Nitrogen Removal Of Ammonia Wastewater By Immobilized Ammonia-Oxidizing Bacteria With Aerobic Denitrifying Bacteria And Its Biofilm Observation

Traditional biological nitrogen removal is composed of aerobic nitrification and anaerobic denitrfication.Because of the complicate operation and the high cost of traditional way,several new biological processes have been developed,such as anaerobic ammonium oxidation (Anammox),Single reactor system for High Ammonia Removal Over Nitrite process(SHARON),completely autotrophic nitrogen removal over ntrite process(Canon)and oxygen-limited autotrophic nitrification denitrification process(Oland).The experimental design of the process applied in this paper is to accumulate nitrite by ammonia-oxidizing bacteria(AOB),then transfer the nitrite to nitrogen by aerobic denitrifying bacteria immediately.Compared to the traditional nitrification and denitrfication process,25%oxygen consumption would be saved through partial way.It also simplified the technology avoiding aeration during the process of SHARON beacause the bacteria we used were both aerobic(or part).One ammonia-oxidizing strain was isolated.The 2^ndAOB has a high similarity with Ochrobactrum anthropi after morphological,biochemical identification and Biolog system analysise,and it was named as Ochrobactrum sp.CZ.The medium component and incubate conditions of this strain was as following:(NH)4))2SO)40.71g,NaAC 4.4 g,NaCl 3.0 g,FeSO₄ 0.03 g,Fe₂(SO₄)₃0.03g,K₂HPO₄ 1.0 g,MgSO₄0.03 g,CaCl₂ 0.5 g,H₂O 1000ml;pH=8.5,incubate temperature 28-30℃,20%of liquid volume,rotating speed 120 r/min.After incubated under the optimal conditions,the number of bacteria increased obviously with regard to the original condition.The ammonia degradation ratio also increased from 70%to 90%.The aerobic denitrifying bacteria FX preserved in the lab was identifyed.It showed 85%of similarity with Alcaligenes faecalis and named as Alcaligenes sp.CZ.This strain could remove 200 mg/L of initial nitrate with 8mg/L of dissolved oxygen in broth.However,the denitrification ability of Alcaligenes sp.CZ would be prohibited to some degree when the nitrate came up to 550mg/L.Calcium alginate(CA)gel beads and polyurethane foam(PUF)were used to compare the ability in nitrogen removal between planktoinc cells and immobilized cells.Bacteria embedded in CA beads showed the highest activity,23 mg/L of initial ammonium nitrogen could be removed in 24 h in aerobic circumstance.Bacteria attached on the CA bead also showed good ability to remove nitrogen.We also studied and observed the biofilm of the two strains under fluorescence microscopy after being dyed by a kind of nucleic acid dyestuff.Biofilm on CA bead under different concentration of NaCl was evaluated.The result showed that the number and structure of biofilm have correlation with the ammonia removal ability of bacteria to some degree.