Anammox Definition
- Anammox(Anaerobic Ammonim Oxidation) is a reaction where NH4+-N is used as an electron donor and NO2--N is used as electron acceptor. At anaerobic condition these reactants are converted into nitrogen gas and NO3--N. This reaction is carried out by an Anammox bacteria which is used for nitrogen removal from the wastewater as an Anammox process. Since Anammox bacteria uses NO2--N, which is an intermediate during nitrification, and NH4+-N, which is contained in the influent, under anaerobic condition there is a big difference between the Anammox process and the conventional nitrogen removal process.
Advantage and disadvantage of Anammox process
· The loading rate of Anammox process is very high about 2.6kgN/m3·day and therfore the reactor could be very compact. However the nitrogen loading rate of conventional activated sludge is only 0.1kg N/m3·day.
· Since the Anammox bacteria is classified as an autotrophic and therefore the external carbon source is not required. Also it consumes NO2--N as an electron acceptor the oxygen is not necessary for respiration.
· However the Anammox bacteria grows so slowly it requires long SRT(Solids Retention Time) to maintain the bacteria in the reactor.
· It is possible to maximize the treatment efficiency under high NH44+-N concentration and higher than 30℃ in the influent.
· Since the aeration rate is very low it is possible to reduce production rate of dispersed offensive odor.
· There is an advantage that the sludge production is very low.
Recent trend of Anammox
· The PN/A(partial nitrification and Anammox) process has been applied dominantly at Europe. Recently its application is increasing for treating the reject water in the wastewater treatment plant at North America.
· Early days the two-stage reactors or existing SHARON(Single reactor system for High Ammonium Removal Over Nitrite) process has been used for precise control.
· Recent days the single-stage system is becoming poplar and the MBBR, the granular reactor, and the SBR process are applied.
· The SBR process occupies about 50% of all installations and 88% of them use single reactor system. 75% of them are installed for treating the digester centrate or sludge reject water in the wastewater treatment plant.
· Among SBR applications more than 80% of those adopt the DOMONⓇ process which is patented based on the input control method with pH.
· A technology is developed recently to control the rotation speed and submergence in RBC based on the real-time ammonia and DO measurements at the fertilizer plant in the Netherlands. This plant treats 150 kg nitrogen in a day.
· The Purac developed a biofilm process and named DeAmmonⓇ. It was applied for the first time to treat the reject water at the wastewater treatment plant of Hattingen city in Germany.
· The Veolia developed a single-stage MBBR process and named ANITAMoxTM. It does business not only wastewater treatment but also supplying Anammox seed bacteria which are attached to the media.
· In addition other companies are practising various Anammox processes such as the PANDA, NASⓇ, or TERRANAⓇ at the filed plants.