Removing biological solids and insoluble compounds requires microbes to form floc or biofilms. Many desirable wastewater microbes prefer to exist in a biofilm matrix. Extracellular Polymer Substances (EPS) are the glue in biofilm and floc. Consisting of polysaccharides, proteins, DNA, and humic substances, EPS can be either attached to the cell (capsular) or free in solution (non-capsular). In typical floc, EPS constitutes 50 - 90% of total organic matter.
The Zooglea family of microbes was one of the first wastewater organisms associated with floc formation. While not the only producer of floc forming EPS, the Zooglea family are very common in most wastewater plants and can be the cause of non-filamentous bulking, difficult to dewater biological solids, and difficult to settle floc.
Why biofilm and floc forms:
For keeping biological solids under control, you need EPS to be present in quantities that allow for binding biological solids. It is also better to have capsular EPS - attached to the cells - over free, unattached EPS. In free solution, the EPS acts much like agar or gelatin. Increasing viscosity, entrapping water, and creating the gelatinous matrix we associate with non-filamentous bulking. So what triggers the excess non-capsular EPS production?
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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