Course: BFM 203 Water Treatment and Control

Lecture

(2/9)

Physical Characteristics of Water

The physical characteristics of water (turbidity and color) relate to the sensory qualities of that water for domestic use. Turbidity is a measure of the cloudiness of water. The presence of suspended material such as clay, silt, finely divided organic material, plankton, or other organic material causes turbidity. Turbity is usually measured in terms of NTUs (Nephelometric Turbidity Units). The turbidity meter is an instrument used to measure the turbidity of liquids by passing light through them and determining the amount of light absorbed or reflected by particles in the liquid. Suspended materials above 5 NTU are usually visible and objectionable to users. The visual appearance of water with high NTU levels can be disturbing; in addition, suspended solids may harbor bacteria and create high chlorine demand. Finished water must be 0.3 NTUs or less.

Water color is impacted by dissolved organic material from decaying begetation and certain inorganic matter. Algal blooms, aquatic microorganisms, iron, manganese, and other substances may discolor water. As with turbidity, color is not only visually disturbing but may also be more than an aesthetic problem.

While the image to the right shows an unrealistic example of turbidity and color in drinking water, any visible turbidity and color is an indication of insufficiently treated water.