You Have Found The Satan...!
Characteristics : Straight or smoothly curved filaments, 0.8 - 1.4 micron in width and 50 - 200 micron in length,
found extending from the floc surface. No attached growth. Cell septa without indentations are present. Cells are
rectangular (0.8 - 1.4 x 1.0 - 2.0 micron). Gram negative and Neisser negative, with Neisser positive granules
in - situ and this organism responds to the "S" test. Apical gonidia and rosettes are commonly observed. Trichomes
may taper somewhat from base to tip. A sheath is present, but difficult to detect.
Identification : Medium length, non-motile filaments (20-200 µm). Straight or smoothly curved filaments with no
branching. Cells are rectangular (0.7 x 1.2 µm) and a clear cell septa is present without indentations at the septa.
Filaments are found radiating outwards from the floc structure causing inter-floc bridging. The filament staining is
Gram negative or Gram variable when sulfur granules are present and Neisser negative with Neisser positive granules
observed frequently. Exhibits bright sulfur granules in the presence of sulfides under phase contrast (use the S-test).
Poly-ß-hydroxybutric acid (PHB) is frequently observed as dark intracellular granules. Small amounts of attached growth
may occur when not growing. Can form rosettes and the filaments can have gonidia on the tips. Rosettes are when many
filaments radiate outward from a common origin. Difficult to detect its thin sheath. Easy to identify due to its highly
refractive sulfur granules.
Similar Organisms : Type 021N is similar when in the bulk solution and with no attached growth, although Type
021N has no sheath.
Environment : This filament is usually found in environments where there are limited nutrients (Nor P). It can
also be found in wastes containing specific compounds with sulfides and/or organic acids or environments with low DO.
Sometimes found in plants with high pH in the aeration system.
Control : RAS chlorination should be definitely used if in the rapid growth phase. After chlorination, sheath
may still be present and interfere with SVI. Increase DO levels, add nutrients or lowering the pH according to the
problem. Septic wastes can be remediated by pre-aeration or pre-chlorination. Nutrient deficient wastes can be checked
by effluent values of residual NH3 and o-PO4 and should be supplemented if necessary.
Rank : Thiothrix ranks 5th in number of predominance.
