| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 642601 | Separation and Purification Technology | 2011 | 8 Pages |
Aerobic sludge granulation is rather difficult or impossible for the treatment of low-strength wastewater. In this study, a novel technique involving granular activated carbon (GAC) was developed for rapid aerobic granulation under a low organic loading condition. Laboratory experiments were conducted with two sequencing batch reactors (SBRs) running side by side. One reactor had fine GAC added to the sludge mixture, and the other had no GAC added. A low-strength organic wastewater with a chemical oxygen demand (COD) concentration of only 200 mg/L was used as the influent to the SBRs. The morphology, physical properties, and bacterial community structure of the sludge in the two reactors were characterized and compared throughout the experiments. The results showed that granules could not be formed in the SBR without added GAC. However, complete granulation was achieved in the SBR with GAC addition. Selective discharge of slow settling sludge was also essential to the granulation process. Adding GAC to the seed sludge mixture, together with the selective discharge of small and loose sludge flocs, facilitated the retention and growth of bacterial cells on GAC in attached-growth mode, leading to complete granulation. In addition, the use of GAC produced aerobic granules with strong cores to help maintain the long-term stability of mature granules. With granulation, the solid–liquid separation property of the sludge was greatly improved. Once granules were formed, the granules were quite stable and GAC addition was no longer needed. Therefore, adding GAC is a simple and effective strategy to initiate granule formation for complete sludge granulation in bioreactors treating low-strength organic wastewater.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Use of GAC makes aerobic granulation in SBR possible for a low COD influent. ► Initial GAC addition facilitates attached biofilm growth and granule formation. ► Selective discharge of slow settling sludge flocs is also essential to granulation. ► GAC produces granules with strong cores to help maintain their long-term stability. ► Once granules are formed, adding GAC is no longer necessary even for low loadings.
