Type 0092
Type 0092 is a filamentous bacterium possessing the following characteristics:
- not branched;
- immobile;
- straight/bowed filaments;
- filament length < 200 µm;
- cell diameter 0.5 - 0.7 µm;
- no attached growth;
- no sheath;
- septa not clearly visible;
- no sulphur storage;
- Gram negative;
- Neisser positive (grey-violet filaments).
Type 0092 is for the most part "hidden" in the flocs in domestic treatment plants, as a result of which only the short free ends of the filaments are visible on unstained slides. Type 0092 can be confused with H. hydrossis (Neisser negative and the filaments are usually longer). As the filaments of Type 0092 are largely concealed in the flocs, the population size of this filamentous bacterium can easily be underestimated. It is only possible to see how large the population actually is after Neisser staining.

Occurrence in activated sludge
Type 0092 commonly occurs in activated sludge. The following process conditions are favourable to this filamentous species:
- sludge loading level < ca. 0.1 kg BOD/kg MLSS.day;
- raw influent;
- water temperature > ca. 15 °C;
- ???
The population size displays a seasonal rhythm in domestic treatment plants in The Netherlands, with the maximum occurring in summer/autumn. As the filaments are largely taken up in the flocs, the effect on the SVI is small. In many treatment plants, the disappearance of M. parvicella in April/May is followed by an increase of Type 0092. It has therefore been suggested that both of these filamentous bacteria can use the same substrate. This theory has not yet been verified. Practically nothing is known of the physiology of this bacterium. Type 0092 is occasionally (dairy industry waste water) observed en masse, free in the water between the flocs.

Control strategies
Nothing definite is yet known about control strategies. It is of course possible to control symptoms only.