Using microscopic exam can detect a high loading or spill event in wastewater systems

Active stalk ciliate attached to floc.

I am a big proponent of using quick microscopic exams in wastewater treatment systems. The basic exam includes the following:

• Floc size & density
• Free bacteria cells in solution (at 400x magnification this looks like small rods or circles bouncing around)
• If septicity is a common problem note the number of spirochetes
• Protozoa - note numbers of amoeba, flagellates, free swimming ciliates, crawling ciliates, and stalk ciliates
• Metazoa - any rotifers or worms should be noted

Once you have baseline microscopic information for light, normal and heavy loadings; microscopic exams become much more powerful for influent quality diagnostics. Within hours of a heavy or shock loading event, you will see an increase in free bacteria (this means you have moved back on the growth curve to log phase growth). Flagellates that feed on the free bacteria often increase shortly after the free bacteria increase. If the loading is depressing D.O. or toxic to organisms, you will lose the stalk and some of the free swimming ciliates. Also, rotifers tend to encyst or disappear if the loading is longer term.

In the SV30 test, an high loading increases turbidity before anything else happens. Turbidity is due to free bacterial cells in the solution.

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