1985 Volume 21 Pages 153-163
A multi-staged upflow sludge bed reactor was applied to denitrification process with an aim to enhance the process performance for the treatment of wastewater containing high strength nitrate nitrogen. The denitrifying cells grown in the upflow environment had a tendency to form granular sludge, whose settlability was significantly superior, i.e., SVI of sludge was achieved less than 10 (ml/g). Therefore, the granulation of sludge caused the maximum attainable biomass hold-up in the reactor to be 110, 000 mg/liter as MLVSS equivalence. The retainment of high concentration of biomass leads to increase allowable volumetric loading rate to an order of magnitude greater, compared with that in conventional suspended growth system. From the continuous flow runs varied the influent substrate in the range of 200 to 800 mg NO3-N/liter, the consumptive ratio, the true growth yield and the maintenance coefficient in USB reactor were evaluated to be 0.82 (g TOC removed/g NO3-N reduced), 0.334 (g VSS/g NO3-N) and 0.017 (g NO3-N/g VSS·day), respectively. The progress of granulation was observed to be associated with the accumulation of extracellular polymer content in the sludge. In addition, the secondary effect of precipitation of insoluble Ca-salts in the sludge granules caused more improvement of their settlability.
