Tetrads and Nutrient Deficient Bacteria

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What is going on in my system? There is all this slime in my clarifier and in my sludge dewatering system and high TSS in my effluent!

The presence of large amounts of tetrads or Cyanobacteria in a wastewater treatment system can indicate a severe nutrient deficiency, typically nitrogen. Tetrads" most often are a type of cyanobacteria when found present in high levels in wastewater.

This group of bacteria may look different. It may be in clusters or groups of 4  depending upon whether it is caused by nutrient deficiency from N or P  Technically consider this a group of bacteria with similar looks. Don't get overly technical.

When trying to determine species, stick to the basics, and focus on the causes and controls of the bacteria present. The main point of any Biomass identification is not to get a PhD, but to fix your plant!

Identification

Tetrads are large cells grouped in clusters or groupings of four. Cyanobacteria or Blue-Green Algae
Cyanobacteria are photosynthetic procaryotes. Cyanobacteria are the largest and most diverse group of photosynthetic bacteria  Cyanobacteria differ from other photosynthetic procaryotes in that they carry out oxygenic photosynthesis with water as the electron donor for photosynthesis. They are true procaryotes and represent a very diverse group in terms of morphologies. Some form cells that are specialized for nitrogen fixation (heterocysts) or resting cells (akinetes). They grow in nearly all environments where phosphorous supplies are sufficient to support growth.

Cyanobacteria may assimilate simple organic compounds while using carbon dioxide as the major carbon source.
They usually cannot grow in the dark.  Many species can use atmospheric nitrogen as sole nitrogen source, i.e. they can fix nitrogen when there is not enough in the water. This is why they are usually found in papermill lagoons when N is limited, yet there is plenty of BOD or food to be found.   They are photolithoautotrophs but some can grow slowly in the dark as chemoheterotrophs.  Some species can carry out anoxygenic photosynthesis if in an anaerobic environment. Cyanobacteria as a species can vary greatly in shape and appearance; they can be unicellular; have colonies of many shapes or clusters , or can even form filaments called trichomes - rows of bacterial cells that are in close contact with one another over a large area. 

Many filamentous cyanobacteria can fix atmospheric nitrogen in special cells called
heterocysts. Filamentous cyanobacteria have a gliding motility.   They often use gas vesicles to move vertically in the water.
 
Some marine species lack flagella but are able to move by an unknown mechanism.  They reproduce by binary fission, budding fragmentation and multiple fission. Some cyanobacteria form linear filaments; others produce branches or aggregates.  Some cyanobacteria use multiple fission to produce small reproductive cells called
baeocytes. 
 
Cyanobacteria Growth requirements are two gases, CO2 and N2, along with inorganic nutrients (such as phosphorus) with water used as the electron donor. They may produce water toxins during "blooms". They almost always cause high TSS  and final effluent problems since they do not settle well.  With a Neisser staining, they are almost always purple.  They have typical procaryotic structures with a gram-negative cell wall.

Similar Organisms

Environment

Tetrads and cyanobacteria are usually found in environments where there are low levels of nitrogen present. They are usually common in a lagoons and are often found in papermill wastewater lagoons. They can cause serious TSS problems if left alone.  Usually increasing nitrogen levels in the influent often causes them to disappear quite quickly as opposed to adding high levels of polymer to try to drop them out.   Cyanobacteria are tolerant of environmental extremes, thermophilic species can grow at temperatures up to 75 degrees C.

Control:

Low nutrient levels and high BOD are  usually the cause of tetrads and cyanobacteria. Ammonia should be increased in the influent  and usually with a little bit of time they disappear.

Problems associated with Tetrads: Tetrads in wastewater systems are often a cause of high TSS. Permit violations  quite often occur found when high levels are present.

Notice in the photos how large the cells are compared to the normal bacteria making up the floc structures. Also notice that the floc forming bacteria usually are mostly Neisser negative and the tetrads are Neisser positive.  There also may be some POA or GOA

We hope you like the new look of our Filamentous Bacteria Identification Sheets

If you would like more information on filaments, you might want to consider purchasing our Filamentous Identification the Easy Way Training materials.

We also have our lab that can perform a Filamentous identification lab analyses of your own MLSS for more information

For more information on Filamentous Identification

Zooglea

 Yeast and Fungi

More photos to come. . .