Anaerobic ammonium oxidation of ammonium-rich waste streams in fixed-bed reactors.
The feasibility of anaerobic ammonium oxidation (Anammox) in fixed-bed reactors was evaluated on laboratory and pilot scales. Using synthetic wastewater, the specific nitrogen removal rate was increased from 0.05-0.1 kgNm(-3)(reactor)d(-1) to 0.35-0.38 kgNm(-3)(reactor)d(-1) within a year (T= 22-27 degrees C) in all applications. However, the anammox activity was seriously and repeatedly inhibited at prolonged high nitrite concentrations (e.g. six days at 30-50 gNO2-Nm(-3)) and recovery was always a lengthy process. But even at a moderate nitrite concentration (11+/-10 gNO2-Nm(-3)), the observed specific growth rate was only 0.018 d(-1) at 26.4+/-0.8 degrees C, which corresponds to approximately 0.025 d(-1) at 30 degrees C (doubling time: 28 days). In a second experimental period for another 250 days, one of the laboratory reactors was fed with partially nitrified sludge liquors from a domestic wastewater treatment plant (WWTP). In this case, the specific elimination rate was as high as 3.5 kgNm(-3)(reactor)d(-1) at 26-27 degrees C. Independently of the feed, the average nitrogen elimination rate lay between 80-85% in all applications. An appropriate hydraulic design is essential to prevent clogging and local nitrite inhibition in fixed-bed reactors.
EAWAG, Swiss Federal Institute for Environmental Science and Technology, Dübendorf, Switzerland. fux@eawag.ch
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Marchesi
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Brunner
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Siegrist
D001421:Bacteria, Anaerobic / Q000502:physiology*; D019149:Bioreactors; D009584:Nitrogen / Q000302:isolation & purification*; D010084:Oxidation-Reduction; D000644:Quaternary Ammonium Compounds / Q000737:chemistry / Q000378:metabolism*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014872:Water Movements
D000644:Quaternary Ammonium Compounds; D009584:Nitrogen