Thiothrix

Identification

• Has rectangular-shaped cells
• Stains Gram negative
• Can have sulfur granules

Why Do I Have It?

• Low D.O. conditions
• Sulfites and sulfides present

Treatment

To reduce the abundance of Thiothrix, we recommend increasing aeration to raise the oxidation/reduction potential in your wastewater plant. If increasing aeration is not possible, Aquafix recommends the addition of OxyFresh to help combat low dissolved oxygen levels. If you are having difficulties maintaining adequate D.O. levels, we recommend consulting with us to address potential issues with aeration or overloading.

Because wastewater issues and the cause behind filaments can be complex, we recommend our Filament ID and Microanalysis. This not only confirms organism ID, but looks at biological indicators, plant design, and incoming substrates to decode your unique process.

Under the Microscope and in Your Plant

Thiothrix is a common bulking filament. It is categorized into two different filament groups, Thiothrix I and Thiothrix II. Thiothrix I is slightly wider (1.6-2.5 µm) than Thiothrix II (0.8-1.4 µm). Due their shared genus, these filaments are usually grouped together. Thiothrix prefers conditions with low levels of dissolved oxygen, incoming septic waste, nitrogen deficiency, and/or sulfur-reducing conditions. Thiothrix can be identified using 1000x magnification. These filaments have rectangular cells that regularly store sulfur granules. However, Thiothrix may not always have sulfur granules, making identification difficult. To circumvent this, Thiothrix can be forced to store sulfur granules by conducting an S test. This is done by exposing a sample to sodium sulfide for 10-15 minutes, allowing sulfur to be stored in granular form within the filaments to confirm identification. These granules can be viewed under 400x magnification using phase contrast. Thiothrix is a genus of filament species which includes Type 021N. It tends to be thicker than other Thiothrix forms and tends to have disk shaped, cells, rather than rectangular cells. Type 021N is separated out from the rest of the genus for identification and treatment purposes because it does not readily store sulfur like the rest of the filaments in this genus. Thiothrix stains Gram negative, however, it can occasionally contain Gram positive granules. If Thiothrix grows rapidly enough, rosettes are formed. Rosettes are when multiple filaments extend around the same center point, forming an asterisk-like shape.