July 24, 2003
Development of a high-efficiency denitrification system High-speed processing can be realized by grain-shaped growth of microorganisms for Anammox
Kurita Water Industries, Ltd. (Headquarters: Shinjuku-ku, Tokyo; President: Hiroshi Fujino) has developed a new biological nitrogen removal process which uses denitrifying microorganisms known as ANAMMOX (ANAerobic AMMonium Oxidation) microorganisms.
Anammox™ process can reduce caital investment and operational costs dramatically compared to the conventional nitrification-denitrification process.
In conventional processes, ammonia or organic nitrogen in wastewater is totally oxidized to nitrate under aerobic condition, and nitrate is then converted to dinitrogen gas under anoxic condition. In denitrifying step, organic materials like methanol are needed as an electron donor for the reaction.
Anammox™ process consists of two reactors, named nitritation and Anammox™.
In the nitritation reactor, half of the ammonia is oxidized to nitrite, and ammonia and nitrite are converted to nitrogen gas in Anammox™ reactor.
In this regard, energy for the aeration in the nitritaion could be reduced about by half, and in Anammox™ reactor no additional BOD is needed for denitrification because ammonia acts as an electron donor. Since reactions are done by autotrophic bacteria, about 70% of excess sludge could be reduced compared to the conventional process.
Pathway of the conventional process and Anammox™ process
Anammox™ microorganisms were first discovered in 1990 by a research group of Technical University of Delft in the Netherlands.
Kurita Water Industries had formed a partnership with PAQUES BV in the Netherlands, the first contractor of Anammox™ process in the world.
Kurita and Prof. Furukawa, Department of Civil Engineering Kumamoto University, discovered ANAMMOX microorganisms from wastewater treatment plant in Japan.
Kurita has developed "sludge granulation technology" to keep high concentration of ANAMMOX microorganisms in the reactor.
This technology uses UASB (Upflow Anaerobic Sludge Blanket) granule as an initial carrier for starting up of Anammox™ reactor and reactor can maintain 40 to 50 g/L of SS (Suspended Solid) concentrations and volumetric loading of 5 to 7 kgN/m3/d can be achieved.
This loading rate is approximately 5 to 10 times higher than that for conventional denitrification process, and area requirement could be greatly reduced.
In nitritation process, key factor for stable operation is how to avoid growth of nitrite oxidizing microorganisms.
Kurita has developed new reactor which can eliminate nitrite oxidizing microorganisms.
Combination of this technologies and DNA analysis of ammonia and nitrite oxidizing microorganisms, stable operation of nitritation process could be achieved.
Pilot-scale experiments of Anammox™ process were done for the treatment of reject water from anaerobic sludge digestion in wastewater treatment plant located in Niigata prefecture.
Experiments had continued for two years and finished successfully, and efficiency and stability of Anammox™ process were confirmed.
KWI has started sales promotion activities of Anammox™ process for treatment of wastewater with high (over 200mgN/L) concentration of ammonia or organic nitrogen.
Main target will be, reject water from anaerobic sludge digestion, and wastewaters from chemical industries, food industries, and power plant.
Results of pilot scale experiments were presented at 40th Annual Technical Conference by JSWA (Japan Sewage Works Association).
Another presentation with regarding granulation technology of Anammox™ microorganisms was presented at 6th International Symposium on Strong Nitrogenous and Agro-Wastewater, held by IWA (International Water Association), and obtained the award for the best paper of the symposium!