[Analysis of High-efficiency Denitrifying Bacteria and Embedding Filler Performance and Microflora]

In order to study adaptability and recovery capability of high-efficiency denitrifying bacteria and their embedding filler to low temperature and low substrate concentration, a test was performed under two conditions (favorable and unfavorable) and three stages (D₁, D₂, and D₃) to explore the denitrifying capability of the bacteria. The favorable condition was a reacting temperature of 30℃, a nitrate concentration of 300 mg·L^-1, and a C/N ratio of 10; and the unfavorable condition was a reacting temperature of 4℃, a nitrate concentration of 30 mg·L^-1, and a C/N ratio of 5. In stage D₁, high-efficiency denitrifying bacteria [300 mg·(L·h)^-1], which were cultured at favorable condition, were placed under the unfavorable condition. In stage D₂, the bacteria were embedded after the denitrifying performance was stable, and then this embedded filler was placed under the unfavorable condition and recovered in the favorable condition (D₃) after 90 days. The results show that the denitrification rates of stages D₁ and D₂ finally stabilized at 5.4 mg·(L·h)^-1 and 4.8 mg·(L·h)^-1, respectively, after operation for 17 d and 16 d, indicating that the bacteria and their embedding filler adapted to the unfavorable conditions of low temperature and low substrate concentration. In stage D₃, the denitrifying rate of the filler reached 300 mg·(L·h)^-1 after operation for only 12 d, indicating that the filler had rapid self-recovery capability. Scanning electron microscopy (SEM) was utilized to analyze the internal and external structures of the embedding filler and it was determined that both the internal and external structures were favorable for bacterial growth metabolism and mass transfer. The high-throughput sequencing analysis results show that the dominant genera in stage D₂ were still Pseudomonas, Thauera, and Gelidibacter, which have denitrifying functions, thereby indicating adaptability of the bacteria under the unfavorable condition. The dominant genera Thauera, Petrimonas, and Pseudomonas of the embedding filler in stage D₃ were identical to the dominant genera of the high-efficiency denitrifying bacteria cultured under the initial favorable condition, which also showed that the bacteria embedding filler had good recovery capability.