mg·L-1.The way in which B carbon sources are added is the opposite.The concentration of floc and the way of adding carbon source have significant effects on the horizontal composition of the floc group.The relative abundance of Nitrospirae?1.3%?in group A3 is significantly higher than that in group B3?0.7%?and C3?0.1%?.Similar to the change in tri-state nitrogen,nitrification is more pronounced.The carbon source addition method has a significant effect on the horizontal composition of the floc group,and the floc concentration has no significant effect on the horizontal composition of the floc group.4.Effect of carbonhydrate addingstrategy and flocs level on the bleeding effect of Clarias leather in Bioflocs systemIn this study,we cultured Clarias leather with three carbon source addition methods and two flocs level.Since the TAN in group B did not increase to more than2 mg·L-11 during the cultivation period,no glucose was added in the experiment cycle of group A and group B,and only PCL bag was used in group C to provide carbon source.The flocs level was characterized by the concentration of TSS,which was regulated by two gradients:TSS 300 mg·L-11 group and TSS 800 mg·L-1group.To explore the effects of different carbon source addition methods and flocs level on the aquaculture system of Clarias leather,nitrogen conversion and microbial community in biofloc system.The initial stocking density of each aquaculture tank was?0.7±0.23?kg·m-3.At the end of the experiment,the final density of Clarias leather ineach group was A3:?12.98±1.10?kg·m-3,B3:?13.98±0.78?kg·m-3,C3:?15.46±0.83?kg·m-3.A8:?11.94±0.26?kg·m-3,B8:?14.11±1.03?kg·m-3,C8:?14.46±0.50?kg·m-3,there was no significant difference between the treatment groups?P>0.05?.Itshowed that the survival rate of all groups reached above 88%,which wereA3:?88.8±11.7?%?B3:?91.1±1.5?%?C3:?94.4±1.5?%;A8:?92.2±2.1?%?B8:?94.4±2.1?%?C8:?96.7±1.0?%.The survival rate of TSS 800 mg·L-11 group was higher than that of TSS 300 mg·L-11 group,and lower than that of TSS 300 mg·L-1group.There was no significant difference in crude ash content?P>0.05?.There was no significant difference in TSS fluctuation of floc under the same TSS concentration regulation?P>0.05?.At the end of the experiment,the settlement volume of flocs in group C was significantly lower than that in groups A and B?P<0.05?.At the same TSS concentration of flocs,there was no significant difference in the relative abundance of each treatment group at the phylum level?P>0.05?.The results of this part of the experiment show that within the appropriate TSS concentration range,the higher TSS concentration is more suitable for the growth and survival of leatherbeard catfish,while the lower TSS concentration has a greater impact on the water quality fluctuation.C carbon source addition method?PCL hanging bag?continued to provide carbon source,which had better effect on bio-floc breeding of Clarias leather than the other two methods. |
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