| Recycling aquaculture has the advantages of saving water and little harm to environmental pollution for traditional aquaculture,but there are still some deficiencies in its technology and practical application.The economic and environmental benefits are seriously affected by the problems of more water treatment plants,longer process and less application of denitrification plants.As a new farming model,the bio-flocculation technology has the effect of highly efficient nitrogen and phosphorus removal,which can maintain the stability of the water quality of farming,and the flocs formed can be consumed by breeding animals,thus reducing the feed coefficient.Microbial suspension growth bio-filter is a water treatment unit of circulating aquaculture system,which makes full use of the advantages of flocculation technology.The nitrogen transformation of functional units in the circulating aquaculture system of suspension growth bio-filter was studied.The removal rate of tristate nitrogen in the reaction area and settling area of the microbial suspension growth biological filter and the nitrogen and phosphorus budget and cost structure of the circulating aquaculture system of the microbial suspension growth biological filter are expected to provide theoretical support and technical guidance for the application of the system in practical production.1.Nitrogen transformation in circulating aquaculture system of microbial suspension growth biological filterTaking the circulating aquaculture system of microbial suspension growth bio-filter as the research object,the conversion paths of tristate nitrogen in reaction area,settling area and cultivation area were studied respectively.In order to understand the system internal nitrogen conversion,better for the system application in aquaculture production as a guide.The results showed that the reaction area had a significant effect on the removal of nitrate nitrogen,while ammonia nitrogen and nitrite nitrogen had a transient accumulation.When the content of nitrite is high,the reaction area can remove it quickly and there is no obvious accumulation of nitrate.At this time,the reaction area is mainly for denitrification.The reaction zone can quickly remove the high concentration of ammonia nitrogen without the accumulation of nitrite and nitrate.At this time,the main occurrence is the assimilation of bacteria;A small amount of ammonia nitrogen and nitrite nitrogen can be treated in the settling area,and a small amount of nitrate nitrogen can be accumulated at the same time.However,when the concentration of nitrate is high,a small amount of nitrate nitrogen can be removed and there is no accumulation of ammonia nitrogen and nitrite nitrogen.Therefore,in the existing conditions,the settling area can be converted into ammonia and nitrite by nitrification,and denitrification can occur when the concentration of nitrate is high.The aquaculture area has an obvious ability to deal with ammonia nitrogen,and can deal with a small amount of nitrite nitrogen and the accumulation of nitrate nitrogen at the same time.It has no removal effect on nitrate nitrogen,and nitrogen transformation is mainly carried out through the path of nitrification.2.Study on the rapid transformation of tristate nitrogen by microbial suspension growth bio-filterAn experiment on the conversion of nitrate,nitrite and ammonia in the reaction area and settling area of microbial suspension growth bio-filter was carried out to explore the removal ability of microbial suspension growth bio-filter for nitrate,nitrite and ammonia.The results show that the reaction zone can remove a certain amount of nitrate by denitrification.During the removal process,there will be a short term accumulation of nitrite and the highest accumulation value will increase with the initial concentration of nitrate,the settling area has no obvious effect on nitrate removal.The removal time of nitrite increased with the initial concentration of nitrite in the reaction area,and a small amount of nitrate accumulated at the end of the reaction.The removal of nitrite in the settling zone has a certain removal capacity of nitrite,but it is relatively low;the conversion of ammonia in the reaction zone was rapid and thoroughly,there is a small amount of nitrate accumulation,the settling area has a weak ability to removal ammonia,and has nitrite and nitrate accumulation.The maximum removal rates of nitrate,nitrite and ammonia in the reaction area were 1.97 mg·?L·h?-1,0.76 mg·?L·h?-1and 8.10 mg·?L·h?-1,respectively.The maximum removal rates of nitrate,nitrite and ammonia in settling area were significantly lower than the reaction area,which were1.61 mg·?L·h?-1,0.29 mg·?L·h?-1 and 1.16 mg·?L·h?-1,respectively.3.Nitrogen and phosphorus budget and cost structure of circulating aquaculture system with microbial suspension growth biological filterThe nitrogen and phosphorus contents in the input and output items of the circulating aquaculture system of the suspension growth biological filter were quantitatively analyzed,in which the input included flocs,fish,water and feed,and the output included flocs,water,fish and others.The results of the 3-month experiment on the Australian precious bass showed that the feed accounted for the largest proportion of nitrogen and phosphorus input,92.87%and 91.36%,respectively,The nitrogen removed by denitrification was 36.72%.The maximum phosphorus output was flocs,accounting for 51.49%.Secondly,the phosphorus output of fish accounted for 32.57%.The absolute utilization rate of nitrogen,relative utilization rate of phosphorus and relative utilization rate of phosphorus were 33.70%,36.29%,27.22%and 29.80%respectively.The density increased from 5.75 kg·m-3 to 15.82 kg·m-3,the average weight increased from 32.56g to 167.09g,and the feed coefficient was 1.58.The water and electricity consumption per unit yield were 0.12 m3·kg-1 and 41.03 KW·h·kg-1,and the feed and sugar consumption per unit yield were 1.08 kg·kg-1 and 0.59 kg·kg-1,respectively. |
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