Anaerobic ammonium oxidation coupled to iron reduction in constructed wetland mesocosms

Electrode Colonization by the Feammox Bacterium Acidimicrobiaceae sp. Strain A6

“…CWs were set up and operated with two different Fe levels in their sediments, to determine how Fe levels affected the removal of NH 4 + via Feammox after augmentation with A6. The CW with higher Fe levels had higher A6 counts and greater NH 4 + removal ( 43 ). For the purposes of this study and to establish well-controlled conditions to gain further insights into the electrogenesis of A6, electrode pairs were installed in the two CW mesocosms.…”

“…The substrate was then thoroughly mixed prior to loading into the mesocosm columns. The CWs were planted with Scirpus acutus (bulrush) and were operated in a growth chamber (Environmental Growth Chambers) simulating the summer climate of New Jersey (Table S5), as described previously ( 43 ).…”

“…Details of the CW mesocosm operation were given in a previous report ( 43 ). After 4 months of operation, when the mesocosm had become more reduced and plants were fully established, another A6 enrichment culture (around 10 7 A6 counts/ml of culture; 250 ml per CW mesocosm) was injected from the bottom into each CW on day 124, to ascertain the colonization of A6 in the mesocosms.…”

“…At the end of the experiment, the CW mesocosms were dismantled and soil samples were taken for analysis of microbial communities. Soil sampling was described previously ( 43 ). Electrodes installed in the CW mesocosms were removed carefully, and attached bacterial samples from the electrodes were obtained using the same procedure as described above (see Table S4B in the supplemental material for details).…”

Oxidation of ammonium by FeammoxAcidimicrobiaceaesp. A6 in anaerobic microbial electrolysis cells

“…2,3 To lower the energy consumption for wastewater treatment, anaerobic oxidization of NH Iron is abundant in the environment and thus Feammox can be enhanced in systems such as constructed wetlands to treat some wastewaters. 10 However, adding a stoichiometric amount of FeIJIII), shown in eqn (1), to wastewater treatment reactors to remove NH 4 + via the Feammox reaction is not practical because the large amount of iron oxides required results in the accumulation of iron phases over time in the reactor, which requires removal and disposal. To implement the Feammox process for large scale or long-term continuous-flow reactor applications, the requirement of having to add a solid FeIJIII) phase needs to be addressed, and an electrode is a suitable option as it can act as the electron acceptor substituting the need for FeIJIII) addition.…”