Turbidity Meter

How to measure Turbidity?

There are several ways to measure turbidity, depending on the level of accuracy needed and the available equipment.

1. Nephelometric Turbidity Units (NTU) – Turbidity Meters

• The most widely used method for assessing turbidity in water.
• Utilizes a turbidimeter (nephelometer) to project light through the sample and measure how much is scattered at a 90-degree angle.
• Readings are provided in Nephelometric Turbidity Units (NTU).

2. Secchi Disk (For Large Water Bodies)

• A simple, manual method often applied in lakes and oceans.
• Involves lowering a black-and-white disk into the water until it is no longer visible.
• The disappearance depth is recorded as an indicator of water transparency.
• While less precise than NTU meters, it is effective for monitoring long-term water clarity changes.

3. Jackson Turbidity Unit (JTU) – Jackson Candle Method

• An older approach to measuring turbidity, historically used before NTU meters.
• A glass tube is placed over a lit candle, and water is added gradually until the flame is no longer visible.
• The corresponding depth is expressed in Jackson Turbidity Units (JTU).
• This method has largely been replaced by more modern nephelometric techniques.

4. Formazin Turbidity Standard (FTU/FNU)

• Uses formazin polymer as a standardized reference material for calibration.
• Readings are reported in Formazin Nephelometric Units (FNU) or Formazin Turbidity Units (FTU), depending on the specific measurement technique.
• Commonly applied in laboratory research and regulatory settings.

5. Gravimetric Analysis (Total Suspended Solids – TSS)

• Measures the actual mass of suspended particles by filtering a water sample and weighing the collected residue.
• More precise for quantifying solid content but does not directly determine turbidity in NTU or other optical units.