Water Purification Effect And Economic Analysis Of Internal Circlation Culture System Of Litopenaeus Vannamei Based On Polyurethane Biofilm

The regulation of the water quality of cultured water bodies is the key to the success of Litopenaeus vannamei culture.The traditional pond aquaculture mode is mainly realized by changing water,which not only consumes a lot of water resources,but also mostly discharges directly without treatment,causing pollution to the environment.Recirculating aquaculture（RAS）is an efficient aquaculture model that has been developed in recent years.This model can improve the utilization rate of water resources,reduce wastewater discharge,and increase aquaculture production at the same time.However,it has problems such as high investment and operating costs and is difficult to promote in a large area.This research group proposed an internal circulation prawn farming model,built in the prawn farming pond with pre-filmed polyurethane bio-filler,making full use of the prawn farming pond space,integrating the prawn farming pond and water purification in one,with low investment and operating costs,High density,high output,prevent the invasion of foreign pathogenic bacteria,reduce the incidence of shrimp and other advantages.This paper studies the water purification effect and economic analysis of the internal circulation culture system of Litopenaeus vannamei based on the polyurethane biofilm.Scanning electron microscopy and high-throughput technology are used to analyze the morphology and bacterial community structure and diversity of the polyurethane filler biofilm in the internal circulation culture system.The following conclusions are obtained through research:（1）Set up 4 standard seedling systems for changing water desalination salinity（A₁）,changing water without desalinating salinity（A₂）,internal circulation desalination salinity（A₃）and internal circulation without desalination salinity（A₄）.During the 22-day standard seedling process,the temperature,DO and p H meet the requirements of the shrimp standard seedlings.In terms of turbidity,the standard seedling pond that uses the internal circulation method and does not desalinate salinity was the highest.For ammonia nitrogen,nitrite nitrogen,nitrate nitrogen and total nitrogen,the ammonia nitrogen concentration and water exchange system in the water body using the internal circulation system standard seedling method were lower,and the nitrite nitrogen concentration was lower than that of the water exchange system.The concentration of nitrate nitrogen and total nitrogen in the water body of the circulatory system standard seedling method was higher than that of the water exchange system.The concentration of ammonia nitrogen,nitrite nitrogen,nitrate nitrogen and total nitrogen in the system desalinating salinity during the standard seedling process were all higher Does not dilute the low salinity.In terms of total phosphorus and COD,the total phosphorus and COD concentrations in the water body using the internal circulation system standard seedling method were higher than those in the water exchange system.The total phosphorus and COD concentration of the system desalinated salinity during the standard seedling process were both higher than that of the non-desalinated salinity low.In terms of shrimp growth,the internal circulation culture system based on polyurethane biofilm could improve the success rate and body weight of shrimps.At the same time,the growth of shrimps with desalinated salinity was worse than that of shrimps without salinity,and the difference was obvious.（2）Set up 6 aquaculture systems（B₁,B₂,B₃）and internal circulation system（B₄,B₅,B₆）.During the 60-day breeding process,the temperature,DO and p H of the shrimp breeding process met the shrimp breeding requirements.In terms of turbidity,the internal circulation system was higher than the circulating water system.For ammonia nitrogen,nitrite nitrogen,nitrate nitrogen,and total nitrogen,the concentration of ammonia nitrogen in the aquaculture water using the internal circulation system and the circulating water system were lower.The concentration of nitrite nitrogen was higher than that of the circulating water system.The internal circulation system was used in the aquaculture water.Nitrate nitrogen and total nitrogen concentration were lower than the circulating water system.In terms of total phosphorus and COD,the concentration of total phosphorus and COD in the water body of the internal circulation system was lower than that of the circulating water system.In terms of shrimp growth,the survival rate of prawns cultured by the internal circulation system was significantly higher than that of the circulating water system,indicating that the internal circulation culture system based on polyurethane biofilm can increase the survival rate of prawns.The average body length and average weight of prawns cultured in the internal circulation system were higher than those of the circulating water system.（3）Through electron microscopy analysis,clear pores could be seen in the polyurethane filler without film,and no microorganisms are attached;after the film was coated,a large number of microorganisms were attached to the surface of the filler,mostly in the form of bacterial micelles;The number of surface microorganisms was higher than that in the early and middle stages,mainly including spherical bacteria,rod-shaped bacteria and filamentous bacteria.The richness and diversity of bacterial community structure of polyurethane filler samples in different culture ponds were different.For bacterial community richness analysis,the OTU dilution curve showed that when the number of samples reaches 35,it indicated that the storage capacity covers most of the bacterial flora at the site;αdiversity analysis included shannon,simpson,ace,chao,coverage index.It showed that the B₄ had a high diversity of bacterial communities on the surface of the unwashed polyurethane filler.At the phylum level,Proteobacteria,Bacteroidetes,Firmicutes,and Planctomycetes were all dominant phyla in different systems.For dominant bacteria,the dominant bacteria in B₄ were Pseudomonas,Xanthomarina,Rheinheimera,and Cellvibrio,while the dominant bacteria in B₅ were mainly the genus Fusiformis（Fusibacter）and unclassified＿c＿＿Deltaproteobacteria,etc.（4）There was a significant difference in the total cost of the two modes of internal circulation and circulating water.The total cost consists of two parts,the cost of infrastructure construction and the daily operating cost of the system.For the two culture modes,the total cost of Litopenaeus vannamei in a cycle（100 d）was calculated,the target seedling density is 15,000/m³,and the target seedling period was20 d;the breeding density was 800/m³,and the breeding cycle.It was 80 days,the researched aquaculture water body was 1000m³,the total cost of using circulating aquaculture was（?）1,901,600,the cost of infrastructure construction was（?）1,872,500,the daily operating cost of the system was（?）29,100,and the total cost of using internal circulation aquaculture was（?）555,700,the cost of infrastructure construction was（?）532,500,and the daily operating cost of the system was（?）23,200.The main difference between the two types of costs lied in the cost of infrastructure construction.The internal circulation system equipment required less investment and was easy to modify.There was no need for biochemical tanks,microfilter protein separators and other equipment,so the total cost of the internal circulation system was lower.