Influence of hydrodynamic shear force on kinetics characteristic of anammox granular sludge

The effect of hydrodynamic shear force on the nitrogen removal performance of anaerobic ammonium oxidation (anammox) granules was studied in four batch-type Expanded Granular Sludge Bed (EGSB) reactors. The reactors were operated under different hydrodynamic shear force (0.021, 0.024, 0.026 and 0.029 N m, respectively) by control the circulation flow rate. The results showed that nitrite and ammonia removal efficiencies increased in four reactors, firstly, and then decreased with the increase in hydrodynamic shearing force. The variation of the maximum degradation rate (v max ) of ammonia displayed in the same way. The variation of ammonia half-saturation velocity constant (Ks) was quite opposite to that of the maximum degradation rate. The maximum degradation rate of ammonia of 0.25 d was obtained when the shear force was 0.024 N·m. Increasing the shear force from 0.024 to 0.029 N m resulted in a decrease in microorganism affinity to ammonia, the increase of half-saturation velocity constant from 36.61 to 44.47 mg L was measured. The research indicates that hydrodynamic shear force can be manipulated, as a control parameter, to optimize operation of anammox reactor.