Proceedings

ABSTRACT
Anaerobic digester foaming has raised concern to operators and managers due to the adverse impacts of foaming on the
overall digestion process. In this study, 13 UK Sewage Treatment Works were visited and the foaming propensity of sludges
was investigated. The sludges quality characteristics were determined. Sludge samples obtained from foaming sites produced
higher foam volumes in laboratory conditions than sludge samples obtained from non foaming sites. The foaming propensity
of sludges obtained from foaming sites did not show clear correlations with foaming at the full scale. SAS samples obtained
from foaming and non foaming sites did not generate foam in laboratory conditions apart from SAS obtained from one foaming
site. Analysis of sludge samples from foaming and non foaming sites demonstrated that digesters can foam when there is no
indication of overloading and when the digested sludge quality characteristics are within the suggested ranges. Further work
will concentrate on the role of filamentous microorganisms in AD foaming and the changes in filaments population during
anaerobic digestion.