The application of sponge iron (SI) carriers can improve the biochemical treatment performance of sequencing batch reactors (SBR) during wastewater treatment. This study used SBR reactors to explore the effects of SI dosage on the nitrogen removal performance and reactor stability and microbial community structure under low temperature and ultra-low load. In contrast to conventional SBR, the average removal rate of total nitrogen (TN) in the biological sponge iron system (BSIS) was increased by 5.38 % for 45 g/L, 18.93 % for 90 g/L, and 13.52 % for 135 g/L, respectively. The nitrogen removal performance and reactor stability showed the best performance under the SI dosage of 90 g/L. The addition of SI formed the anaerobic-anoxic-aerobic microenvironments, which facilitate the propagation of denitrifying bacteria (Saccharimonadales, Hydrogenophaga) and iron bacteria (Rhodoferax and Acinetobacter) in the BSIS. This study provides a new insight on the application of SI in the wastewater treatment.

Strain QHR-5, a heterotrophic nitrification-aerobic denitrification bacterium (HNADB) with iron oxidation function, was isolated from biological sponge iron system (BSIS) and identified as Achromobacter denitrificans. The carbon source suitable for growth and nitrogen removal by the strain from the denitrification medium 1 (DM1) was investigated. Maximum growth and total inorganic nitrogen (TIN) removal were observed when Seignette salt was the carbon source. Single-factor experiments showed that the highest NO3- -N removal performance was achieved when C/N ratio was 17, the shaking speed was 120 rpm, the temperature was 30 celcius, and the pH was 7.0. The heterotrophic nitrification and aerobic denitrification activity with different nitrogen sources (NH4+-N, NO3- -N, and NO2- -N) showed removal efficiencies of 90.84%, 98.37%, and 60.37%, respectively. With NH4+-N, NO3- -N or NH4+-N, NO2- -N as mixed nitrogen sources, Strain QHR-5 still showed good denitrification activity. Runs R1 (BSIS) and R2 (BSIS + Strain QHR-5) showed that with higher concentration NO3- -N (981.12 mg/L), the TN removal efficiency of R2 increased by 18.32%. Higher TN removal efficiency could be attributed to the aerobic denitrification capability of Strain QHR-5 and the accelerated dissolution of Fe2+ in BSIS due to the iron oxidation function of Strain QHR-5.

许多研究致力于用生物脱氮技术去除污染水体中的氮.微生物固定化是采用物理或化学的方法,将微生物截留在某一特定区域的技术.该技术既可保证功能微生物在适宜条件下快速增殖,使其具有较高的抵御外界不利环境因素的优势,同时可提高功能微生物与本土微生物的竞争力.生物脱氮技术与微生物固定化技术相结合具有很大的应用潜力.综述了几种传统微生物固定化方法和新型微生物固定化方法的分类、原理、优缺点、应用范围及前景.在此基础上,以凝胶包埋法为例,介绍了微生物固定化技术强化生物脱氮的机理,如为微生物提供相应保护,加快微生物生长富集速度,在凝胶球内外形成不同浓度的溶解氧,以及额外提供功能微生物和营养物质等.以凝胶包埋法加快厌氧氨氧化菌生长富集速度,利用凝胶球内外溶解氧浓度差实现短程硝化-厌氧氨氧化为实例进行阐述.最后对微生物固定化技术强化生物脱氮目前存在的问题进行总结并提出展望,开发成本低廉且稳定性强的固定化材料具有重要意义.

对海绵铁的功能及在水处理中的应用进行了概述.分析了海绵铁脱氮和除磷的机理,并对影响海绵铁脱氮和除磷的因素(海绵铁投加量、pH、DO、温度)进行了阐述.总结了海绵铁在脱氮和除磷中的应用(人工湿地、生物膜法、厌氧氨氧化、生物海绵铁体系),对未来海绵铁与脱氮除磷的相关研究方向进行了展望.

零价铁(ZVI)作为一种活性金属,因其高效、无毒、价廉和来源丰富而被广泛用于硝酸盐(NO3–)的还原.尽管ZVI对硝酸盐有较高的去除效率,但传统ZVI法还原NO3–的主要产物是NH4+,其会对水体造成二次污染.此外,反应过程中形成的铁氧化物会抑制电子传递,从而使ZVI难以长时间维持高反应活性,对pH有较高的依赖.目前乃至今后的重点研究方向是开发或改善现有ZVI复合材料、耦合微生物工艺等手段以降低pH对反应的限制及还原产物中NH4+的比例,同时将其脱氮性能进一步优化提升.该文介绍了ZVI对NO3–的作用效能和去除机制,阐述了理化特性、pH、温度、溶解氧等因素对ZVI化学反硝化效能的影响,涵盖了ZVI还原硝酸盐的各项性能强化措施.最后归纳了ZVI材料在实际脱氮中需要注意的问题,对其未来发展前景进行了展望.

As a newly identified nitrogen loss pathway, the nitrate-dependent ferrous oxidation (NDFO) process is emerging as a research hotspot in the field of low carbon to nitrogen ratio (C/N) wastewater treatment. This review article provides an overview of the NDFO process and summarizes the functional microorganisms associated with NDFO from different perspectives. The potential mechanisms by which external factors such as influent pH, influent Fe(II)/N (mol), organic carbon, and chelating agents affect NDFO performance are also thoroughly discussed. As the electron-transfer mechanism of the NDFO process is still largely unknown, the extensive chemical Fe(II)-oxidizing nitrite-reducing pathway (NDFOchem) of the NDFO process is described here, and the potential enzymatic electron transfer mechanisms involved are summarized. On this basis, a three-stage electron transfer pathway applicable to low C/N wastewater is proposed. Furthermore, the impact of Fe(III) mineral products on the NDFO process is revisited, and existing crusting prevention strategies are summarized. Finally, future challenges facing the NDFO process and new research directions are discussed, with the aim of further promoting the development and application of the NDFO process in the field of nitrogen removal.

Sponge iron (SI) can serve as an indirect electron donor to provide Fe(II) for the nitrate-dependent ferrous oxidation (NDFO) process, producing OH- and magnetite. The SI-NDFO system mainly uses Fe(OH)(2) as an electron donor, achieving a TN reduction rate of 0.42 mg-TN/(gVSS.h) for a period of at least 90 days. The enrichment of iron-oxidizing bacteria and the competition of iron-carbon micro-electrolysis for reaction sites on the surface of SI are the main reasons for the improvement of total nitrogen removal efficiency (TNRE). With an influent NO3--N concentration of 50 mg/L and a SI concentration of 50 g/L (at pH 5.0 and 30 degrees C), the TNRE reached a maximum level of 38.28%. In addition, reducing the pH environment was found to improve the denitrification efficiency of the SI-NDFO system, although denitrification stability was also reduced as a result. Overall, the SI-mediated NDFO process is a promising technique.

反硝化是一种经济有效的废水脱氮技术.但由于其常需要外加碳源作为电子供体而导致了成本高和二次污染的问题.寻找新型的电子供体解决上述问题已经成为当前的研究热点.一般来讲,铁型反硝化技术是以还原态的零价铁和二价铁作为电子供体,污染物为电子受体进行脱氮.由于铁作为电子供体更易获取且成本低,更适用于低C/N比废水处理.本文对零价铁和二价铁介导的两种反硝化过程的脱氮机理,以及目前铁型反硝化的应用状况进行阐述.旨在推进实验室对铁型反硝化生物技术的深入研究,以及在水处理领域的应用.