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Coping with Digester Foaming in an Age of Increasing Incidence

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Digester foaming is poorly understood. An increasing number of wastewater utilities are experiencing significant disruption of both liquid stream treatment and solids processing operations as a result of foaming episodes and, in some cases, costly structural damage to their digesters. A review of the literature indicates that we should anticipate increased foaming problems in the future as the use of biological nutrient removal (BNR) and membrane (MBR) processes become more prevalent, and as utilities operate at lower DO concentrations to contain operating costs and reduce their carbon footprint. This paper reviews research findings and actual operating experience related to digester foaming and describes foam formation and its behavior inside the digester. Measures to reduce the impacts of digester foaming such as changes in digester operational practices and facility and equipment modifications that can make a digestion complex more “foam tolerant” are reviewed, along with the prospects for their success based on observations at operating plants. Merely optimizing operational practices may not be sufficient in all cases, and some wastewater utilities have opted to make major process changes in an effort to reduce digester foaming. Early operating experience with two phase digestion, in particular, has shown considerable promise at several treatment plants with long histories of foaming in conventional digestion systems. Short of undertaking major capital improvements to effect process changes, there are more modest steps that can be taken to reduce the potential for facility damage and disruption from digester foaming.

Keywords: Anaerobic digestion; digester foaming; filamentous organisms; surface-active materials; surfactants

Document Type: Research Article


Publication date: 2009-01-01

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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