Turbidity Measurement Units Explained

Turbidity is a measure of the cloudiness or haziness in a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air.

In water quality analysis, turbidity is measured using specific units. Let's look at the common units and identify the one not typically used:

Standard Turbidity Units

• NTU (Nephelometric Turbidity Units): This is the most widely used unit for measuring turbidity. It is based on the principle of nephelometry, which measures the amount of light scattered by particles suspended in the water.
• JTU (Jackson Turbidity Units): An older unit of turbidity measurement. It is based on the Jackson turbidimeter, which measures the depth (in inches) of a suspension required to obscure a standard candle flame viewed through the liquid. 1 JTU is approximately equal to 1000 NTU, but it's less common now due to its reliance on visual standards and subjectivity.
• FTU (Formazin Turbidity Units): This unit is closely related to NTU and is also based on the Formazin polymer standard, which was developed to provide a more stable and reproducible turbidity standard. In practice, FTU and NTU are often used interchangeably.

Non-Standard Turbidity Unit

• ATU: While units like NTU, JTU, and FTU are standard measures for turbidity, ATU is not a recognized or standard unit for quantifying the turbidity of water. The abbreviation ATU might refer to other concepts in different scientific fields (like Activity Time Unit), but it is not associated with turbidity measurement in water analysis.

Therefore, ATU is the unit not used to measure the turbidity of water among the given options.