近年来的研究表明游离亚硝酸(FNA)是影响聚磷菌除磷活性的真正抑制物质，然而FNA抑制PAO除磷活性的机理还不清楚，如何避免FNA的积累、维持EBPR工艺的稳定性尚无切实可行的方法。多聚磷酸盐(poly-P)的代谢(包括合成与分解)是EBPR的关键步骤，而催化上述代谢反应的关键酶分别为聚磷酸盐激酶1和聚磷酸盐水解酶，但是FNA如何影响poly-P的代谢过程尚未见文献报道。本项目目的是深入研究FNA对PAO聚磷酸盐激酶1、聚磷酸盐水解酶活性和ppk1、ppx基因表达水平的影响，同时系统研究硝化微生物的种群结构及其与FNA积累和EBPR工艺稳定性的关系，探索利用高效亚硝酸氧化细菌解除FNA积累、恢复系统除磷功能的作用与潜力。本项目研究结果对于阐明FNA抑制生物除磷的机理，实现EBPR工艺的稳定运行具有十分重要的理论与实践意义。

Current studies have demonstrated that free nitrous acid (FNA) represents the true inhibitor affecting PAO’s activity. However, the mechanisms involved in this inhibition have not been elucidated and applicable measures are still unavailable for avoiding FNA accumulation and maintaining the process stability. Synthesis and hydrolysis of poly-P are the key steps responsible for EBPR. It is well known that.polyphosphate kinase 1 and exopolyphosphatase are responsible for catalyzing the synthesis and hydrolysis of poly-P, respectively in PAO cells. How FNA influences PAO's metabolism is still unclear. Therefore the objectives of the present project are 1) to systematically investigate the effects of FNA on the activity of polyphosphate kinase 1 & exopolyphosphatase and their gene expressions (ppk1 & ppx); 2) to investigate the community structure of nitrifying bacteria (i.e. ammonia-oxidizing bacteria and nitrite-oxidizing bacteria) and elucidate its roles in FNA Acculmulation and EBPR process stability; and 3) to explore the feasibility of preventing FNA accumulation and eliminating its inhibitory effects through introducing nitrite-oxidizing bacteria. Outcome from the present project will not only disclose the mechanisms involved in the inhibitory effects caused by FNA, but also lay a solid foundation for maintaining EBPR process stability.