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Microscopy Guide

What you see, what it may indicate, and what process data to check next.

The microscope shows what the lab numbers cannot: floc structure, filaments and the higher life forms that reflect sludge age and process health.

Identify what I'm seeing

Answer a few questions about what is on the slide and get pointed to the likely match.
Stalked ciliates sketchBell-shaped ciliates on stalks attached to a floc particle, with a ring of cilia at the mouth.Line sketch for orientation only. Not to scale.

Stalked Ciliates

Bell shaped ciliates attached to floc by a stalk. Vorticella, Epistylis, Opercularia, Carchesium.

Free-swimming ciliates sketchOval cells covered in short cilia swimming in the liquid between flocs.Line sketch for orientation only. Not to scale.

Free-Swimming Ciliates

Ciliates that swim between flocs eating dispersed bacteria. Paramecium, Litonotus, Aspidisca (crawler).

Rotifer sketchA rotifer with a two-lobed crown of cilia, a body and a forked foot.Line sketch for orientation only. Not to scale.

Rotifers

Multicellular animals with a crown of cilia and a forked foot. A sign of older, stable sludge.

Amoeba sketchA naked amoeba with flowing pseudopods and a testate amoeba with a shell.testateLine sketch for orientation only. Not to scale.

Amoebae

Shape changing naked amoebae and shelled (testate) amoebae.

Flagellates sketchSmall oval cells each with a long whip-like flagellum.Line sketch for orientation only. Not to scale.

Flagellates

Small cells moving with one or more whip like flagella. Abundant in young sludge.

Nematode sketchA long smooth roundworm moving with a whip-like motion.Line sketch for orientation only. Not to scale.

Nematodes

Small, thrashing roundworms. Usually long SRT and stable conditions.

Filamentous organisms sketchLong filaments extending out of floc particles and bridging between them.Line sketch for orientation only. Not to scale.

Filamentous Organisms

Long chains of bacteria. A few support floc; too many cause bulking and foam.

Floc structure sketchA firm, rounded floc with dense center and a few short internal filaments.Line sketch for orientation only. Not to scale.

Floc Structure

Size, shape, strength and background clarity of activated sludge floc.

Dispersed growth sketchMany single bacteria and tiny clumps spread through the liquid with very little floc.Line sketch for orientation only. Not to scale.

Dispersed Growth

Bacteria growing as single cells or tiny clumps instead of floc. Cloudy effluent.

Photo gallery

53 photomicrographs from Brad Musick's slide collection: protozoa, higher life forms, filaments, floc and stains.

Illustrations

10 original drawings: protozoa groups, higher life forms, floc structure, bacterial shapes, capsules and sheaths, respiration.

Who dominates, and why

Graph of mass against time: food falls while amoebae, then flagellates (the stylized pink drawing on the second curve), free-swimming ciliates, stalked ciliates and finally rotifers rise and fall in turn; an arrow under the time axis shows that more wasting moves the sludge back toward the left
Relative predominance of organisms. As food is used up over time (longer sludge age, lower F/M), the dominant organisms shift from amoebae (first curve) and flagellates (second curve) to free-swimming ciliates, then stalked ciliates and finally rotifers. Wasting more sludge pushes the population back toward the left. What this indicates: Which group dominates your slide tells you roughly where the sludge sits on this curve. Many flagellates and amoebae mean a young, high F/M sludge; stalked ciliates and rotifers mean an older, low F/M sludge. Graphic: Brad Musick

The protozoa groups at a glance

Protozoa groupsSix panels: an amoeba with pseudopods, small flagellates with whip like flagella, an oval free-swimming ciliate covered in cilia, a crawling ciliate walking on floc, two bell shaped stalked ciliates on a floc, and a suctorian with knobbed tentacles on a stalk.The six protozoa groups operators trackAmoebaeFlowing pseudopods, slowYoung sludge, startupFlagellates5 to 20 microns, whip like tailYoung sludge, high soluble BODFree-swimming ciliatesCovered in cilia, fastYounger sludge, dispersed bacteriaCrawling ciliatesWalk on floc with cirriStable, well flocculated sludgeStalked ciliatesBells on stalks, ring of ciliaMature, stable sludgeSuctoriansTentacles catch other protozoaMature, older sludgeGreen text: what a large number of each group usually suggests. Line drawings, not to scale.
The six protozoa groups. Original line drawings of amoebae, flagellates, free-swimming, crawling and stalked ciliates and suctorians. What this indicates: Which group you see most of hints at sludge age: amoebae and flagellates for young sludge, crawling and stalked ciliates and suctorians for mature sludge. Original illustration for this site, not to scale.
The drawings are simplified sketches made for this site. Each organism page also has real photomicrographs from Brad Musick's slide collection. Learn the basics in Microscopy for operators and How do I read my microscope slide?