Development And Application Effect Test Of An In-situ Purification Device For Aquaculture Water

As the demand for aquiculture products is increasing,the culture mode gradually changed to the intensive culture mode of high density and high feeding,and this culture way will lead to the decreasement of dissolved oxygen in the water and the continuously enrichment of nutrients,causing water quality deterioration in turn.It not only influents the sustainable development of the breeding industry itself,but also adversely affects the surrounding water environment and ecosystem.In addition,with the gradual improvement of the national culture tail water discharge standards and the continuous strengthening of management measures,how to make the culture tail water reach the standard for discharging has attracted more and more attention from the government and society,so looking for a new type of culture water purification technology seems imminent.1.The design and manufacture of in-situ purification equipment for culturewaterThe in-situ purification device who takes the microbial attachment base as the core and has an ability of floating on breeding water is designed and manufactured based on the ecological characters that the nitrifying bacteria,phosphorus-accumulati-ng bacteria etc.microbe distribut in natural water and have the ability to adsorb on the surfaces of solid,and even can absorpt the ammonia nitrogen,nitrite nitrogen,phosphorus etc.in water for reproduction and growth.It contains 5 parts: stents and other components to float,cultch of microorganism,upflow system,bottom-oxygen-increasing system,air supply system energied by photovoltaic power generation.The device has an advantage of powerful purification function with a compact structure,and it will has a wide application range.2.Microbial membrane construction and purification effect test of in-situ purification device for cultured waterThe purification efficiency on ammonia nitrogen,nitrite nitrogen,nitrate nitrogen and total phosphorus in culture water was studied in the process of biofilm construction and its completion in the freshwater and seawater environment with ammonia nitrogen concentration grade of 1 mg/L,3 mg/L and 5 mg/L.The results shows that:when under the condition that the temperature is 22?25?,the dissolved oxygen is 6?9mg/L,the p H is 7.0?8.5,the biofilm construction in freshwater test groups with different ammonia nitrogen concentrations complete in the 16 days,and there is no significant differences(P<0.05)in each test group in the daily reduction of ammonia nitrogen,nitrite nitrogen,nitrate nitrogen,total phosphorus during the biofilm construction process.For example,on the 18 th day,the daily reduction of ammonia nitrogen in the three groups with the concentrations of 1mg/L,3mg/L,and 5mg/L respectively are 304.587 g,283.748 g and 314.753 g;and the daily reductions in nitrite nitrogen respectively are 297.032 g,292.566 g and 304.256 g,the daily outputs of nitrate nitrogen respectively are 297.934 g,276.239 g and 312.108g;the daily reductions of total phosphorus respectively are 0.485 g,0.427 g and 0.462 g.when under the condition that the temperature is 27??31?,the dissolved oxygen is 6mg/L?8mg/L,the p H is 7.0?8.5,the biofilm construction of the seawater test groups with different ammonia nitrogen concentrations complete in 21 days.There exists significant differences(P>0.05)between different ammonia nitrogen concentrations in the daily reduction of ammonia nitrogen,nitrite nitrogen,nitrate nitrogen during biofilm construction.For example,on the 24 th day,the daily reduction of ammonia nitrogen in the groups with ammonia nitrogen concentration grade of 1mg/L,3mg/Land5mg/L respectively are 243.327 g,258.132 g and 279.372g;the daily reductions in nitrite nitrogen respectively are 231.974 g,256.479 g and 284.273g;the daily output of nitrate nitrogen respectively are 243.16 g,271.905 g and 285.505g;the reduction capacity of the device for ammonia nitrogen and nitrite nitrogen and the production capacity for nitrate nitrogen both increase as the ammonia nitrogen concentrations increase.However,the daily reduction of total phosphorus in different concentration gradients are not significantly different(P>0.05).For example,on the 24 th day,the daily reduction respectively are 0.566 g,0.595 g and 0.493 g.In summary,after stable operation,the device maintains