Filaments and Bacteria...
Volume - 8...

Appendix - 2...

Higher Life Forms...

Microscopic observation, for analysis purposes, of protozoa and other higher life forms in activated sludge is common. Generally the types present are indicative of plant performance and effluent quality. These organism can also be used as indictors of toxicity. These organisms are a necessary component of activated sludge and perform a number of functions :

§ Coliform and pathogen removal through feeding activated which yield a clarified effluent.
§ Contribute to biomass flocculation by production of mucus.
§ Contribute to the break up of large floc masses due to motility.

The main higher life forms observed are as follows :

§ Protozoa
§ Rotifers
§ Nematodes and Annelids

Protozoa...

The protozoa are the main group of higher life forms looked for upon microscopic examination of an activated sludge sample. They are unicellular organisms and comprise the following :

§ Flagellates e.g. Euglena
§ Rhizopoda e.g. Amoebae
§ Ciliates. These can be further divided into :
- Free swimming ciliates e.g. Paramecium sp.
- Attached/stalked ciliates e.g. Vorticalla sp., Carchesium sp.
- Creeping ciliates e.g., Aspdisca sp.

Protozoa are useful indicator organisms is an activated sludge, since in general, a sludge is suggested to be in a poor condition when there are few ciliates and many flagellates present. The latter diminish as the sludge improves, until, in a good sludge, ciliates predominate.

Rotifers...

These are much larger and more complex in structure than the Protozoa. They are multicellular organisms. They tend to be able to expand and contract. They possess a “tail and a head”. Most are motile and attach to flocs by a contractile “root”.

Nematodes...

Long cylindrical bodies. Multicellular, the end of the body is thinner than the central part. Nematodes are large enough to be seen at low magnification. They will be very motile and difficult to maintain in view.

What Determines the Presence of Higher Life Forms ?...

Most have growth rates of one per day or higher. Food availability larger determines the predominance of a group. ( a ) High prey density : Flagellates, amoebae and some small free swimming ciliates require a high prey density – greater than 106 or 107 per ml. They require a high prey density because of inefficient chase and capture feeding mechanism. ( b ) Lower prey densities : At long SRT, low F/M, and lower prey densities, attached ciliates and rotifers predominate as they attached to the flocs and they also feed by ciliary action ( filter feed). The table below summaries this :

Higher Life Forms Observed Versus Organic Loading ( F : M )
Conditions	Predomimant Groups
Low Organic Loading	Stalked Rotifers and Nematodes
Optimum Organic Loading	Good diversity of organisms, dominated by free-swimming and stalked ciliates
High Organic Loading	Flagellates, Rhizopoda, Free swimming ciliates
Toxicity assessment is on of the most valuable applications of microscopic observation of micro-organisms in activated sludge. Ciliates and rotifers are amongst the first to be impacted by toxic materials. In severe cases they die, which can result in foaming. Heavy metals and cyanide in particular have a stressful effect on these organisms.