Role of Upflow Velocity on Aerobic Granulation

The objective of this research was to study the role of upflow velocity on aerobic granulation in UAGS (Upflow Aerobic Granular Sludge) system. The experiments were conducted under room temperature. Four UAGS reactors, 4 liters of effective volume each, were fed with synthetic wastewater (soy bean milk) at the flow rate of 0.5 liters per hour. Hydraulic retention time (HRT) then was controlled at 8 hours. Upflow velocities (controlled by effluent recirculation) of Reactor 1, 2, 3 and 4 were 0.5, 0.8, 1.2 and 1.6 meters per hour, respectively. Influent COD concentrations were in range of 700 – 1,200 milligrams per liter. After 128 days of operations, at steady state, all 4 reactors (R1, R2, R3 and R4) had similar high average COD removal efficiencies, which were 93.62 + 2.39 %, 95.50 + 2.53 %, 96.61 + 3.71 % and 96.68 + 2.57 %, respectively. Average BOD removal efficiencies were in range of 91.88 – 95.96 %. Aerobic granules in all reactors had similar granule size distribution. Most of the granule sizes were in range of 0.85 - 4.74 millimeters with the average settling velocities in range of 21.6 – 187.2 meters per hour. Upflow velocities of 0.8 - 1.2 m/hr. were recommended.