Anammox — Wikipédia

Anaerobic oxidation of ammonium

Bioreactor containing anammox bacteria Stuttgartiensis (Radboud University Nijmegen)

Lipids C17-C20 of the anammox bacteria type containing three crushed cyclobutane rings with a cyclohexane cycle or five consecutive cyclobutans. The corresponding fatty acids are esterified with methanol or on a glycerol skeleton while ladderanic alcohols are linked via an ether function with glycerol, all in different combinations.

Nitrogen biological cycle
(DNRA: dissimilatory nitrate reduction to ammonium )

L’ anaerobic oxidation of ammonium or the ” Anammox ^{[ note 1 ]} “Is an important metabolic microbial route of the nitrogen cycle during which the chemical energy of the nitrate no ₃ ^– _{et de l’ammonium NH4⁺ est utilisée par certaines bactéries pour fixer le dioxyde de carbone. Ces bactéries qui réalisent ce processus ont été identifiées en 1999 et ont constitué à l’époque une surprise pour la communauté scientifique. Ce type de réactions se déroule dans de nombreux milieux naturels. Une méthode d’élimination de l’ammonium développée par l’université de technologie de Delft est également commercialisée sous le nom d’anammox.}

In the biological process, the NH ammonium cation ₄ ⁺ _{est oxydé par l’anion nitrite NO2⁻ pour donner du diazote N2. Ce processus contribue à hauteur de 50 % de l’azote produit dans les océans. C’est donc un important puits d’azote qui limite ainsi la production primaire des océans. La réaction globale s’écrit :}

NH ₄ ⁺ _{+ NO2⁻ → N2 + 2 H2O.}

The bacteria that perform the anammox process belong to the bacterial phylum of the planctomycetes, whose best known genres are Planctomyces And Pirenlula . Currently, five kinds of anammox bacteria have been (temporarily) defined: Brocadia , Enjoy , Anammoxoglobus And Jettenia concerning the species of fresh water, as well as Scalindua Regarding marine species.

Anammox bacteria are characterized by several remarkable properties.

The anammox process was initially observed at temperatures between 20 °C And 43 °C ^{[ 4 ]} , but it has been observed more recently in hot sources at temperatures between 36 °C And 52 °C ^{[ 5 ]} and in hydrothermal sources located along the medio-Atlantic ridge at temperatures between 60 °C And 85 °C ^{[ 6 ]} .

The process Anammox Intervenes in the elimination of ammonium in wastewater treatment and consists of two separate processes. The first step is the partial nitrification (nitrosation) of half of the nitrite ammonium by bacteria such as Nitrosomonas :

4 NH ₄ ⁺ _{+ 3 O2 → 2 NH4⁺ + 2 NO2⁻ + 4 H⁺ + 2 H2O.}

Anammox bacteria can then convert NH ammonium ₄ ⁺ _{et le nitrite NO2⁻ en diazote N2 et environ 15 % de nitrate NO3⁻ :}

NH ₄ ⁺ _{+ NO2⁻ → N2 + 2 H2O.}

The two processes can take place in a single reactor where the two bacteria guilds form compact granules ^{[ 7 ]} .

The anammox process represents a promising alternative to conventional nitrogen elimination techniques used in treatment plants. It is for this reason that several patents using the properties of the anammox process have already been filed. Unlike the microbial flora present in the steps of biological treatment of a STEP, the bacteria of the genus Brocadia anammoxidans are able to dispense with oxygen and even consume carbon dioxide (greenhouse gas). The costly ventilation of basins can therefore be reduced, thereby reducing treatment costs and CO emissions ₂ up to 88%. The development of new processes is based on research work carried out in the 1990s, relating to microbiological activity during the nitrification/denitrification processes, and in particular on the mechanisms that lead to the availability of nitrogen. The work carried out in Vienna (Nowak und Svardal, 1993; Nowak, 1996), Delft (Van Niel et al., 1993; Van Loosdrecht und Jetten, 1998) and Hanover (Abeling, 1994; Hippen, 1999) deserve to be here to be cited. These discoveries have found their application in Rotterdam since the beginning of 2006. In Germany, the anammox processes have been applied in 2000 in different treatment plants, which is still limited to the treatment of part of the effluents (for example sludge liquor) . Until now, various systems have been available on the market for this particular application. In the years to come, the multiplication of experiences in life-size facilities will demonstrate to what extent the technical and economic requirements for the operation of a STEP are served. The application of the anammox process to all pre-treated waters has only been the subject of a single application in Austria, within the rhinestone treatment plant (Val de Ziller). Interest here also lies in reducing oxygenation needs and avoidance of CO emissions ₂ . The challenge to be met in this case is to bring together the ideal conditions for the growth of anammox bacteria (such as the temperatures of treated water, the age of sludge, etc.).

Nitrification/denitrification (steps transformation of ammonia into nitrites and then into nitrates then into atmospheric nitrogen through bacteriological activity in anoxic conditions) has long been considered the only source of liberation from the nitrogen of the air. The discovery of the oxidation of ammonium by anaerobic bacteria therefore has large consequences on the scientific understanding of the nitrogen cycle. The anammox process gives a new dimension to the nitrogen cycle in the oceans.

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