You Have Found The Satan...!
Characteristics : Straight or slightly bent filaments, 0.6 - 0.8 micron in diameter and 20 - 80 micron in length,
found extending from the floc surface. Cells are rectangular ( 0.6 - 0.8 x 1.0 - 2.0 micron ) without constrictions at
septa. No sheath, no attached growth. Gram negative and Neisser negative. No sulfur granules. This filament appears
"transparent", as does Type 0961.
Identification : Medium length, non-motile filaments ( 100 - 300 micron ). Straight or bent filaments with no branching. Cells are rectangular ( 0.8 x 1.5- 2.5 micron ) and with a rigid trichome. There are no indentations at the
septa. Filaments are found extending from the floc surface forming an open, loose floc structure. Usually are observed as bundles in the bulk solution. The filament staining is weakly Gram positive with a beaded effect and Neisser negative.
Sparse attached growth. Usually easy to identify due to the attached growth that is perpendicular to the surface of the filament. No sulfur granules. Sheath is present but sometimes hard to observe.
Similar Organisms : Type 0675 is similar although is usually smaller and has heavier attached growth and doesn’t
grow in bundles.
Environment : This filament is usually found in environments where there low F / M with a long MCRT. This can be
either a high MLSS concentration or a low BOD loading ( < 0.2 lbs BOD / lbs MLSS . day ).
Control : F/M can be changed by intermittent feeding, increased sludge wasting, changing from complete mix to
plug flow or use of a selector. RAS chlorination should be used.
Rank : Type 1851 is ranked 13th in predominance.
Comment : In the archive, Type 1851 on the left and Type 0675 with the attached growth on the right in both photos. See in the stained photo above how the size of the cells are slightly smaller on the 1851, but the orientation of the attached growth is always a dead give away for this filament. It almost always is just one single celled bacteria at opposites alternating, whereas type 1675 can have tons depending upon the sample and age of the biomass.
