Construction And Operation Effect Of Self-circulation Penaeus Vannamei Aquaculture System Based On Substrate Selection And Probiotics Combination

In recent years,the prawn aquaculture industry in China has developed rapidly,the output and scale of aquaculture have been ranked first in the world for many years.However,the current model of aquaculture causes environmental pollution and disease outbreaks,which affects the green and sustainable development of the aquaculture industry.The pond culture has been the main method of shrimp aquaculture in China.The study found that the production of 1 kg of prawns by aquaculture system needs to consume 20 tons of clean water.Most of the waste water generated in the process of aquaculture is directly discharged without treatment,resulting in the deterioration of aquaculture water environment and the outbreak of prawn disease.Even can directly kill the prawns.In recent years,the Rcirculating Aquaculture Systems has been widely studied and applied in factory farming.However,the system has a large investment,and the system has high operation and management costs.Biofloc is formed by bioflocculation and adding an organic carbon source.BFT can adsorb the suspended organic solids in the aquaculture water and purify the water by microbial assimilation.Although BFT can reduce water exchange and reduce environmental pollution,management technology and operations technology requirements are not conducive to large-scale popularization.In order to solve the existing problems in aquaculture,a self-circulation prawn culture system was constructed by screening highly effective biofilm carrier and adding microecological preparations.The self-circulation prawn culture system can make full use of the space of aquaculture pool.The process of the system is simple,the land area used is small,and the space utilization of the system is high.This system can not only has the function of shrimp culture,but also can purify the water quality of aquaculture.Research contents include:（1）The establishment process of biofilm systems with different biofilm carriers and the removal efficiency of ammonia nitrogen and nitrite nitrogen were compared and studied,（2）Effect of microecological preparation on the establishment of nitrification function in mariculture system,（3）Purification of water quality in shrimp aquaculture systems and growth of shrimp by self-circulating shrimp culture systems were studied.（1）Biofilm culture systems were constructed by adding seven kinds of substrates such as crushed coral,fiber ball,MBBR,levitated sphere（spongia）.Eight different mariculture systems were constructed by adding nitrifying bacteria,the effects of different substrates on the nitrification process were studied.The establishment of nitrification function is related to the performance of biofilm carrier and the growth characteristics of nitrifying bacteria.The degradation of ammonia nitrogen in aquaculture systems with crushed coral,fiber ball and levitated sphere（spongia）as biofilm carriers took 4 days,6 days and 11 days,respectively.The ammonia oxidation intensity is 6.97,4.97 and 3.03 times of the blank control system.The removal effect of system ammonia nitrogen is better than that of other systems with other substrates added.The degradation of nitrite nitrogen in aquaculture systems with crushed coral,fiber ball and levitated sphere（spongia）as biofilm carriers took 10 days,18 days and21 days,respectively.The highest concentrations of nitrite nitrogen were 3.06 mg/L,3.12 mg/L,and 3.67 mg/L,which required 10 d,18 d,and 21 d to be removed,respectively.The promoting effect of biofilm carrier on the establishment of biofilm systems is crushed coral>fiber ball>levitated sphere（spongia）>ceramic grain filters>MBBR>levitated sphere（ribbons）>biological rope packing.（2）Nine different mariculture systems were constructed by adding crushed coral,fiber ball and ceramic grain filters.Three different placement were used for the same biofilm carrier,and effects of different placement of substrates on nitrification function were compared.Fiber balls using nonwoven fabrics（100 mesh sieve）is better than hanging with a net bag and Nonwoven fabrics（200 mesh sieve）.The ammonia nitrogen in the culture systems can be removed 2 days and 7 days earlier,respectively.The nitrification function of the culture systems was established 1 days and 9 days earlier,respectively.The ammoxidation intensity of the former system was1.19 mg/L.d^-1 and 3.13 mg/L.d^-1 higher than the latter.The effect of ceramic grain filters placed in the net bag is better than that of the bottom placement and the nonwoven fabrics（100 mesh sieve）.The ammonia nitrogen in the culture system can be removed 8 days and 6 days earlier,respectively.The ammoxidation intensity of the former system was 1.63 mg/L.d^-1 and 1.57 mg/L.d^-1 higher than the latter.The ceramic grain filters was placed on the bottom and the nonwoven fabrics（100 mesh sieve）,and the aquaculture systems was simultaneously completed to remove the nitrite nitrogen within 25 days.It takes 25 days to complete the removal of nitrite nitrogen in the envelop hanging mode of ceramic grain filters.The ceramic grain filters hanging with a net bag is more advantageous to the establishment of nitrification function.MBBR using nonwoven fabrics（100 mesh sieve）is better than hanging with a net bag and Nonwoven fabrics（200 mesh sieve）.The ammonia nitrogen in the culture system can be removed 2 days and 7 days earlier,respectively.The nitrification function of the culture systems were established 6 days and 4 days earlier,respectively.The ammoxidation intensity of the former system was 2.11 mg/L.d^-1 and 1.87 mg/L.d^-1higher than the latter.