Method | advantage | disadvantage |
Jackson Candle Turbid meter -Water poured into tube. -Reading taken when candle burning under tube can no longer be seen. | (Historical method.) | No longer a standard method. Can’t measure < 25 JTU (25 NTU). |
Turbid meter (Nephelometer) -Beam of light passed through water sample. -Amount of light scattered at a 90˚ angle measured. | Extremely accurate. Some are portable. Can measure very low turbidity. | Expensive. Easily damaged. Requires power source. Requires calibration. |
Secchi Disk -Black and white disk lowered into water. -Maximum distance at which disk can be seen recorded. | Low cost. Portable. No consumables. Easy to learn | Less accurate. Can’t be used in shallow water or swift currents. Not applicable to small sample size. |
Turbidity Tube (Transparency Tube) -Combination of Jackson candle and Secchi disk methods. | Low cost. Portable. No consumables. Easy to learn. Suitable for all water sources. | Less accurate. Can’t measure < 5 NTU. |