不同碳氮比下污水反硝化过程中亚硝氮积累的特性研究

以乙酸钠为碳源,在不同的碳氮比(COD/NO_3~--N)条件下,通过控制反应器中反硝化时间,将NO_3~--N仅还原至NO_2~--N,实现NO_2~--N的稳定积累.结果表明,反硝化时间从60 min缩短至20 min,NO_3~--N还原速率和NO_2~--N积累速率分别增大至0.417 g·g~(-1)·h~(-1)(以VSS计,下同)和0.402g·g~(-1)·h~(-1).经过108 d的培养,NO_2~--N的积累率为95%.反硝化活性随碳氮比的增大而增大,而较低碳氮比更有利于NO_2~--N的稳定积累.在反硝化亚硝氮积累过程中,当碳源充足时,由于电子受体NO_3~--N和NO_2~--N相互竞争碳源,NO_3~--N的存在会抑制NO_2~--N的还原,从而导致NO_2~--N积累;而当碳源不足时,基质限制使NO_3~--N优先还原,导致NO_2~--N的积累.微生物宏基因组测序结果表明,培养污泥中的优势菌群为Thauera(71.85%),该菌仅能将NO_3~--N还原为NO_2~--N,从而导致NO_2~--N的积累.

Nitrite accumulation in denitrification with different C/N ratios

Nitrate reduction to nitrite for nitrite accumulation through controlling the reaction time in denitrification was investigated in a sequencing batch reactor (SBR) with sodium acetate as the electron donor under different C/N (COD/NO₃^--N) ratios. When the reaction time was reduced from 60 to 20 minutes nitrate reduction rate and nitrite accumulation rate respectively increased to 0.417 g·g^-1·h^-1 and 0.402 g·g^-1·h^-1. Nitrite accumulation rate could reach more than 95% after 108 days of cultivation. The denitrifier activity increases with the increase of C/N ratios. Low C/N ratios favor nitrite accumulation. When carbon source was sufficient, electron acceptor (nitrate and nitrite) competition and nitrate inhibition resulted in nitrite accumulation. However, nitrite accumulation occurred due to lack of substrate under carbon limitation. Results of Metagenomic sequencing analysis demonstrate that Thauera dominated in the microbial community of the culture, accounting for 71.85% of total population. This bacterium may play a major role in nitrate reduction to nitrite.