Taste and Odor Concerns in Tap Water
Durham’s tap water remains safe for all drinking water purposes. While at times, the taste and/or odor of the water may be affected by temperature shifts and other seasonal changes, our tap water continues to meet all state and federal water quality standards. With the recent increase in water temperature, one of Durham’s two main water sources, Little River, experienced an increase in seasonal algae growth which can lead to odor/taste changes. To address this, Water Management staff has made some adjustments to our processes. We have tested Lake Michie’s water and it has not had the same level of algae bloom as Little River. For that reason, we’ll be using Lake Michie as our primary water source. Additionally, staff have begun adding Powder Activated Carbon at the Little River Reservoir. The combination of these two strategies should alleviate the taste and odor issues over the next several days.
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.