Family VAGINICOLIDAE
Genus Vaginicola

Key to the species of Vaginicola;
     Two large (120 micron) zooids protruding from a single lorica (V. crystallina)
     Single small (50 micron) plump, zooid protruding from the lorica (V. striata)

Both species are very rare. Seen at the Green Bay Metropolitan Sewerage District only during the summer months.

Images above.
(L) Gram stain at 200X showing the light colored lorica and darker colored zooids.
(Center two) Wet mounts of V. crystallina.
(R) V. striata.
(photos and descriptions courtesy of Jack Boex at GBMSD)

Zoogloeal (amorphous and fingered)

Indicative of several conditions. Both types of Zoogloeal are most often observed in high F/M systems, especially if the waste contains readily biodegradable, soluble organic compounds and the pH is low. For those reasons amorphous zoogloea often develops in selector systems.

At the Green Bay facility, Zoogloeal colonies only become a problem during the annual food-canning season. GBMSD utilizes a single stage nitrification/denitrification with biological phosphorous removal process. The F/M within the aeration section of the plant during canning season is approximately .1-.15. The F/M's within the anoxic zone will climb to greater than 2.0. Due to this, and also that the incoming canning waste is highly soluble can lead to zoogloeal growth.

Images above.
(L) Gram stain at 200X of fingered Zoogloeal.
(Center) Gram stain at 200X of fingered Zoogloeal.
(R) Wet mount at 100X of fingered Zoogloeal.
(photos and descriptions courtesy of Jack Boex at GBMSD)

Neisser positive staining Tetrads and Neisser positive staining bacterium.

Group of four cells, termed Neisser positive tetrad. Can cause dispersed growth and a turbid effluent. Related to both nutrient deficiency and low F/M operation.

Bacterium grow in grape-like clusters inside the activated sludge floc in systems with initial anoxic or anaerobic zones. The cell clumps are thought to be Acinetobacters and the Neisser positive staining reaction is thought to be associated with internally stored inorganic polyphosphate granules that accumulate when these organisms are cycled through an anaerobic/aerobic environment. These types of Neisser-positive staining cells are found in significant amounts in activated sludge systems exhibiting EBPR (enhanced biological phosphorus removal).

At the Green Bay plant, both the tetrads and bacterium are common. Green Bay utilizes an anoxic zone that also serves as the anaerobic zone for the biological phosphorous removal system. Even though the plant influent has a C:N:P ratio of approximately 100:10:2 the nutrients are taken up so rapidly resulting in nutrient deficient conditions.

Images above.
(L) Group of Neisser positive staining tetrads clearly showing the four cell structure.
(Center and R) Neisser positive staining tetrads and darker colored bunches of the bacterium.
(photos and descriptions courtesy of Jack Boex at GBMSD)

Nocardia spp.

Irregularly bent, short filaments, 1.0 um in diameter and 5-30 um in length. Found mostly within the floc but also free in the bulk solution, especially when foam is trapped in an aeration basin. A true branching mycelium often is observed. No sheath and no attached growth occur. Cell shape is somewhat irregular (1.0 X 1.0 to 2.0 um), and septa without constrictions are clearly visible. The filament is Gram positive and Neisser negative, and Neisser positive granules commonly are observed. No sulfur granules are present. PHB granules commonly observed. The abundance of this organism is best assessed from the Gram stained preparation.

Images above.
(L) Gram stain at 200X.
(Center) PHB stain under oil immersion at 1000X.
(R) Neisser stain under oil immersion at 1000X.

Green Bay has a good population of Nocardia spp. at all times, but the filament is kept under control by occasionally adding hypochlorite to the RAS stream and by not allowing the MCRT to go beyond approximately 12-14 days.
(photos and descriptions courtesy of Jack Boex at GBMSD)

Bristleworm and Waterbear

Waterbears (Tardigrades) are fascinating critters! They are one of the most resilient types of animal known, able to withstand temperatures from -272ºC to 151ºC and X-ray radiation 1000x times the human lethal dose. When a piece of dried-up moss which had been kept in a museum for 120 years was moistened, hibernating tardigrades successfully recovered from within the moss.

A nice link regarding Tardigrades.

Wastewater Microbiology Web Links

Activated Sludge Microbiology and Control - Toni Glympth (WI DNR)

Wastewater Microorganism Gallery - Steve Duerre (Minnesota PCA)