Studies On Short-Cut Biodenitrification By Immobilized Microbe

Biodenitrification is one of important techniques in environmental engineering.The short-cut biodenitrification is that NH4+-N is oxidited into NO2- and then is reduced directly into N2,the process needs nitrite bacteria and denitrification bacteria. In this paper, adopted augmenting culture in nitrite bacteria culture media and the method of silica gel plate isolation,31 strains of bacteria were isolated from vegetable garden soil of our school. The color reaction test was carried out with Griess reagent and culture fluid, which was regarded as the index to determine producing NO2- or not. 13 strains which color were deep were obtained and they were further rescreened by doing nitrite test. A strain N4(coded N4,the same to the following)with higher rate of nitrosification was picked up after rescreened; A strain B08( coded B08 ,the same to the following) with higher rate of denitrification was obtained after isolated and rejuvenated from our lab conserving mixed denitrifying bacteria culture. Then made them into immobilized cells respectively using polyvinyl alcohol and sodium alginate as carrier.The experiments werecarried out for the selection of nitrosification and denitrification conditions. The results were as follows. At the temperature of 25~30C,initial pH value of 7.5~8.0,alkalinity of NaHCO3 concentration 1700mg/L, NH4+-N concentration of 150mg/L,aerations of 110rpm, cultured 24h,immobilized nitrite bacteria N4's NH4+-N removal efficiency reached 99.47%,accumulative volume of NO2--N was 116.65mg/L.Under the condition of temperature 25~30C,initial pH value 7.0~8.0, NO2--N concentration 200mg/L,C/N ratio 1.4,anareob and using acetate sodium as carbon source and electron donor, 8h the NO2--N removal rate of immobilized denitrifying bacteria B08 was 86.37%. In addition, under the above-selected nitrosification condition, the immobilized cells N4 and B08 were used for the combined short-cut biodenitriflcation with the ratio of immobilized cells 1:1 and the seed volume 15%(W/V), 27h the denitrogenation efficiency reached 97.53%; the immobilized cells N4 and B08 were used to do denitrogenation application test on eutrophic lake water of our school, 12h the NH4+-N removal rate was 84.06%.