Settling Test
Getting started
New to this tool? Switch on Worked example at the top of this tab. It loads a set of readings so you can see how the test works; switch it off to get your own entries back.
Settling Test is the whole of the tool. Work down it: the test instructions, who and when, the samples, the cylinder, the readings, then what you can see. The clarifier details are optional, but they are what turn a settling velocity into an answer. Records keeps dated snapshots and draws the trend; Report & Save is the only place anything leaves the tool.
About this model, top right, explains how the numbers are worked out and what the result colours mean. Settings holds the ranges every result is judged against.
- Take the sample from the settling zone of the clarifier. A blanket sample tap is the easiest way if the clarifier has them; otherwise a sampling tube or a jar on a pole. Fill it in one go and take it straight to the cylinder.
- If the clarifier has taps at several heights, run them together. Fill a cylinder from each, start them at the same moment and read them at the same times. Three cylinders side by side tell you how the blanket is layered, which one sample never can.
- If you are using a tap, flush it first. Run it until what comes out matches what is in the clarifier, then fill the cylinder. Open it wide rather than cracking it: a nearly shut valve shears floc apart and you will measure the damage instead of the sludge.
- Fill the cylinder to the top graduation and start the timer as you set it down.
- Leave it still and out of the sun, at about the temperature of the clarifier. Do not stir it or tap it.
- Read the graduation the interface sits on — the line where cloudy sludge below meets clearer water above — at each of the times below. Write down the millilitre number.
- At each reading, note what the interface and the water above it look like. Those two change through the test and they tell you as much as the numbers.
- Read often in the first few minutes. That is the part the settling velocity comes from; the later readings show how far it compacts.
| Sample | Depth below the surface (m) | Solids |
|---|
Enter these and the tool compares the settling velocity against the rate the water is rising through the clarifier. That comparison is what the test is really for.
This is the interface falling down the cylinder. The steeper the line, the faster the sludge is settling. The shaded stretch is the straight run the velocity was taken from; the flattening towards the end is compaction, which is a different process and is not used. Hover or tap any point for what was measured there.
Saving takes a dated snapshot of the results above. It does not change anything on this tab, and you can carry on editing afterwards. Saved tests are listed on the Records tab, where the trend is drawn.
Records
Guide: using this tab
One test tells you about today. A run of them tells you whether the floc is getting lighter, whether a dose change did anything, and how much margin the clarifier loses as the water cools.
Tests are saved from the bottom of the Settling Test tab. This tab lists what has been saved and draws the trend.
Save a record even when everything looks normal. A good day is what you need to compare a bad day against, and nobody ever has enough of them written down.
Report & Save
Guide: using this tab
Everything leaves the tool from here and nowhere else.
- PDF prints what you tick below, with every value written out as text so nothing comes out blank.
- CSV gives you the readings and results as a spreadsheet.
- Save writes a file holding everything, including records and settings. Load it back later on any machine.
Nothing is uploaded anywhere. The tool runs entirely in your browser and files go to your own downloads folder.
In the print dialogue, turn headers and footers off and leave background graphics on.