Influence of gas flow-induced shear stress on the operation of the Anammox process in a SBR.
The start up and performance of the Anammox process were tested in sequencing batch reactors with two different configurations: a bubble column (SBR-B) and a gas-lift reactor (SBR-G). Different off-gas upflow velocities were tested (3.53-12.3 cm min(-1)) in order to expose the biomass to different shear conditions and to study their effects on both efficiency and physical properties of the Anammox granular biomass. For the SBR-B the minimum gas upflow velocity needed to achieve biomass suspension inside the reactor was 12.3 cm min(-1). Such velocity made impossible the stable operation of the process. The fluidization of biomass for the SBR-G was reached at a gas upflow velocity of 3.52 cm min(-1). This system maintained an efficiency of nitrite removal around 98% at values up to 5.29 cm min(-1) but when the gas upflow velocity was increased from 5.29 to 9.70 cm min(-1) a significant decrease of the specific Anammox activity of the biomass from 0.35 to 0.05 g Ng(-1) VSS d(-1) was measured. The system lost 85% of its nitrogen removal efficiency which was not restored in spite of returning the gas upflow velocity to its initial value.
Department of Chemical Engineering, School of Engineering, University of Santiago de Compostela, Rúa Lope Gómez de Marzoa s/n, E-15782 Santiago de Compostela, Spain.
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D000392:Air Movements; D019149:Bioreactors; D013314:Stress, Mechanical; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*