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Zoogloea

Once thought to be the only floc-forming bacteria, this “classical floc-former” exists in 2 forms within activated sludge, fingered Zoogloea and amorphous Zoogloea. Fingered Zoogloea have many branches that look like “fingers” and resemble the pseudopodia (false feet) of amoebae. These organisms may proliferate in activated sludge to the extent that sludge settling is hindered (Zoogloeal bulking). Large masses of this dendritic form may physically interfere in sludge settling and compaction similar to filamentous bulking. Excessive Zoogloea is usually the result of a high F/M (food-to-microorganism ratio), especially when the wastes contain soluble, readily degraded organic compounds such as soluble sugars or simple organic acids (from septic areas). Nutrient deficiency can also be a factor, leading to slime bulking. When insufficient nitrogen and/or phosphorus are available to produce necessary cell components (such as proteins), substantial amounts of exocellular polysaccharides (“slime”) are produced. This jelly-like consistency to the activated sludge can interfere with sludge compaction.