| 1.Ammonia nitrogen treatment capacity and nutrient composition of floating and sinking bioflocTo explore the ammonia nitrogen treatment capacity and nutrient composition of sinking flocs and floating flocs with and without carbon source.Under the two conditions,three treatment groups were set up respectively-sinking flocs,mixed flocs and floating flocs.Each groups of TSS(Total Suspended solid,TSS)was about 150mg/L and alkalinity was about 300.00 mg/L,10 mg/L NH4 Cl was used as the nitrogen source and glucose with DOC/TN=15 was used as the carbon source.A 3-day continuous water quality monitoring test was carried out.At end of the test,flocs were taken to measure the nutritional indicators.The results showed that the total ammonia nitrogen removal rate of sinking flocs,mixed flocs and floating flocs with carbon source were(1.03±0.03)mg/g·h and(1.00±0.01)mg /g·h,(1.05±0.07)mg/g·h;the removal rate of ammonia nitrogen for sinking flocs,mixed flocs and floating flocs without carbon source were(1.20±0.16)mg/g·h,(1.28±0.03)mg/g·h,(1.02±0.03)mg/g·h,ammonia nitrogen removal rate for sinking flocs and mixed flocs without carbon source was higher than the sinking flocs and mixed flocs with carbon source and the difference in the ammonia nitrogen removal rate of the floating flocs between the two groups is not significant.The nitrite nitrogen(NO2--N)of the floating flocs has a higher peak concentration,which is(1.85±0.05)mg/L under the condition of adding carbon source and(3.32±0.38)mg/L which are under the condition of not adding carbon source,the final concentration of nitrate,total nitrogen and dissolved total nitrogen of sinking flocs,mixed flocs and floating flocs in the groups which are with carbon source and without carbon source were significantly different(P<0.05).With the addition of carbon source,the floating flocs have more content of Eicosapntemacnioc Acid(EPA)and fatty acids.Without the addition of carbon source,the sinking flocs have more content of amino acids and floating flocs had a higher content of EPA.The results showed that the sinking flocs have a better capacity for removeing TAN and NO2--N,the floating flocs had a higher nutritional value.2.The effect of floating flocs on the growth of tilapiaIn order to explore the effect of floating flocs on the growth of tilapia in breeding.In this experiment two treatments were designed namely the control group and the floating floc group.The TSS of each group approximately was 400 mg/L and alkalinity was maintained at about 250.00 Ca CO3/L.Tilapia were cultured at an initial density of 100 fish/m3.During the experiment,the peak concentrations of the normal nitrite group and the floating floc group were(0.07±0.06)mg/L,(0.19±0.03)mg/L respectively.Total nitrogen,total phosphorus,total dissolved nitrogen,total dissolved nitrogen and total dissolved nitrogen had the same change trend.The weight gain rate of tilapia in the control group and the floating floc group were 1.95±0.11 and2.01±0.07,respectively;the specific growth rates were(654±4.00)% and(656±2.00)%,respectively;The feed coefficients were(125±7.00)%,(121±4.00)%;the survival rates were(89.00±2.00)%,(94.00±2.00)%;the terminal densities were(3.67±0.35)kg/m3,(3.48±0.11)kg/m3,the terminal density of the control group was higher than that of the floating floc group,all other growth indicators are lower than that of the floating floc group.The crude protein of the control group was higher than that of the floating floc group and the crude fat was lower than that of the floating floc group.the results showed that two kinds of bioflocs had no obviously different in breeding tilapia.3.Effects of sinking flocs and floating flocs on the growth of tilapia and microbial communityIn order to explore the effects of sinking flocs,floating flocs and normal flocs on the growth effect of tilapia and microbial community,three treatments were designed in this experiment,namely group A(control group)and group B(floating floc).flocculation group)and C group(sinkable flocculation group),three parallels for each group were 1,2,3,the TSS is maintained at 250mg/L and the alkalinity is maintained at about 250.00 Ca CO3/L.Each groups was(549.86 ± 0.92)g of tilapia at the beginning and fed fish food which over the tilapia demands for 47 days.The experiments was carried out for 47 days.The water quality was measured every 2days and the TSS was measured every 7 days.The results showed that the fluctuation of ammonia nitrogen and nitrite in the sinking floc group was higher than that in the floating floc group and higher than that in the control group.The peak concentrations of ammonia nitrogen in the three groups were A group(2.11±1.35)mg/L,B group(1.70±0.26)mg/L and C group(1.83±2.30)mg/L and the peak concentrations of nitrite in the three groups were A group(0.46±0.05)mg/L,B group(0.43±0.04)mg/L and C group(0.35±0.02)mg/L,the difference was not significant(P<0.05),The fluctuation and peak concentration of the five indicators such as TN,TP,DTN,DTP and PO4-were that the floating flocs are higher than the control group than the sinking flocs;At the end of the experiment,the species richness in the bioflocs of the control group was higher than floating flocs group than sinking flocs group,the diversity index in the bioflocs of the floating flocs group was higher than control group higher than sinking flocs group;The sinking floc group dominant bacteria were Proteobacteria(47.78%),Bacteroidetes(17.96%)and Planktophytes(12.45%),the floating floc group dominant bacteria were Proteobacteria(34.24%),Planctomycetes(13.00%),Bacteroidetes(9.99%)and Fusobacterium(21.62%),the control group dominant bacteria were Proteobacteria(36.53%),Bacteroidetes(17.59%)and Fusobacterium(13.80%).The dominant bacteria in the tilapia gut of the control group were Planktophytes(57.39%)and Proteobacteria(27.60%),the dominant bacteria in the tilapia gut of floating flocs group were Planktophytes(86.18%),Proteobacteria(7.11%),the dominant bacteria in the tilapia gut of normal flocs group were Planktophytes(59.02%)and Proteobacteria(23.75%);the growth situation and indicators of the tilapia in the sinking floc group were better than those in the control group and than the floating floc;the nitrogen utilization rate varied from high to Low is control group > sinking floc group > floating floc group,and phosphorus utilization rate is sinking floc group > control group > floating floc group. |
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