Long-Term Study of an Activated Sludge System Exhibiting a Seasonal Biological Foaming Problem

摘要

Biological foaming is a widespread problem in the USA and in the world. Although greatprogress has been made with respect to identifying the microorganisms and the physicalprincipals – causing foaming, the fundamental ecological mechanisms leading to foam formationremain ambiguous and illusive. Thus, general design and operation guidelines to avoid foaminghave not found widespread use. In this study, we investigate the seasonal biological foamingproblem at the Urbana-Champaign Sanitary District Northeast plant. We show that variation intemperature is the main factor contributing to the observed phenomenon. Further statisticalanalyses support the proposal that foam-causing organisms are specialists of the degradation ofslowly degradable substrates (presumably lipids). According to this proposal, temperatureselects for these organisms during the summer by increasing the degradation kinetics of theirsubstrates. As a secondary mechanism, high concentrations of mixed liquor suspended solids(MLSS) are found to render the plant more prone to biological foaming. This suggests that thesuccessful reports of control of biological foaming by means of increase sludge wastage can bedue to both the washout of the foam-causing population and the reduction in MLSS.