Experimental Study Of Nitrogen And Phosphorus Removal From Simulated Biogas Slurry Of Swine Farm By Airlift Loop Reactor

High concentrations of nitrogen and phosphorus is one of the main causes of eutrophication,while they all belong to essential and non-renewable resources.As biogas slurry still contains large amounts of nitrogen and phosphorus,so it would cause enormous harm to water if not solving efficiently.Recycling nitrogen and phosphorus from biogas slurry with the struvite crystallization method,not only it can remove nitrogen and phosphorus efficiently and provide a favorable base for subsequent biological treatment,but also accomplish the goal of recycling nitrogen and phosphorus and it is conducive to sustainable development of the resource of nitrogen and phosphorus.Current research on the recycling of nitrogen and phosphorus are mostly based on the research about the crystallization conditions of static beaker test,while in the study on mass production of crystallization reactor it is blank.This research designed a Airlift Loop Reactor autonomously for continuous-flow test,making sure the crucial and appropriate date for dealing with biogas slurry and the recovery potential and quality in order to provide a basis for further optimizing the reactor structure and scaling up test.This research used simulated biogas slurry as original water,then it performed continuous pneumatic experiment In loop reactor.The experiment considered the recovery efficiency of nitrogen and phosphorus as the index of evaluation to research systematically the process conditions of the struvite crystallization method and the factor affecting the struvite precipitation method,also optimizing process parameter and assessing removal efficiency of nitrogen and phosphorus was in order to provide theoretical foundation for following experiment.Main content and conclusions as follows:(1)Single factors effect analysis showed that pH value had an enormous effect on the recovery efficiency of nitrogen and phosphorus,and the best pH value is 10;best Mg/P Molar Ratio is 1.5,while additional magnesium increased almost had no special effect on the recovery efficiency of nitrogen and phosphorus;When N/P Molar Ratio is 1,the ammonia-nitrogen recovery efficiency could achieve highest,but phosphorus recovery efficiency was only above 75.1%;When the time lasted for 60 min,phosphorus recovery efficiency could achieve highest,and time lasted for 50 min,ammonia-nitrogen recovery efficiency could achieve highest.(2)According to the result of experiment it could obtain the optimal process conditions when pH=9.95,Mg:P=1.5,HRT=50min,the expected ammonia-nitrogen recovery efficiency is about 4.6%,and the phosphorus recovery efficiency is about 96.9%.The real dates indicated ammonia-nitrogen recovery efficiency is about 4.5%,and the phosphorus recovery efficiency is about 96.6% in the optimal process conditions.There is little difference compared with expected dates.(3)Increasing crystallization could induce reactions proceeding,and nitrogen and phosphorus recovery efficiency could have a corresponding increase.(4)Original concentration of the ammonia-nitrogen had little influence on nitrogen and phosphorus recovery efficiency,ammonia-nitrogen recovery efficiency is main about 54% while the phosphorus recovery efficiency is about 70%.(5)When continuous time of reaction made system keep at a steady state,the nitrogen and phosphorus recovery efficiency remained stable.Ammonia-nitrogen recovery efficiency is about 6%,and the phosphorus recovery efficiency is about 96.5%.(6)Analyzing the crystalline products by x-ray diffraction,SEM and EDS,we could learn that crystallization contain struvite crystals.