Turbidity in Drinking Water Information:

Properties:

Turbidity measurements are used to determine how clear and clean a water sample is. Small particles like clay, silt, algae, and microorganisms can be suspended in water and cause light scattering, giving water a milky or cloudy appearance.1 With an instrument called a nephometer, the amount of light scattered by particulate matter is measured in units of Nephelometric Turbidity Units (NTU).1 Completely clear water has a value below 1 NTU; slightly milky water has measurements around 5 NTU; any values above 60 NTU would make water extremely difficult to see through in a glass (Clare Co. What’s in your water?).

Sources:

There are many sources of turbidity in drinking water; heavy rainfall or disturbances to land near raw water sources can increase the concentration of organic particulates, and faecal contamination from sewers or farms can increase the concentration of bacteria and microorganisms.1 High levels of turbidity can also affect disinfection systems and prevent pathogen removal during treatment.2

Regulations:

Levels of turbidity in drinking water must be acceptable to consumers and may not undergo abnormal changes.

Health/Environmental Concerns:

Turbidity itself is not a cause for concern; however, when bacteria, viruses, or parasites such as Cryptosporidium persist in turbid water, consumers may become sick and experience adverse health effects.1 High levels of organic matter can also compromise disinfection systems by allowing microorganisms and bacteria to survive or by reacting with chlorine compounds to form THM’s (carcinogenic by-products).

Action:

If water does appear cloudy and turbidity levels are elevated, it is important that water treatment processes such as filtration and disinfection are adjusted properly. Additionally, action may be required if water quality drops below the acceptable standards for consumers. If you suspect that your drinking water supply is contaminated, contact your Water Service Authority. If drinking water makes you feel ill, contact a doctor right away.

1 Guide to the Parameters in the European Communities. What’s in your water?; S. I. No. 278 of 2007; National Federation of Group Water Schemes: Ireland.

 2 Water Quality and Health Review of Turbidity. Information for Regulators and Water Suppliers Technical Brief; License CC BY-NC-SA 3.0 IGO. World Health Organization, 2017.