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Spring runoff refers to the high water flows encountered when warmer temperatures cause snow in the watershed to melt. This can cause higher than normal stream flows and flooding in low-lying areas. This melt-water will carry with it dead and decaying organic material such as leaves and grasses, as well as mud and silt that is stirred up by increased stream flows.
Color - Some of this organic material will stain the water brown, similar to the action of tea leaves. This stain in the water is referred to as color. The treatment process removes most of the color. However, in conditions where the level of color is very high, some of the color may be carried into the finished water. Consumers may notice a slight discoloration in the water when filling white sinks or tubs. Color in the water can contribute to the musty or earthy tastes that are associated with spring runoff.
Chlorine in the Spring - When water quality in the Red Deer River deteriorates, due to the annual runoff or from heavy rainfall or flooding events, higher doses of treatment chemicals, including chlorine, are required to clean the water.
After the treatment process is completed, a small amount of un-reacted chlorine, called residual chlorine, remains present in the water supply to protect against bacterial contamination in water mains, water storage tanks and in household plumbing. The amount of residual chlorine in the water leaving the water treatment plant is constant and is usually not detected by the consumer except in spring runoff when last years dead leaves and grasses have decayed and are carried into the river by snowmelt. Organic material from this surface runoff is difficult to completely remove from the water and while harmless, the small amount remaining can react with the residual chlorine and may impart an unpleasant musty/chlorine odor to the water. The consumer can conclude this to mean that if they can smell chlorine in the water, the City must have increased the dose. The City will have increased the dose in the treatment process, but the amount of residual chlorine in the finished water supply is actually still the same as it was before. It only becomes more noticeable when certain dissolved organics are also present.
Chlorine is the most common disinfectant used in the treatment of public water supplies because it is extremely effective in destroying harmful bacteria and because residual chlorine levels can be easily detected and measured. Bacteria cannot survive in a chlorine environment so the presence of residual chlorine is a key indicator of water quality. Residual chlorine levels in public water supplies in Alberta are regulated by Alberta Environment and are closely monitored at the water treatment plant and in the public distribution system.
Q. Is the water safe to drink?
Yes. The water that leaves the Red Deer Water Treatment Plant meets and exceeds all of the standards contained in the “Guidelines for Canadian Drinking Water Quality.” The water is safe for all to use and enjoy.
Q. Why does the water taste and smell different?
The City of Red Deer uses a surface water supply, (Red Deer River) as a source of drinking water for its residents. All surface water supplies such as ours are susceptible to high turbidity and high organic loading during the annual spring snowmelt and runoff. These conditions can give the raw water a disagreeable odor and taste. The treatment process removes most of these tastes and odors, however enough may remain after treatment to be noticeable to the consumer. The treated water at the tap is still completely safe to drink.
Q. What chemicals does the City use to treat the drinking water in the spring?
Aluminum salts are used to coagulate or “stick together” particles in the water. Fine sand and polymer are also added to help weight the coagulated particles and make them easier to remove by settling. Because the levels of organic material in the river water are higher during spring runoff, coagulant doses are also increased to remove organic color.
Potassium permanganate is used in the spring to help oxidize some of the organic in the raw water.
Powdered activated carbon is also used in the spring to help remove some of the taste and odor causing compounds. Carbon works through a process known as adsorption. Particles in the water will adhere or stick to the surface of the carbon grain.
Chlorine is used as a disinfectant in the water treatment process year round. Because of the high levels of organic present during the runoff, the amount of chlorine in the springtime is greater than that used at other times of the year. This additional chlorine is used up by the organic in the raw water. The amount of chlorine in the tap water is the same year round. The tap water may have a slight chlorine smell in spring conditions, due to organic, which have combined chemically with chlorine.
Q. How long will the taste and smell last?
Each spring is different, but on average, runoff conditions will last for between three and six weeks. Mountain runoff in late June and early July, can also cause runoff conditions, if accompanied by heavy rainfall in the watershed.
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