What is turbidity?

by wfnblog on May 16, 2012


Frequently Asked Water Filter Questions Answered

Raise your glass of water and hold it up to the light. Does the water seem hazy? If so, the water is turbid. Your water lacks its inherent clarity or brilliance.

Turbidity describes how cloudy or clear your water is. It is a key factor in evaluating water quality. Turbidity is measured in terms of the amount of light scattered and absorbed by the suspended matter in the water. The more total suspended solids (TDS) in the water, the murkier it seems and the higher the turbidity. The particles may range among many different sizes. While some suspended material will be large and heavy enough to settle rapidly to the bottom of the container if a liquid sample is left to stand, very small particles will settle only very slowly or not at all. Generally, the cloudy appearance of turbid water is caused by microscopic particles you cannot see, similar to smoke in the air. Turbidity in water involves various forms of suspended matter: clay, silt, organic and inorganic matter, and microbial organisms.

Turbidity indicates drinking water qualityTurbidity in open water may be caused by plankton growth. On land, construction projects disturb the natural terrain, leading to high sediment levels entering water bodies during rain storms. Urbanized areas also contribute large amounts of turbidity to nearby waters, through storm water runoff pollution from paved surfaces such as roads and parking lots. Certain industries such as coal mining can also generate very high levels of turbidity from rock particles that get suspended in groundwater.

When water has a large amount of these suspended particles, it quickly loses its natural appeal. While it may be safe to drink, it is likely to seem offensive to taste, touch, sight or smell.

Turbidity, however, is more than simply an aesthetic issue. It is critical to successful water treatment and disinfection to keep turbidity levels low. Higher turbidity levels are often linked with higher levels of disease-causing microorganisms such as certain parasites, viruses, bacteria and cysts. In drinking water, the higher the turbidity level, the higher the risk that people may develop gastrointestinal diseases. This is especially problematic for immunocompromised people, because contaminants like viruses or bacteria can become attached to the suspended solid. The suspended solids interfere with water disinfection by chlorine, because the particles act as shields for viruses and bacteria. Similarly, suspended solids can protect microorganisms from ultraviolet (UV) sterilization of water.

Fortunately, reducing turbidity in your drinking water supply is a straightforward process. The Water Quality Association (WQA) recommends treating turbid water with an activated carbon filter and/or particulate filter.

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