（3）By adding the three kinds of probiotics including nitrifying bacteria,photosynthetic bacteria,Bacillus subtilis and the fiber balls as biofilm carrier,using the man made sea water to build four mariculture systems.The nitrification processes and nitrification intensity of different mariculture systems were compared and analyzed.In the aquaculture system with the same biofilm carrier,the nitrification function of the nitrifying bacteria+Bacillus subtilis systems was established 12 hours ahead of the nitrifying nitrifying bacteria+photosynthetic bacteria systems.After the nitrification function of the system is strengthened,the ammonia oxidation intensity was 1.69 mg/L.d^-1 and 1.36 mg/L.d^-1,respectively.The highest concentrations of nitrite nitrogen were 1.21 mg/L,1.12 mg/L,which required 36 h,18 h to be detected,respectively.In the seawater aquaculture systems with the same microecological preparations,the nitrification function of the the biofilm system with fiber balls as the biofilm carrier was established 24 hours in advance.The nitrification intensity of the biofilm system is higher than that of the biofloc system.The addition of a carbon source can accelerate the establishment of nitrification function of the syste m of nitrifying bacteria+Bacillus subtilis,but reduces the nitrification intensity of the system.（4）Six aquaculture systems were constructed by adding fiber balls,MBBR and crushed coral as biofilm carriers,The low density aquaculture systems and high density aquaculture systems aquaculture systems were established using the same biofilm carrier.The concentration of ammonia nitrogen was maintained below 0.60mg/L during the production process in the biofilm aquaculture systems with different biofilm carriers.The highest concentration of ammonia nitrogen in low density aquaculture systems and high density aquaculture systems with fiber balls was 0.51mg/L and 0.56 mg/L,respectively,and the crushed coral systems were 0.48 mg/L and0.49 mg/L,respectively.The concentration of ammonia oxygen in the culture system of the same biological carrier did not differ significantly.The nitrification function of crushed coral aquaculture system is better than that of fiber balls aquaculture system.The highest concentration of ammonia nitrogen was 0.17 mg/L higher in the MBBR high density aquaculture systems than that in the low density aquaculture systems system.The seawater aquaculture system with MBBR had poor degradation of ammonia nitrogen in the later stage of the production process.The concentration of nitrite nitrogen in the low density aquaculture systems and the high density aquaculture systems with coral bone as the biofilm carrier is similar,and can be maintained below 0.5 mg/L in the later stage of the production process.The concentration of nitrite nitrogen in the high density aquaculture systems of fiber balls and MBBR is higher than that in the low density aquaculture systems using the same substance.The concentration of nitrite nitrogen in the MBBR culture system increases in the late stage of production,and nitrification function of the systems is bad.（5）The survival rates of low density aquaculture systems and high density aquaculture systems with fiber bulbs,fluidized bed packing and coral bones were68.1%,59.0%,65.9%,40.0%,80.0%,72.0%,and the feed coefficients were 1.18,1.38,1.39,1.52,0.87,1.08,respectively.The high density aquaculture systems with coral bones has a survival rate of 12%and 14%higher than the low density aquaculture systems with fiber balls and MBBR as biofilm carrier,respectively.The survival rate and yield of shrimp are higher in the self-circulating systems than the other biofilm carrier in the application of crushed coral as a biofilm carrier.The low density aquaculture systems with crushed cora,fiber ball and MBBR as biofilm carrier has a survival rate of 9%,26%and 8%higher than the high density aquaculture systems with the same biofilm carriers.The feed coefficients were reduced by 0.20,0.13 and 0.21,respectively.The high density aquaculture systems will reduce the growth rate,survival rate and food utilization rate of the shrimp.When the stocking density reaches the upper limit of the nitrification capacity of the aquaculture systems,high density aquaculture systems will not increase the production of per unit water body,which will increase the cost of aquaculture.