Anaerobic ammonium oxidation coupled to Fe(III) reduction: Discovery, mechanism and application prospects in wastewater treatment.

Fe(III) reduction coupled with anaerobic ammonium oxidation is known as Feammox. Feammox, which was first discovered in wetland ecosystems, has the potential to be used in wastewater treatment systems due to its ability to remove ammonium. Feammox can produce N2, NO2- or NO3- through the reduction of Fe(III) and oxidation of ammonium, which is a potential process to nitrogen loss from aquatic ecosystems and terrestrial ecosystems. The Acidimicrobiaceae sp. A6 was the first Feammox functional bacteria that was successfully isolated from wetlands. The nitrogen removal effect of Feammox can be influenced by many environmental factors, such as pH, organic matter, and different sources of Fe(III). Feammox has broad application prospects, but more exploration is needed to apply this principle to wastewater treatment. This review introduces the development, mechanism, functional microbes and factors affecting the Feammox process, and discusses its potential applications.

[Effect of Chelated Iron on Nitrogen Removal Efficiency and Microbial Community Structure in the Anaerobic Ferric Ammonium Oxidation].

In order to understand the characteristics and interactions of the microbial community during the anaerobic ferric ammonium oxidation (FEAMMOX) process, this study investigated the effects of various forms of chelated iron on nitrogen removal efficiency and microbial community structure. After 77 days of reactor operation, the removal efficiency of total nitrogen was 83.32% for the ferric humate group, 43.67% for the ferric citrate group, 55.07% for the ferric sodium ethylene diamine tetraacetate group, and 12.65% for the ferric ammonium triacetate group. After the experiment, the abundance of denitrifying bacteria Comamonadaceae in ferric humate group was 17.57%, the abundance of Clostridium in ferric citrate group was 47.70%; and the abundance of denitrifying bacteria Thermomonas in the ferric sodium ethylene diamine tetraacetate group was 20.11%. This indicates that ferric humate is a more effective electron acceptor for the FEAMMOX process. The result of function prediction shows that the iron, sulfur, and nitrogen cycles are all closely related, with iron and sulfur metabolism playing an important role in nitrogen removal. In the humate group, iron respiration and the nitrogen cycle are more strongly correlated than other groups. Co-occurrence network analysis showed that the keystone species in the FEAMMOX process is Tessaracoccus.