ABSTRACT
Fortunately, some forerunner explored the unknown area. de Kreuk (de Kreuk 2006) tried to cultivate aerobic granules by using pre-settled sewage as influent. After 20 days’ operation at a high Chemical Oxygen Demand (COD) loading, heterogeneous aerobic granular structures were observed, with a Sludge Volume Index (SVI) after 10 min settling of 38 ml/g and an average diameter of 1.1 mm. This led to a pilot-scale plant setup at a WasteWater Treatment Plant (WWTP) in Ede, The Netherlands. Two bubble columns with a diameter of 0.6 m and height of 6 m were used. After about one year cultivation, dry weight concentration was 10 g/L, of which 80% consisted of granular sludge with a diameter larger than 0.212 mm. The influent concentration to the SBR in their work was in a range of 270-400 mg COD/L. These results provided valuable information for potential
2 MATERIALS AND METHODS
2.1 Reactor setup and operation
A bubble column with a diameter of 20 cm, a height of 60 cm and working volume of 18.8 L was used for the cultivation of aerobic granulars. The sand disk diffuser with the same cross section area was installed at the reactor bottom for air supply and mixing. The Dissolved Oxygen (DO) concentration in the aeration stage was in the range of 2.5-6.5 mg/L. Effluent was discharged from the middle port of the reactor and the exchange ratio was 60% with a 10 h hydraulic retention time. A 12 h operation cycle was implemented in each reactor operation, comprising 5-min feeding, 700-min aeration, 3-min settling (shortened from 30-min to 3-min gradually), 5-min decanting and 7-min idling.
