Anaerobic Digester Foaming: Causes and Solutions

Anaerobic digester foaming has often plagued operators of wastewater treatment plants (WWTPs). Due to the complexity of the problem and the variables involved, it is often difficult to correctly identify the cause of the foaming. Foaming in conventional anaerobic digesters has been attributed to a number of causes from inadequate mixing to Nocardia bacteria carried over from the secondary treatment process. However, causes identified in the literature can be grouped into three main categories. Each of which are discussed separately with their respective solutions.Foaming in advanced digestion processes has not been well studied, and is a complex problem at WWTPs and can be caused by a variety of factors or combination of factors. Informal interviews were conducted with several municipalities regarding anaerobic digester foaming occurrences and operational strategies to deal with the problem. No universal solutions were found, but site- and system-specific solutions were common. The paper also includes recommendations for designers of digestion systems and a decision-tree for operators dealing with foaming problems.