Drinking Water

Drinking water is one of the easiest things in the world to take for granted. We turn the tap and out comes clean and fresh, life-sustaining water. Most people don't realize just how much planning, design and work goes into delivering water to their home. Providing an adequate water supply for a community includes three things: 1) finding and developing an adequate water source; 2) treating the water to insure that it is clean enough to drink; and 3) delivering the water to every residential, commercial and industrial building within the service area.

Finding and Developing a Water Source

In Utah, as with most parts of the world, there are two types of water sources: ground water and surface water. In some parts of the world, other water sources have been developed. Rainwater can be collected where precipitation rates are high enough. In extremely arid regions bordering the ocean, desalination (salt removal) of seawater is an expensive alternative that is becoming more common. In Utah, however, drinking water supplies come from either surface or ground water sources. Of course both of these sources are fed by precipitation. It is primarily the snow in our mountains during the winter months that recharge the ground water aquifers and fill up our streams, rivers, lakes and reservoirs.

Ground water is extracted from an aquifer by the use of wells. While ground water taken from different locations can have vastly different water quality characteristics, generally ground water is much cleaner than surface water. Surface water tends to pick up natural and man-made pollutants. As water moves through the ground, many of these pollutants are filtered out. Consequently, ground water usually requires less treatment and is cheaper to process to drinking water standards

Surface water sources include: rivers, streams, lakes, reservoirs and even springs. A spring is a location where ground water comes to the surface. Consequently, the classification of a spring as surface water or ground water depends upon the definition. For a long time springs were considered to be ground water sources and treated as such. The close proximity with the ground surface, however, makes a spring very susceptible to the same pollutants that can contaminate surface water sources. Consequently, springs are now considered surface water sources by governmental regulatory agencies and the treatment of spring water is held to the same strict standard as other surface water sources.

Water Treatment

Water taken from a surface or ground water source is referred to as "raw" water to distinguish it from treated or "finished" water. Raw water is treated not just to remove disease-causing organisms but also to remove silt, grit and humus material (suspended solids), which can have a detrimental affect upon pipes, meters and other components of the water distribution system. Treating raw water also improves the taste and eliminates objectionable odors or color

The cleaner and better the quality of the raw water, the easier and cheaper it is to treat. Consequently, federal, state and local government agencies have developed plans and laws that protect and preserve the quality of drinking water sources. Many surface water streams along the Wasatch front are important sources of drinking water, but also double as recreation areas. Since we camp and picnic in the watersheds and boat, fish and water-ski on the very water we drink, it is important that we are responsible about litter control, use of public restrooms and safeguarding against fires to minimize the impact upon a critical drinking water source

The water treatment process can range from a simple filter or chlorination, to a complex treatment plant. A small rural community drinking water system, with a high quality ground water source, may need very little, if any, treatment. For much larger public water systems, particularly when the water source is subjected to repeated human contact such as heavy recreational use, the treatment process is much more complicated and will likely include a combination of the following processes

Initial Filtration - Often the initial step is to filter the water through some course screens to remove any fish, bugs, leaves, twigs, and debris.

Coagulation & Sedimentation - Alum and lime are added to the water. These chemicals then bond with suspended sediments, bacteria and fine particles present in the water to form a sticky floc, which looks like white foam or suds on the water. Over time and as the water is stirred slightly all the fine particulate matter is bonded to the floc, which eventually becomes heavy and sinks to the bottom of the tank.

Disinfection - This is the controlled addition of some germ-killing chemical, usually chlorine, to the water. This treatment step can take place early, late or even repeatedly in the water treatment process. Often it is a final step.

Aeration - Taste and odor problems are often a result of the presence of dissolved gas such as natural occurring hydrogen sulfide, or living organic material such as algae, or decaying organic material, industrial waste or even residual chlorine. Forcing tiny bubbles of air through the water facilitates the release of these gases from solution reducing unpleasant odors and taste.

Water Deliver and Distribution

Once water has been treated, it is ready for distribution to homes and businesses. There is, however, a logistics problem between treatment and delivery. While treatment plants are designed to treat water at a constant rate, people don't use water at a constant rate. Traditionally there is less water use during the late night and early morning hours than during the day. Daily water use tends to peak in the morning as people prepare for their day, and then again in the evening as people return home to prepare dinner. In the summertime lawn watering can also dramatically impact the peaking nature of water use. Consequently, it is important to have enough storage capacity within the distribution system to meet the days peaking requirements without running out of water. Pipes that deliver the water from the storage tank to the individual homes and businesses also have to be sized large enough to convey water during the times of peak usage. Fire-fighting imposes even greater demands upon the system, requiring that pipes and storage reservoirs be sized large enough to battle a blaze during periods of peak water use without losing water pressure or depleting

Insuring adequate water pressure throughout the system is yet another problem for water system designers. Smaller pipes cost less to purchase and install than large pipes. But to deliver the same amount of water through a smaller pipe means that the water must travel faster. Since there is an interdependent relationship between the velocity of the water and the pressure in the pipe, the designer must size pipes large enough to accommodate the required flow without increasing the project cost by over-sizing pipes.