Understanding and Controlling Foam in Anaerobic Digesters: Three Full-Scale Case Studies

Anaerobic digester (AD) foaming is a common problem in wastewater treatment plants (WWTPs). This study attempts to understand the causes and control mechanisms of AD foaming by completing full-scale studies at three municipal WWTPs located in the Midwest. The WWTPs chosen for this study are each unique in their process and foaming problems, however facilities with non-biological foaming were targeted. The full-scale studies included a detailed evaluation of each plant and various targeted operational modifications. The following operational parameters were evaluated, among others, and adjustments implemented to mitigate nuisance foaming: mixing frequency and intensity, feed rate and duration, waste activated sludge to primary sludge (WAS:PS) ratio, and foam suppression equipment.