The Segregation And Immobilization Of Nitrifying Bacteria And Its Preliminary Application In Constructed Wetland

With the eutrophication being on the rise in our country,more and more people increasingly recognized the importance of environmental protection.Constructed Wetland as an effective treatment technology,is an efficient and environmental friendly sewage treatment.It also has ecological aesthetic effect.Research on wetland wastewater biological denitrification has become a hot topic in the field of environmental protection.In recent years,the bioaugmentation technique is widely used in water treatment,especially nitrogen wastewater treatment field,Constructed wetland microbial community structure be changed by manual technique,can increase the amount and type of microorganism and play a positive role to adjust the removal efficiency of the Constructed Wetland.This paper focused on screening of nitrifying bacteria which had the ability of nitrogen removal from the supeernatant of activated sludge and analyzing 16S rDNA.Use PEG and SA as mixed carrier materials to immobilize nitrifying bacteria,and conduct performance test,such as the effect of immobilization globule balling,mechanical strength,permeability and crushing rate.The range of the concentration of PEG,SA,cross-linking agent and cross-linking time were confirmed through some and ammonia degradation rate as test index to carry out orthogonal test.Nitrite bacteria,nitrifying bacteria and denitrifying bacteria were immobilized and their immobilized conditions were optimized.The degradation efficiency of three immobilized pellets were measured at different temperature,pH value,DO and immobilized pellets dosage.The optimize degradation condition were confirmed by the orthogonal test.Finally,immobilized bacteria was used in constructed wetlands by using two release method,and test nitrogen removal of two constructed wetlands.The results were as follows:(1)three nitrite bacteria and three nitrifying bacteria which had the ability of nitrogen removal were separated from the supernatant of activated sludge.The Y-1 and X3 strain that had the highest degradation rate.Degradation had excessed more than 20%in 48 hours.16S rDNA sequence confirmed that the Y1 belonged to Klebsiella pneumoniae;(2)The immobilized test of Y1 confirmed the optimum immobilization conditions:PEG at a concentration of 8.0%,SA at a concentration of 3.0%,CaCl2 at a concentration of 3%,cross-linking time is 20 hours.The concentration of the PEG had the largest influence on the degradation efficiency,followed by the concentration of the SA,CaCl2 and cross-linking time.Four factors above had no significant influence on the immobilized globule degradation efficiency.(3)To optimize degradation condition of the three bacterium immobilized particles,The results showed that the condition at 32?,pH value of 8.0,DO of lmg/L,the amount of immobilized particles 40g/L,the nitrite bacteria and nitrifying bacteria reached the maximum degradation efficiency.Among above conditions,temperature had the biggest influence in the degradation efficiency,followed by pH,the amount of immobilized and DO;However,denitrifying bacteria's maximum degrading conditions were temperature of 30?,pH value of 7.0,DO of 1.5mg/L.The amount of immobilized particles was 80g/L.Temperature was the biggest influence parameter,the following were DO as well as the amount of immobilized globule,and the value of the pH.Four factors for influence of the degradation efficiency showed insignificance.(4)Using two immobilized bacteria dosing method in the constructed wetlands,the results showed that compared with the comparison of constructed wetland,two constructed wetlands had a higher removal efficiency of NH4+-N,TN and COD,and system 1 had a higher ability of NH4+-N,TN and COD than the system 2.Therefore,system 1 had better effect.