Run protocol
One session, start to finish. Split it across two days and the light changes, which invalidates the calibration.
Synthetic greywater
Stock, 5 litres. Enough for a calibration series and three column charges.
| Component | Quantity | Purpose |
|---|---|---|
| Tap water | 5 L | — |
| Fine soil, sieved | 15 g | suspended solids |
| Neutral liquid soap | 5 ml | surfactant load |
| Blue food colouring | 20 drops | adsorption tracer |
Stir again immediately before drawing every sample. Solids settle in minutes, and settled stock reads as clean water.
Check this before going further
With the jar full of undiluted stock, the target card behind it must still be faintly visible. If it disappears completely the contrast measurement saturates and the calibration is worthless. Too opaque, add water; too clear, add soil 5 g at a time.
Grading the scoria
Laboratory sieves give the cleanest result but are not required. Whatever the method, report it plainly and give numbers actually measured rather than a nominal mesh size.
| Method | What to report |
|---|---|
| Laboratory sieves | D10 and uniformity coefficient |
| Kitchen or insect mesh | Aperture measured by counting wires per centimetre |
| Sedimentation | Settling times and mass recovered per fraction |
Sedimentation needs no equipment at all: crush the scoria, shake it in a tall bottle of water and let it settle. Coarse grains reach the bottom first and fines last, so decanting at timed intervals separates the fractions. It is settling-velocity separation, the same principle as the hydrometer analysis used in soil mechanics.
Calibration series
Five levels, 200 ml each.
| Sample | Stock | Clean water |
|---|---|---|
| cal0 | 0 ml | 200 ml |
| cal1 | 50 ml | 150 ml |
| cal2 | 100 ml | 100 ml |
| cal3 | 150 ml | 50 ml |
| cal4 | 200 ml | 0 ml |
Photograph each in the same jar, washing and drying it between levels.
The run
- 01
Photograph the influent
Stir the stock, fill the jar, shoot it as
influent. - 02
Charge the column
Close the valve and pour 884 ml of stock in at the top.
- 03
Open the valve and start the timer
Collect the effluent in the measuring jug.
- 04
Record the flow rate
Time how long 500 ml takes to pass.
- 05
Photograph the effluent
Same jar, same fill level, same position.
- 06
Repeat, at least three charges
The first charge reads best and removal drops as the bed loads. That curve is the useful result, not the single first number.
What to write down at the time
- Depth and volume of each medium as placed, and the graded yield from the raw scoria
- The grading method and its measured aperture or settling times
- The greywater recipe actually used, not the one planned
- Flow rate and removal percentage per charge
- Room temperature
Photograph the build at every stage, including the versions that did not work, the graded fractions side by side, the five calibration jars as a gradient, and influent next to effluent.