THE ROOT CAUSE OF EXCESSIVE ANAEROBIC DIGESTER FOAMING

Excessive foaming in anaerobic digesters has been a problem for many years. All anaerobic digestion 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 for foaming include presence of excessive filamentous bacteria, excessive oils and grease, and the feed sludge composition - primary sludge (PS) versus waste activated sludge (WAS), but the chief cause of excessive foaming is inconsistent feed to the digesters.Monitoring and consistent feeding are vital to successful digester operation and to minimizing excessive foaming events. Three case studies will be presented demonstrating an effective monitoring program to control volatile solids loading to the digester were used to eliminate excessive foaming events. Following the case studies a general discussion of recommended operational strategy is presented, and conclusions.