In order to enhance the solidÐliquid separation properties and nitrogen removal efficiency of SBR, the aerobic floc-like granules were cultivated under temporal alternating aerobic and anoxic conditions without the presence of carrier material in a SBR having 15 H/D (height/diameter) ratio. Two different effluent port positions were applied to the SBR for different selection of minimum settling velocities (over 0.6 and 0.7 m/h) of granules retained in the SBR during aerobic floc-like granule formation. The effect of different minimum settling velocities as an operational parameter on the size and solidÐliquid separation properties of floc-like granules and also the COD and nitrogen removal of SBR were evaluated. The reactor was operated 6 hours per cycle (aerobic 4.75 hours, anoxic 1.25 hours) under chemical oxygen demand (COD) loading rate of 2.5 kg/m3·d (1.3 kg acetate-COD and 1.2 kg glucose-COD). When increasing the minimum settling velocity by 0.1 m/h, the following results were observed at steady state. The nitrification efficiency was not changed at about 97% but the denitrification efficiency was improved from 78 to 97%. The COD removal efficiency was improved from 82 to 97% and the concentration of biomass in the reactor was retained at lower level at about 3,000 mg MLSS/L. The average sludge volume index (SVI) value of granules was decreased about 85 to 50 mL/g and the granule sizes were increased 0.1-0.5 mm to 1.0-2.0 mm. The required time to form granules and reach steady state was significantly shortened. Based on the results, the selection of the minimum settling velocity had a significant effect on both the physical properties of granules and the SBR performance, so it is suggested to use the minimum settling velocity as an operational parameter.

This content is only available as a PDF.
You do not currently have access to this content.