Turbidity
Frequently Asked Questions
Turbidity Ratings
Good (<1 NTU) - It is recommended that newborns and people with compromised immune systems drink boiled water or a safe alternative.
Fair (1-5 NTU) - It is recommended that children, the elderly, people with compromised immune systems and anyone seeking additional protection drink boiled water or a safe alternative.
Poor (>5 NTU) - It is recommended that all users drink boiled water or a safe alternative. Tap water intended for drinking should be brought to a rolling boil for at least one minute.
What is turbidity?
Turbidity is a water quality term that refers to fine suspended particles of clay, silt, organic and inorganic matter, plankton and other microscopic organisms that are picked up by water as it passes through a watershed.
Which water sources are most affected by turbidity?
Turbidity levels are much higher in water from surface water sources (e.g. streams, rivers, and lakes) than from groundwater sources. Some surface water sources exhibit high turbidity levels during periods of high precipitation or snow melt (e.g. spring runoff).
City of Kelowna's Water Utility
Okanagan Lake is the water source for the City of Kelowna's water utility. Rarely does the utilitiy's turbidity level go above 1 NTU. Trained technicians perform more than 5,000 individual water quality tests each month on source water and water in the distribution system. Source water is monitored 24 hours a day using computerized sampling equipment. Any significant change in pH, turbidity or temperature triggers a deviation response plan that includes further detailed testing and customer notification.
The City installed UV reactors at three lake intakes in 2005 to enhance the primary chlorine disinfection. Ultraviolet light treatment has been found to be effective in inactivating certain parasites such as giardia and cryptosporidium that can be present in source water. For more information on the City's source-to-tap approach, click on water quality.
How is turbidity measured and reported?
Turbidity, which is measured and reported in nephelometric turbidity units (NTU), is an optical measurement of water’s ability to scatter and absorb light rather than transmit it in straight lines. Turbidity levels can range from less than 1 NTU to more than 1,000 NTU. At 5 NTU water is visible cloudy; at 25 NTU it is murky.
How often is my water tested, and for what?
Water intended for drinking is measured against physical, chemical, radiological and microbiological standards outlined in the federal Guidelines for Canadian Drinking Water Quality. To that end, your water is tested regularly for viruses, bacteria (e.g. e-coli), parasites (e.g. giardia and cryptosporidium), and turbidity. The guidelines recommend that water intended for drinking have a turbidity level < 1 NTU.
The City of Kelowna has online turbidity monitoring 24 hours a day, 7 days a week. In addition, City of Kelowna Water Quality staff collects samples daily to confirm the online turbidity data.
How will elevated levels of turbidity be reported?
In keeping with the Guidelines for Canadian Drinking Water Quality and B.C.’s Drinking Water Protection Act, water suppliers will notify customers of turbidity levels that exceed 1 NTU. A turbidity index on the supplier’s website will indicate if the water is ‘Good’ (<1 NTU), ‘Fair’ (1-5 NTU), or ‘Poor’ (>5 NTU), and provide recommendations for each. ‘Fair’ and ‘Poor’ ratings will also be publicized through the media.
Why is turbidity an important water quality indicator?
Bacteria, viruses and parasites such as giardia and cryptosporidium can attach themselves to the suspended particles in turbid water. These particles then interfere with disinfection by shielding contaminants from the disinfectant (e.g. chlorine). Chlorine is not effective in deactivating cryptosporidium.
For more information regarding health issues related to turbidity contact the Interior Health Authority at: (250) 862-4200 or visit www.interiorhealth.ca.
