不同分子量聚乳酸的异养反硝化脱氮性能及脱氮反应机制

聚乳酸(PLA)是一种发展潜力巨大的反硝化固体碳源。为探究不同分子量PLA反硝化脱氮路径及机制，以不同分子量PLA为固体碳源研究了PLA的静态释碳性能和反硝化脱氮效果，考察了反硝化出水溶解性有机质(DOM)组分和微生物群落结构。结果表明：PLA释碳稳定，在清水和脱氮反应器中出水COD均能稳定在20 mg·L⁻¹；PLA分子量越低，脱氮效果越好，5 000 g·mol⁻¹分子量PLA的NO₃⁻-N去除率和反硝化速率达到100%和1.29 mg·L⁻¹·h⁻¹。PLA脱氮路径有2条：一是反硝化功能菌群利用水解微生物分解PLA释放的小分子碳源作为电子供体进行异养反硝化作用；一是微生物利用溶解性微生物代谢产物等有机物进行反硝化脱氮。该研究结果可为PLA固体碳源在反硝化脱氮工艺中的高效应用提供参考。

Heterotrophic denitrification and denitrification mechanism of polylactic acid with different molecular weight

Polylactic acid (PLA) is a kind of denitrification solid carbon source with great potential. In order to explore the denitrification pathway and mechanism of PLA with different molecular weights, the static carbon release performance and denitrification efficiency of PLA with different molecular weights were studied, and the effluent of dissolved organic matter (DOM) components and the microbial community structure were analyzed. The results showed that PLA carbon release performance was stable, and the effluent COD concentration in both deionized water and nitrogen removal reactors could be stabilized at 20 mg·L−1. The lower the molecular weight of PLA was, the better the nitrogen removal efficiency was. The NO3−-N removal rate and denitrification rate of 5 000 g·mol−1 molecular weight PLA reached 100% and 1.29 mg·L−1·h−1. There were two pathway for PLA denitrification, one was that denitrifying bacteria used the small molecule weight carbon source released by hydrolyzed microorganisms PLA as electron donor for heterotrophic denitrification,the other one was that microorganisms used organic matter such as dissolved microbial metabolites for denitrification. The research results can provide a theoretical basis for the efficient application of PLA as solid carbon source in denitrification process.