Odor & Taste Concerns in Tap Water
Durham’s tap water is safe to use for all drinking water purposes. At times, the odor and/or taste of the water may be affected by temperature shifts and other seasonal changes. With the recent increase in water temperature, Durham’s main water sources – Lake Michie and Little River – experienced an increase in algae growth that cause odor/taste changes. To address this, Water Management staff adjusted dosages of copper sulfate – a chemical widely used in the water treatment industry for taste and odor control. Additionally, crews were dispatched to flush portions of the distribution system. Our staff seasonally tests Durham’s source waters, as well as our terminal reservoirs, to look for any excess growth of algae. Staff also regularly tests more than 150 sites throughout the City’s distribution system, monitoring chlorine levels and other drinking water parameters.
Customers with concerns about their tap water quality are encouraged to contact Durham One Call at 919-560-1200, https://durhamnc.gov/onecall, or via its mobile app. More information is also available in our annual Water Quality Report; the latest version is published online here.
Algae are a natural and important part of lake and reservoir ecosystems. The term “algae” refers to a wide variety of different organisms that use light to grow. Depending on the species, algae can live in fresh or salt water. Freshwater algae, also called phytoplankton, vary in shape and color. They are found in a large range of habitats, such as ponds, lakes, reservoirs, and streams. Algae are the base of the aquatic food chain in these habitats. Small aquatic animals eat the phytoplankton and are then eaten by larger animals.
Under certain conditions, several species of true algae as well as cyanobacteria can multiply and cause changes to the fresh water. These changes do not affect the safety of our drinking water, but can include excess foam and scum, a slight change in the color of the water, as well as taste and odor problems. These are known as algal blooms, and occur when the numbers of algae in a body of water increase rapidly. Lakes, ponds, and slow-moving rivers are most prone to blooms. Algal blooms are natural, and may occur regularly (e.g., every spring). This depends on weather and water conditions during a particular season. The likelihood of a bloom depends on local conditions and characteristics of the particular body of water.
Algal blooms generally occur during warm, sunny, calm conditions in water where nutrient levels are high. Aquatic ecologists are concerned with blooms of algae in reservoirs, lakes, and streams because they can have ecological, aesthetic, and human health impacts. In waterbodies used for water supply, algal blooms can cause physical problems (e.g., clogging screens or filters) and odor and/or taste problems, as we have experienced recently here in Durham.
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