Research On Optimal Design And Application Of Fish Culture Wastewater Treatment Process

The fish farming industry plays an important role in our country’s agricultural development.The continuous expansion of farming scale brings good economic benefits.However,due to the increase in the degree of intensification,the unauthorized discharge of farming wastewater causes the deterioration of the ecological environment.Reducing the environmental pollution caused by farming wastewater,and achieving a balance between fish farming and the ecological environment,how to achieve effective treatment of farming wastewater is currently the main problem.At present,the fish farming wastewater treatment technology is not mature enough,and there is not enough technical research to support it in actual projects.In this paper,through a full analysis of the water quality characteristics of fish farming wastewater,based on the absorption of traditional biological filter technology and biological contact oxidation technology,a solid-liquid separator,fiber bundle,ceramsite,and zeolite filter are integrated into one.New combined sewage treatment process.According to the characteristics of aquaculture wastewater,the process is optimized in structure to achieve layer-by-layer filtration and step-by-step purification of pollutants,to achieve"three-level filtration+three-level removal"of wastewater,and explore the treatment effect of this process on fish farming wastewater and Contaminant removal mechanism within the process.By improving and supplementing traditional biological filters,we hope to provide new ideas for the development of low-consumption and high-efficiency wastewater treatment processes for large-scale pond fish farming,and broaden the path for research on the use of ecological measures to treat farming wastewater.This thesis has achieved the main research results:1.Process optimization design:On the basis of absorbing the advantages and disadvantages of the traditional aerated biological filter,a new aerated biological filter combination process combining solid-liquid separator,fiber bundle,ceramsite and zeolite biological filter is designed.The design of the biological filter reactor has an inlet flow rate of 2m³/d,a single filter size S×H=1.05m×1.4m,and a single filter material volume of 0.9m³.The combined process is divided into 6 parts.The water inlet area,solid-liquid separation area,level 1 biological filter,level 2 biological filter,level 3 biological filter,and outlet area.Level 3 biological filter uses fiber bundle,ceramsite,and zeolite as a carrier filter.By optimizing the internal filler structure of the filter,water intake,aeration and backwashing methods,the pollutant removal capacity of the biological filter is improved,the backwash cycle is extended,and the"three-stage filtration+three-stage removal"of wastewater is realized.2.Film hanging start test:the method of manual inoculation,continuous water inlet and intermittent aeration is used to start the system film hanging.Under the conditions of temperature change of 20-28℃,DO≈3mg/L,and p H of 6.9-7.4,after 21 days of cultivation,the attachment of brown biofilm,NH₄⁺-N,COD_Mn can be observed on the surface of the filler and the inner wall of the test device The removal rate of TP is about 65%,55%,45%,and the water output of the system tends to be stable,and the system has completed the film hanging.The test proves that the method of inoculating activated sludge can effectively shorten the start-up time of the filter.3.Operation parameter optimization test:After the system has completed the film hanging,a single factor test is carried out on the main operation parameters of hydraulic retention time,gas-water ratio,and temperature to analyze the removal effect of pollutants under different working conditions.The test results show that when the gas-to-water ratio is12:1,the hydraulic retention time is 10h,and the temperature change is between 28-32℃,the biological filter has a good removal effect on each pollutant,and it is determined that this working condition is the combination Operating parameters of the process.4.Treatment efficiency test:The combined process is applied to the experimental study on the effect of treating fish farming wastewater.The results show that the system operates under optimized parameters and has a better treatment effect on fish farming wastewater.The rates were 74%,80%,40%,and 57%.Biological filters at all levels have different removal effects on different pollutants,filters at all levels are effectively used,fiber bundle filters have good removal effects on COD_Mn,NH₄⁺-N,TN,TP,and ceramsite filters The removal effect of COD_Mn and TP is better,and the removal effect of zeolite filter is better for NH₄⁺-N and TN.5.Study on the characteristics of microorganisms in the filter tank:the bacterial diversity in the biological filter tank is very rich,and the dominant bacteria are:Proteobacteria,Firmicutes,Planctomycetes,Bacteroidetes,Chlorobi.The dominant bacteria are:Roseovarius,Acinetobacter,Methanomassiliicoccus,Rhizobium,Clostridium sensu stricto.Biomass in the biofilter gradually decreases in the direction of water flow,and the microbial diversity and abundance gradually decrease,which is consistent with the gradual reduction in the removal rate of pollutants along the way.It is explained from the side that pollutant removal mainly occurs in the front filter.The microbial community structure is closely related to the operation of the system.At the stage when the pollutant removal effect is better,the microbial community structure in the biofilter is the most complex and rich in biodiversity.6.Research on the removal mechanism of pollutants in the filter:Based on the research results of the biological filter performance,filter material adsorption characteristics and microbial community structure,the removal method and mechanism of the biological filter for pollutants in fish culture wastewater are analyzed.Suspended matter in fish farming wastewater is mainly removed by suspended matter separator,fiber bundle filtration and filler adsorption;COD_Mn is mainly removed by mechanical interception,adsorption and microbial degradation;TN passes through a large number of nitrification and denitrification microorganisms in the biological filter Removal by decomposition;TP is mainly removed by decomposition and transformation of phosphorus accumulating bacteria,filler adsorption and chemical precipitation.There is a certain degree of dynamic response between changes in microbial community structure and changes in water quality,but changes in water quality are not entirely determined by microorganisms,and are also affected by many factors such as water temperature,dissolved oxygen,and p H.The study found that at a stage when the biological filter treatment effect is better,the microbial diversity and relative abundance in the system are at a relatively high level,indicating that the adjustment of the microbial community structure of the biological filter by adjusting different influencing factors can help the biological filter treatment efficiency Improvement.