Thermo Scientific Orion AQUAfast AQ3010 Turbidity Meter User Guide
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Appendix 1
Turbidity Theory
Turbidity is defined as an “expression of the optical property that causes
light to be scattered and absorbed rather than transmitted in straight lines
through the sample .” That is, turbidity is the measure of relative sample
clarity, not color .
Water with cloudy or opaque appearance will have high turbidity, while
water that is clear or translucent will have low turbidity . High turbidity
value is caused by particles such as silt, clay, microorganisms and organic
matter . By definition, turbidity is not a direct measure of these particles
but rather a measure of how these particles scatter light .
For drinking water applications, a turbidity value may give an indication
of presence of bacteria, pathogens or particles that can shelter harmful
organisms from disinfection process . Therefore, turbidity measurement
is particularly useful for water treatment plants to ensure cleanliness . For
wastewater effluent testing, turbidity is often required to ensure that the
released effluent will not harm the environment .
In industrial processes, turbidity can be part of quality control measure to
ensure efficiency in treatment or manufacturing process .
There are two internationally accepted standard specifications for
turbidity measurement . These are the international standard ISO 7027
and the US EPA method 180 .1 .
Basically the ISO 7027 is a more stringent standard and requires the use
of a monochromatic light source . It also governs the design of a turbidity
meter in the following areas: (1) Light source’s wavelength; (2) Light
sources’ spectral bandwidth; (3) Measuring angle; (4) Aperture angle in
water sample; (5) Distance traversed by incident light and scattered light
within the sample and (6) Calibration standard .
The AQ3010 turbidity meter follows the ISO 7027 standard whose
specification allows for greater reproducibility of the measured values and
greater agreement between other measuring instruments .
Definition
Why s t
mportant?
Measurement
Principle
