The Research On The Key Technology Of Utilization From Livestock Wastewater

There is currently a global shortage of nitrogen and phosphorus resources,especially phosphorus.Recent years,the treatment and utilization of livestock wastewater has attracted attention from all sectors of society.After anaerobic fermentation of livestock and poultry manure water,not only biogas,a large amount of biogas slurry and biogas residue are also produced.Among these,the COD and ammonia nitrogen load of chicken manure biogas slurry is several times that of biogas slurry such as pig manure,which results in the difficulty of improving chicken manure biogas slurry treatment.At present,the resource treatment and utilization of chicken manure biogas slurry are rare reports.The concentration process has become a key process for resource utilization and standard discharge.In order to reduce the volume of biogas slurry,enrich the nutrient content,facilitate transportation and reduce cost.The electrodialysis process as one of the concentration methods is widely concerned and applied,and the guano stone method is the most popular because of its phosphorus recovery and also removing nitrogen and phosphorus.In this study,using the biogas slurry of chicken manure as the research object,we combined a new efficient method of electrodialysis+electrochemistry+guano precipitation system to concentrate and remove nitrogen and phosphorus,which provided a guiding scheme for the resource utilization of biogas slurry of chicken manure and the recovery of nitrogen and phosphorus resources.Firstly,the electrodialysis process was used to concentrate chicken biogas slurry,a Box-Behnken experiment scheme was designed by Design-Expert,the effect of nitrogen and phosphorus concentration of circulating flow,voltage and pH were analyzed by response surface methodology.The results of experiment proved that when the circulating flow was 20～60 L/h,voltage was 10～18 V and pH was 6～8,ammonia nitrogen and phosphate concentration rate were affected by the three factors which was circulating flow>voltage>pH.The regression model equation was established,the best conditions were:A1SL membrane,circulating flow of 40 L/h,voltage of 14 V and pH of 8.Experimental verification results were 84.4%phosphate concentration rate,329.18%ammonia nitrogen concentration rate and the prediction value errors were 1.33%and 0.92%respectively.Secondly,using the electrochemical approach,the nitrogen and phosphorus nutrients from chicken manure marsh slurry were removed and droano was recycled.A Box-Behnken experiment scheme was designed by Design-Expert,the effect of nitrogen and phosphorus removal of the initial pH value,reaction time and current density were analyzed by the response surface method.The results showed that initial pH was the main factor of the electrochemical MAP reaction.The influence order of the three influencing factors on the phosphate removal rate was the initial pH value>reaction time>current density.The order of influence on ammonia nitrogen removal rate was initial pH value>current density>reaction time.The regression model equation was established,and the optimal process condition were initial pH value of 6.5,reaction time of 35 min,current density of 20 m A·cm^-2.Verification test results showed:phosphate removal rate was 96.9%,ammonia nitrogen concentration removal rate was33.4%,and the prediction result errors were 0.81%and 1.83%respectively.The precipitation obtained from the test was subjected to XRD analysis,and the characteristic peak was basically consistent with the standard magnesium ammonium phosphate precipitation characteristic peak indicating that the precipitation bird boulder content was high,but the biogas slurry composition was complex,and other impurity precipitations were generated.Finally,the pilot tests of the ultrafiltration and electrodialysis system were conducted.Polymagnetic,PVDF,and ceramic membranes were used respectively in the ultrafiltration tests.By comparing the changes of COD and other water quality index,ceramic membrane determined the best filter stability for biogas slurry before and after ultrafiltration.At the voltage of 120V,concentrated chamber,light chamber and pole chamber flow were 4,4,1.5 m³·h^-1 respectively.The biogas slurry was concentrated 5times using electrodialysis process.The phosphate concentration rate was 44.47%after the first concentration,and increased to 201.75%after 5 times.The concentration rate of ammonia nitrogen after the first concentration was 91.94%,and increased to 469.32%after 5 times,which was more consistent with the results of small test.