Proceedings

In the US, there is increasing interest in anaerobic digester (AD) foaming. Various groups have recently initiated research programs. These include the Water Environment Research Foundation (WERF), the Central States Water Environment Association (CSWEA), and several universities including the University of Wisconsin and Illinois Institute of Technology. This paper looks at AD foaming in terms of “true” foaming and the recently developed concept of “rapid volume expansion”. It primarily focuses on recent, on-going and completed research by WERF and CSWEA. Various causes and mechanisms are identified, including physical causes, biological causes, and chemical causes as well as operational and design causes. The most effective operational, design, and chemical “cures” observed to date are also presented.

Keywords: Anaerobic digestion, foaming, rapid volume expansion, Digester foaming, digestion survey

Introduction Biogas energy from anaerobic digesters (AD) is the energy production center of wastewater treatment plants (WWTPs). With rising costs of energy and green concerns, more and more focus is being placed on AD problems. Foaming is one of these. It is associated with:

• Upsets of Anaerobic Digesters

• Gas Piping and Handling Equipment Impacts

• Making Unsightly and Unsafe Conditions

• Damage Tanks and Equipment

There is lot of, sometimes contradictory, information in the literature as to what causes foaming are and how to cure it. Often what solves the problem in one case can cause or aggravate it elsewhere. In the following, the basics of the problem and potential cures are presented, focusing primarily on recent work done by WERF and CSWEA.

Impacts of AD Foaming There are both economic and non-economic impacts of AD foaming. Economic impacts include:

• Personnel Time

• Equipment

• Supplies

• Process Performance

• Biogas & Energy

• Outside Contract Services Non-Economic impacts include:

• Health and Safety

• Aesthetic Effects

• Odor Problems