a strong purification capacity for ammonia nitrogen,while the purification effect for total phosphorus is much less than that for the tri-state nitrogen.3.Analysis about the microorganism's biotic community and its functionIn this study,high-throughput sequencing technology is used to carry out flora analysis on carrier biofilm for both the distance of 10 cm,45cm,80 cm as 3 water layers below the water surface in fresh water and seawater when ammonia nitrogen concentration gradient is 3mg/L and the distance of 45 cm below the water surface when ammonia nitrogen concentration gradient are 1mg/L,3mg L,5mg/L.The results show that:when compared in terms of species richness,species diversity,and similarity coefficient of species composition in freshwater,the three water layer samples from device shows that the difference between the middle and lower layers is small(P>0.05),and the two are both more abundant than the upper layer.At the phylum level,the three sample bacteria mainly consisted of Proteobacteria and Nitrospirae,and the proportions of Proteobacteria in the three samples are not significantly different(P>0.05).Nitrospirae in the middle layer samples is slightly higher than the upper and lower layers,and the proportions of the upper and lower layers are not significantly different(P>0.05);At the genus level,a total of 5 species of nitrifying bacteria and 14 species of phosphorus-accumulating bacteria are detected out in the three samples,of which the nitrifying bacteria includes Nitrosomonas,Nitrosospira and Nitrosococcus,Candidatus?Nitrotoga and Nitrospira.What's more,in the study,the 5 species are shared by all 3 samples,in which ammonia oxidizing bacteria(AOB)bacteria's proportion of the three groups respectively are 16.88%,17.88%,12.40%and the proportion of nitrite oxidizing bacteria(NOB)bacteria groups respectively are 52.54%,54.86%,49.18%,and the two both show a trends of middle layer>upper layer>lower layer inproportion.The proportions of Phosphorus in the three samples respectively are 2.79%,2.52%,3.46%,showing a trends of lower layer>upper layer>middle layer in proportions.when compared in terms of species richness,species diversity,and similarity coefficient of species composition in seawater,the samples in the lower water layer of the device are not significantly different(P>0.05),while the upper layer has more abundant species;meanwhile in the aspects of species richness,species diversity,and similarity coefficient of species composition 3mg/L samples> 1mg/L samples(5mg/L sample flux detection error,no reference).At the phylum level,the four sample flora mainly consisted of Proteobacteria and Nitrospirae,of which the proportion of Proteobacteria was not significantly different(P>0.05).Nitrospirae is slightly higher than the upper and lower layers,and the proportion of the 1mg/L sample is the smallest;at the genus level,a total of 6 species of nitrifying bacteria and 13 species of phosphorus-accumula-ting bacteria are detected in 4 samples,of which nitrifying bacteria include Nitrosomonas,Nitrosospira,Nitrosococcus,Nitrospira,Nitrospina and Nitrococcus,the 6 species are shared by all 4 samples,in which ammonia oxidizing bacteria(AOB)bacteria's proportion of the four groups respectively are 20.60%,22.04%,21.70%,and 22.07%,showing middle layer> lower layer>upper layer,and the difference between the 1mg/L group and the 3mg/L group is not significant(P>0.05);And the proportion of nitrite oxidizing bacteria(NOB)bacteria groups respectively are 51.46%,56.32%,55.37%,and50.77%,showing middle layer>lower layer>upper layer,3mg L group>1mg/L group.The proportions of Phosphorus in the four samples respectively are 3.71%,3.52%,3.02% and 2.85%,showing upper layer>middle layer>lower layer,3mg/L group>1mg/L group.In summary,after the biofilm construction of the freshwater and seawater installations is completed,the microbial communities in the middle and lower water layers have little difference in species abundance,species diversity,and similarity of species composition;The proportion of the group is higher than that of the upper and lower water layers.The higher the ammonia-nitrogen concentration gradient in the freshwater and seawater tests,the greater the overall proportion of nitrifying bacteria.The total proportion of phosphorus accumulating bacteria in the desalination plant is much smaller than that of nitrifying bacteria.