Based on traditional microbiological methods, a novel denitrifier Pseudomonas sp. N3 with excellent denitrification capacity at low temperature was isolated and identified using phenotypic and phylogenetic analysis. Complete nitrate removal was achieved at C/N=8, that is, 70 mg·L-1 nitrate. In addition, the isolate exhibited a great adaptability for low temperature and can reach 100% removal of 15 mg·L-1 nitrate at a temperature as low as 4℃ within 36 h. The denitrification genes of narG and nirS were highly expressed; they were at the same order of magnitude as those at 30℃. Semicontinuous experiments were conducted to test the stability of N3 immobilized with polyvinyl alcohol and sodium alginate at 10℃. The results show that immobilized N3 can remove 15 mg·L-1 nitrate completely within three days and maintains a strong mechanical performance and stability during the whole 54 days. The cold resistance and high denitrification ability of the strain N3 make it applicable to nitrogen wastewater treatment in winter.
Keywords: denitrifier; immobilization; low C/N; low temperature; semicontinuous experiment.