Evaluation of the Recovery of Stored Granules to Promote Practical Wastewater Treatment by Aerobic Granular Sludge Process

Aerobic granular sludge (AGS) application for wastewater treatment has been proven to have high sludge-water separation efficiency, great treatment capacity, and strong tolerance to toxic and harmful substances. Nevertheless, the AGS storage and recovery issue has only been studied in a few research. This paper studied the optimized condition for reactivation of the AGS after 3 years storage in distilled water at 4°C. The initial results revealed that under the synthetic wastewater conditions of 450 ± 0.5 mg COD/L, 65 ± 0.2 mg NH4+-N/L, 15 ± 0.1 mg PO43–-P/L, and the DO concentration was controlled at 20% of the saturation oxygen, it took about 30 days to gain the same volume of AGS as before storage, but not the granular size. The aeration time was susceptible to the growth of bacterial aggregates. The optimum aeration time of 172 minutes was chosen to achieve up to 11.58 g/L MLSS and 46.73 mL/g SVI30. With that reactivated AGS, substantially high organic and nutrient removal efficiencies were obtained with 97.8%, 100%, and 86.7% for COD, NH4+-N, and PO43--P, respectively. The future study will apply real domestic wastewater with different organic and nutrient loadings to test its stability and reproducibility in these specific culture conditions.