Understanding Turbidity in Water Quality

Study Notes

Turbidity measures water clarity, specifically the light scattering caused by suspended particles.
Larger and more surface-active particles scatter more light, resulting in higher turbidity.
Sources of turbidity include soil erosion, vegetable fibers, microorganisms, and emulsifying agents like soap and detergents.
High turbidity negatively impacts water treatment, reduces light penetration in water bodies, and provides habitats for pathogens.
Turbidity measurements are conducted using a nephelometer or turbidimeter, which measures light scattered at 90 degrees.
Turbidity units are typically measured in Nephelometric Turbidity Units (NTU), Formazin Turbidity Units (FTU), or Formazin Nephelometric Units (FNU).
The Jackson Turbidity Unit (JTU) was previously common but is no longer standard.
In lakes, turbidity can be assessed using a Secchi disk, which measures the depth at which it disappears from view.
Turbidity measurements can be used to estimate Total Suspended Solids (TSS) concentration.
Desirable drinking water turbidity levels are typically below 1 NTU, with many utilities aiming for 0.1 NTU or lower.
European standards specify a maximum turbidity of 4 NTU, while the World Health Organization recommends a maximum of 5 NTU.

Naturally occurring water is generally colorless, but dissolved organic materials, like algae, fungi, and bacteria, can give it a noticeable color.
Color is measured with a tintometer, which compares the water sample with a standard solution, using Hazen units.
A Hazen unit is equivalent to the color produced by 1 ppm platinum as chloroplatinic acid with 2 ppm cobalt chloride.
Colour can also be measured using absorbance values (optical density) across the visible spectrum, with a peak at 500 nm indicating red coloration.
Samples are typically filtered through a 0.45 mm filter before measuring color to remove suspended particles.
Colored water can create problems in wet processing, such as dyeing and finishing in textiles.