Survey of Causes and Prevention/Control of Anaerobic Digester Foaming — A WERF Study

A survey of anaerobic digester (AD) foaming in wastewater treatment plants in USA was carried out from April 2011 to August 2011. Of the 39 plants surveyed, 32 had experienced foaming in the past five years or were experiencing foaming currently. The presence of foam causing filaments was found to be the most common cause of foaming, followed by the feed sludge quality and the presence of FOG and other surface active materials in the feed to the digester. While no specific relationships between process parameters and causes of foaming were established, the survey responses helped compare full scale plants' information with the several available sources of information on AD foaming. Though specific groups of causes have been identified, roles of certain factors as causes or contributors cannot be still ascertained. Major deficiencies also exist in the current understanding of effective remedial actions for foam mitigation. Our survey also indicates that the use of antifoam chemicals has been reported to be effective for mitigating digester foaming.