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Microscopy Illustrations

Original drawings made for this site to show what photos alone do not: the main organism groups, how floc is built, and what bacteria do with food and oxygen. Simplified and not to scale.

Protozoa | Higher life forms | Floc structure and settling | Bacteria

Protozoa

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.

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Naked and testate amoebaeLeft: a naked amoeba with pseudopods, nucleus, food vacuoles and a contractile vacuole. Right: two testate amoebae, a round brown Arcella shell and a vase shaped Euglypha shell made of plates, with pseudopods extending.Naked and testate (shelled) amoebaepseudopodnucleusfood vacuolescontractile vacuoleArcella (side view)EuglyphaNaked amoeba: young sludge, startup, recoverySlow, shape changing, easy to miss at 100xTestate amoebae: long SRT, low F/MOften with full nitrification
Naked and testate amoebae. A naked amoeba with pseudopods and vacuoles, and two shelled (testate) amoebae, Arcella and Euglypha. What this indicates: Many naked amoebae suggest a young sludge or a recovery from upset; testate amoebae suggest a long SRT, low F/M and often full nitrification. Original illustration for this site, not to scale.

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Flagellate size compared with flocA microscope field with a floc and five tiny flagellates around it, with one flagellate enlarged to show its oval body and whip like flagellum.Flagellates are tiny: look at 400x with phase contrastcell body 5 to 20 micronsflagellumDarts or spins; some are green (Euglena)about 100 micronsFloc in the view: 100 to 500 micronsA flagellate is a speck next to it at 100x
How small flagellates are. A 100x field with floc, and a 400x close up of one flagellate with its whip like flagellum. What this indicates: Flagellates are easy to miss at 100x. Large numbers at 400x point to high soluble BOD, a young sludge or low DO. Original illustration for this site, not to scale.

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Higher life forms

Higher life formsFour panels: a rotifer with a two lobed ciliated crown and forked foot, a smooth nematode worm, a segmented Aeolosoma bristle worm with bristle tufts and colored spots, and a water bear with eight clawed legs.Higher life forms in activated sludgeRotifer100 to 500 micronsCiliated crown, forked footNematode0.5 to 3 mmSmooth roundworm, thrashesBristle wormAeolosoma, up to 10 mmSegments, bristle tufts, color spotsWater bearTardigrade, 0.1 to 1 mmEight stubby clawed legsAll are multicellular and usually point to an older, stable sludge with a longer SRT.
Higher life forms. Rotifer, nematode, bristle worm (Aeolosoma) and water bear (tardigrade), with typical sizes. What this indicates: These multicellular animals grow slowly, so steady numbers usually mean a long SRT and a stable, well oxidized sludge. Original illustration for this site, not to scale.

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Floc structure and settling

Inside a healthy flocAn irregular floc made of floc forming rod bacteria held together by sticky polymer, with a few short filaments running through it as a backbone, some trapped particles and stalked ciliates on its edge. The liquid around it is clear.Inside a healthy flocFilament backbone gives strengthFloc forming bacteria (mostly rods)EPS: sticky polymer glueTrapped particles and finesStalked ciliates graze on the edgeClear liquid, few dispersed cellsSize: about 50 to 1,000 micronsFirm, irregular, a few internal filaments, clear background: settles well and leaves a clear supernatant.
Inside a healthy floc. Floc forming rods held in sticky EPS around a short filament backbone, with trapped particles and stalked ciliates on the edge. What this indicates: Firm, irregular floc with a few internal filaments and a clear background settles well and leaves a clear supernatant. Original illustration for this site, not to scale.

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Healthy floc, filamentous bulking and pin floc comparedThree microscope views with settleometers: healthy floc with a few internal filaments settles well with a clear supernatant; filamentous bulking with filaments bridging flocs settles slowly to a high blanket; pin floc of tiny particles settles fast but leaves a turbid supernatant.Three floc conditions comparedHealthy flocFilamentous bulkingPin flocSettles well, clear supernatantSVI usually 80 to 150Filaments mostly inside flocSettles slowly, compacts poorlyHigh SVI, blanket may riseFilaments bridge between flocsSettles fast, turbid supernatantLow SVI, cloudy effluentFew or no filaments, long SRTDrawings show a 100x view and a 30 minute settleometer for each case. Not to scale.
Healthy floc, bulking and pin floc. Three 100x views, each with its 30 minute settleometer result. What this indicates: Filaments bridging flocs mean high SVI and slow settling; tiny, filament free pin floc settles fast but leaves a cloudy supernatant, often from too long an SRT. Original illustration for this site, not to scale.

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Dispersed growth compared with healthy flocLeft: a firm floc in clear liquid with a stalked ciliate, and a settleometer with a clear supernatant. Right: many single bacteria and tiny clumps with a free-swimming ciliate and a flagellate, and a settleometer that stays cloudy.Dispersed growth compared with healthy floc30 min30 minHealthy flocFirm floc, clear liquid, stalked ciliatesClear supernatantDispersed growthSingle cells and tiny clumps, free swimmers and flagellatesCloudy supernatant that does not clear
Dispersed growth compared with healthy floc. A healthy floc field next to a field full of single cells and tiny clumps, with their settleometers. What this indicates: Dispersed growth points to a very young sludge, toxicity, high load or low DO. Expect turbid effluent until floc reforms. Original illustration for this site, not to scale.

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Bacteria

Bacterial shapesThree microscope fields: round cocci as singles, pairs, chains, clusters and tetrads; rod shaped bacilli single and in chains; and spiral shaped bacteria including a comma shaped vibrio.Bacterial shapes seen at 1000xtetradsingle, pairchainclusterrods in a chainvibrioCoccus (round)Singles, pairs, chains, clusters, tetradsBacillus (rod)Most floc formers are rodsSpiralSpirillum, and the comma shaped vibrioMost bacteria are 0.5 to 3 microns, too small to see well below 400x.
Bacterial shapes. Cocci (singles, pairs, chains, clusters, tetrads), bacilli (rods) and spirals at 1000x. What this indicates: Shape alone does not identify a bacterium, but it is the first step in reading a Gram stain, and tetrads in large numbers can point to high organic acids. Original illustration for this site, not to scale.

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Capsules and sheathsLeft: rod shaped bacteria each surrounded by a clear capsule of slime. Right: a sheathed filament with cells inside a clear tube, a false branch and an empty section of sheath.How bacteria protect themselves: capsules and sheathscapsulecellempty sheathfalse branchcells inside a sheathCapsule (slime layer)Shows as a clear halo in India inkSheathA clear tube around a filament, as in S. natans
Capsules and sheaths. Bacteria with slime capsules (clear halos in India ink) and a sheathed filament with cells inside, an empty section and a false branch. What this indicates: Heavy capsule (slime) formation can cause viscous bulking, often from nutrient deficiency; a sheath and false branching help identify filaments such as S. natans. Original illustration for this site, not to scale.

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Aerobic respirationOrganic food and dissolved oxygen enter a bacterium. It produces carbon dioxide, water, new cells and energy.Aerobic respiration: what a floc forming bacterium does with food and oxygenBacteriumoxidizes the foodOrganicsBOD (food)O2Oxygen from aerationCO2carbon dioxideH2OwaterNew cellssludge growth (WAS)Energypowers the cellOrganics + O2 → CO2 + H2O + new cells + energy
Aerobic respiration. Bacteria use food (organics) and oxygen to make carbon dioxide, water, new cells and energy. What this indicates: This is why oxygen demand rises with load, and why the new cells must be wasted to hold a steady sludge age. Original illustration for this site, not to scale.

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For real examples, see the photo gallery or start with Identify what I'm seeing.