In a potable drinking water plant, all organics should be removed from the water before distribution. High organic inputs trigger deoxygenation. If excess organics are introduced to the system, there is potential for complete depletion of dissolved oxygen. Without oxygen, the entire aquatic community is threatened. If all oxygen is depleted, aerobic decomposition ceases and further organic breakdown is accomplished anaerobically.
Anaerobic microbes obtain energy from oxygen bound to other molecules such as sulfate compounds.
Thus, anoxic conditions result in the mobilization of many otherwise insoluble compounds. In areas of high organics there is frequently evidence of rapid sewage fungus colonization. Sewage fungus appears as slimy or fluffy cottonwool-like growths of microorganisms which may include filamentous bacteria, fungi, and protozoa such as Sphaerotilus natans, Leptomitus lacteus, and Carchesium polypinuym, respectively. The various effects of the sewage fungus masses include silt and detritus entrapment, the smothering of aquatic macrophytes, and a decrease in water flow velocities. An accumulation of sediment allows a shift in the aquatic system structure as colonization by silt-loving organisms occur.