Extracellular polymeric substances (EPS) - their role in flocculation, settling rates, dewatering, and non-filamentous bulking
i have been doing a lot or work on floc formation and how EPS fluctuates in wastewater systems. Since floc and biofilms are both microbial aggregates of living and dead microbial cells held in a matrix of extra cellular polymeric substances (EPS), I though a general guide to EPS would be useful to a lot of people faced with floc settling problems including non-filamentous or viscous bulking.
To microbes, the aggregate (colony) serves four distinct functions:
The EPS is composed of multiple compounds including (from highest to lowest percentage):
Due to the cells and the EPS having a net anionic charge, divalent cations (Ca++. Mg++) are very important to forming dense, stable aggregates. In most wastewater having 14 - 40 mg/L Ca++, and 8 - 24 mg/L Mg++ is sufficient. However, recent research has found that keeping a Divalent to Monovalent cation ratio greater than 0.5 is more important for good floc formation.
Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.
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