Research On Optimization And Application Of Nitrogen And Phosphorus Concentration And Electrochemical Recovery Process In Livestock And Poultry Wastewate

With the increasing scale of poultry breeding industry,the environmental pollution it brings is also increasing.Because the content of nitrogen and phosphorus in chicken manure biogas slurry is much higher than other biogas slurry,the recyclable value is higher,so how to efficiently recover nitrogen and phosphorus from chicken manure biogas slurry has become the focus of the industry.This project takes anaerobic fermentation of raw chicken manure as the starting point,explores a combination process of"ultrafiltration+concentration+electrochemical MAP",and explores the possibility of practical application of this combination process through the research method of"small trial+pilot trial",and provides a guiding scheme for the resource utilization of chicken manure biogas slurry.1)The whole process of autonomous anaerobic fermentation of chicken manure biogas slurry was tested in this subject.By adding fresh chicken manure raw materials daily and controlling the constant temperature of anaerobic fermentation system,the final gas production rate of the system was stable at about 90 L/h;The content of CH₄ in gas production is maintained at about 70%.The anaerobic fermentation process is stable and the properties of biogas slurry are stable.2)In view of the characteristics of high concentration of solid suspended solids in chicken manure biogas slurry,this topic adopts ultrafiltration process to remove solid suspended solids.By comparing the filtration effect of three ultrafiltration membranes,it is found that ceramic membrane has the best filtration effect,and the content of solid suspended solids in biogas slurry after ultrafiltration is only 11.7%of the initial content,creating favorable conditions for the subsequent process.3)In view of the large volume and low salt content of chicken manure biogas slurry,this topic first applies the electrodialysis process to concentrate the biogas slurry,the final concentration of ammonia nitrogen and phosphate in the biogas slurry in the concentration chamber are 7 times and 5.4 times of the initial concentration,but the biogas slurry in the electrodialysis light chamber still contains part of nitrogen and phosphorus,in order to solve this problem,the application of DTRO process for the second concentration of biogas slurry in the light chamber.The concentration of COD in the concentrated water is 9.9 times of the initial concentration.The concentration of nitrogen is about 7 times.The concentration ratio of phosphorus is about 12 times.After testing,it is found that all the indexes of the produced water are lower than the water quality standard of farmland irrigation.The combined process of"electrodialysis+DTRO"was used to concentrate 1925 L biogas slurry,and finally obtained488.8 L of concentrated water,which reduced the volume of biogas slurry by about 75%,enriched the nutrients in the biogas slurry,and improved the treatment efficiency of the subsequent electrochemical MAP process.4)In view of the inefficiency and instability of the application of traditional MAP process to recover nitrogen and phosphorus,the combined process of"electrochemical+MAP"is adopted in this project.Under the strengthening of electric field force,NH₄⁺and PO₄^2-in biogas slurry are combined to form struvite crystals when they meet Mg²⁺released by magnesium anode and precipitate from the biogas slurry,effectively recovering nitrogen and phosphorus in the biogas slurry.The extracted struvite can be used as slow-release fertilizer for crop planting,which produces good economic benefits and realizes the resource utilization of biogas slurry.First of all,the concentration of ammonia nitrogen after concentration of biogas slurry is relatively high.In view of this characteristic,about 93%ammonia nitrogen is removed by alkali addition and aeration blowing method at a pH of 10.7.Then,the process conditions of electrochemical MAP were optimized through a small test.It was found that 75.15%of ammonia nitrogen and 93.55%of phosphate could be recovered after 105 min reaction under the conditions of pH value 9.0 and current density 20 m A·cm^-2.After XRD analysis and electron microscopy observation,the composition of the product can be determined to be mainly struvite.Finally,the pilot test verified that under the above conditions,72.9%ammonia nitrogen and93.48%phosphate were recovered from the biogas slurry of chicken manure.The pilot test results were consistent with those predicted by the pilot test.The obtained precipitate was found to be mainly composed of struvite with high purity after XRD characterization and electron microscope observation.Through the calculation of the process cost and analysis of economic benefits,the process can meet the needs of chicken farm biogas slurry treatment,and produce certain economic benefits.In summary,the combined process of"ultrafiltration+concentration+electrochemical MAP"in this study can realize the resource utilization of chicken manure biogas slurry,and the feasibility of application in practical production is high,providing technical guidance for the resource treatment of chicken manure biogas slurry.