Typically the organisms represent only 5% of the biomass. They are usually the last to come and the first to go in a system if it is not running properly.

Filaments present in the system do not always have to mean a problem. Some filaments are good if they form a strong backbone and add a rigid network to the floc. In just the right amount filaments help give the floc more structure and settle faster. Filaments are excellent  BOD degraders also. They typically only cause a problem when they become dominant over the floc formers.

The presence of large amounts of yeast can indicate a low pH, existence of fermentative conditions or a severe phosphorous deficiency.

Zooglea can be extremely large, non-motile bacteria. They can be either  "fingered or amorphous".  Zooglea grow usually as "amorphous" clumps or "fingered" like a tree. They can have the ability to denitrify. Zooglea usually have the presence of excessive amounts of polysaccharide coating. This can cause sliming problems in a clarifier or if excessive when trying to dewater the solids.  They can sometimes indicate low pH in the system. This bacteria is usually found in environments where there is a high F/M ratio where the soluble organic compounds are readily bio-degradable. They are often present in selector systems in activated sludge. They also can be an indication of nutrient deficiency (Nitrogen or Phosphorus).

Tetrads are autotrophic bacteria capable of utilizing elemental nitrogen as a nutrient/energy source. They are usually indicative of a severe ammonia deficiency.  Generally they can only detected by using Neisser stains or by using higher magnification under the microscope.  They almost always contribute to higher levels of TSS  in the final effluent.

India Ink Stain- Negative or reverse staining for polysaccharide coating. India Ink is used as a quick and dirty test to tell one of two things.

This is an excellent quick and dirty test that can be used daily. One drop of India ink is added to one drop of the biomass. Everything will be dark except for the polymer generated by the biomass. A normal biomass will have some bright areas relative to the size of the floc structures. Extremely bright or excessive areas will indicate one of two things. A toxic shock to the system or nutrient deficiency. If there are higher life forms present, then a shock can instantly be ruled out and nutrient deficiency can be verified.

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