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

Identification

Flagellates are single-celled protists with one or more flagella, whip-like organelles often used for propulsion. The flagella is used for movement through the liquid. Some flagellates live as colonial entities, while others function as a single cell. Most are free-living organisms, however, a number are parasitic or pathogenic for animals and humans. They multiply by binary fission and some species posses cyst stages. Flagellates range in size from 5-20 µm. Many flagellates are able to feed autotrophically as well as heterotrophically.

There are two primary groups of flagellates. The Peranema belongs to the group which ingests its food. The other group of flagellates is more like bacteria. They don't ingest whole food. They take in food that is already partially "digested." Dinoflagellates are important primary producers (photosynthesizers) in lakes and oceans, yet they can also ingest prey and feed in an animal-like fashion.

Additional Information:

Flagellates are protozoa that are found in the group Mastigophora. Some types of flagellates commonly found in wastewater are Euglena, Trigonomonas, and Monas. Recently flagellates were divided into additional categories-plant-like Phytomastigophora and Zoomastigophora.

Environment

Like their relatives the amoebae, flagellates are usually present when there are large amounts of soluble food available (high F:M or high BOD). They are found during start up when the sludge is young or after an upset, but will quickly predominate over the amoebae because they are more efficient feeders. They are often found in trickling filter, oxidation ponds, lagoons and activated sludge. Flagellates may have one or two flagella or whips for locomotion. Flagellates can be color-less or green.

Flagellates are one of the few protozoan form present in sludge that is strongly loaded. Their presence may indicate high soluble BOD levels. Flagellates usually are present in very large numbers during initial start- up of a wastewater treatment plant, during recovery from a toxic discharge to the treatment plant, or at low D.O. levels. If flagellates are present as the dominant protozoan group, this could indicate an unstable wastewater environment and a sludge biomass that is very young. Usually found in low MCRT or low HRT for activated sludge systems. Lagoon systems are different and flagellates are often found in lagoons since it is harder to develop an older sludge in a lagoon with high flows.

If the biomass is really old and rotifers and nematodes are usually present, and all of a sudden large numbers of flagellates show up, check to see if a sudden spike of BOD has occurred. Adjustments to RAS and wasting may need to be made in order to handle the sudden increase in BOD. Addition of biological products can also help overcome sudden spikes in BOD to help recover quicker and reduce changes or BOD or TSS permit violations.

How to find them:

Microscopic examination of a wet mount. Some of the larger amoebae can be seen at 40-100x and 200x. Sometimes there may be tons of really small flagellates that require the use of 400x or even 1000x in order to clearly see them. This usually happens when a sudden spike of BOD has happened.

What does it mean when I see an increase in flagellates in my system?

It depends upon what the rest of the biomass looks like. If the floc is small, weak, dispersed, you may have a very young sludge age. Typically the presence of flagellates, similar to amoebae indicates a high loading of food vs. the amount of biomass available to eat the organics. Flagellates possess one advantage over their amoeboid relatives in that they can swim. Therefore, enabling them to invade and adapt to a wider range of environments unsuitable for other amoebae. Usually, this means that the sludge is a bit older than if only amoebae are present and there are probably less single celled bacteria swimming around.

It may mean the sludge is young if the floc is clear, dispersed and weak, or if you have had rotifers in the past and were old, it may mean a recent high loading of BOD that is forcing the sludge age to a younger age. Usually you can expect high solids in the effluent and higher BOD levels if flagellates are present in significant numbers. Daily microscopic analyses is helpful in documenting where you are today, where you have changed since the previous day and how to react to changes proactively as opposed to when they have become critical!

What should I do if there is a significant change in my higher life forms and all of a sudden there is an increase in flagellates?

First check to see why they have increased? Is there a change in loading that might impact other areas? Check your nutrients in this case if applicable to your plant. The biggest mistake people make when a high loading comes through or a spill, especially at industrial plants is not to increase nutrient levels when high loading occurs.

You might want to adjust your wasting or RAS levels. Some plants add bioaugmentation products in cases of higher loadings. You might need to slightly increase the dosage of product. If using micronutrients, adjust these levels also if the loading is significant.

You might need to check the Bed levels in your clarifier. Check your TSS off your clarifiers.

More to come soon!

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