Design and Operational Considerations to Avoid Excessive Anaerobic Digester Foaming
Abstract:Excessive foaming in anaerobic digesters has been a problem for many years. All anaerobic digesters will foam to some extent, but excessive foam can be problematic. Excessive foaming is defined as foam that interferes with flow through the gas piping system and/or is not contained within the digester. Causes of foaming include presence of excessive filamentous bacteria, extreme amounts of oils and grease, and the feed sludge composition (primary sludge (PS) versus waste activated sludge), but the chief cause of excessive foaming is inconsistent feed to the digesters.
Many utilities have evaluated technological changes to the digester facilities. While such changes may reduce/control foaming, they often involve expensive additions to the facility in terms of both capital and operation and maintenance (O&M) costs. Consequently, before investing in technology changes, utilities should consider operational changes that could mitigate foaming.
In addition, facilities that are installing new digesters should consider design elements that can reduce the potential for foaming as well as the effects of foaming on ancillary equipment. Design considerations to avoid excessive digester foaming will be presented followed by three case studies of unstable operations at existing digester facilities, and operational considerations to avoid excessive foaming will be presented in relationship to the three case studies.
Document Type: Research Article
Publication date: 2006-01-01
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