Water Treatment Process
-
Tulsa's main water sources are Lake Eucha, Lake Spavinav, and Lake Oologah. Water is brought from the lake through two pipes called flowlines that are 53.9 miles and 52.2 miles long. Each flowline is made from concrete up to 8 inches thick, and are 41/2 to 6 feet deep.
-
Water is drawn from the lake by these flowlines and is pumped to the water treatment plants through the use of raw pump stations.
-
Upon entering the water treatment plant, debris transported through the flowlines from the lakes is filtered out through coarse screens.
-
The water then travels into a "Rapid Mix" and Aluminum Sulfate (alum) and cationic polymer are address thus beginning the water treatment process. This is called coagulation. The particles in the water cling to the Alum and polymers, forming larger particles called floc. This is called flocculation.
-
After mixing, the water and the floc flow into s sedimentation basin. Here the floc settles to the bottom and is pumped from the water to sludge thickening basins for disposal.
-
From the sedimentation basin, the water flow through filter beds made of several layer of activated carbon (coal) and sand to remove any remaining particles left in the water.
-
Fluoride is then added to reduce tooth decay, and a small amount of chlorine is added to kill any remaining germs and to keep the water safe as it travels to the public.
-
The water then flows to a closed tank or reservoir called a clearwell. The water winds its way through a maze of baffles to give the chlorine time to mix throughout the water for complete disinfection.
-
Finally, the water flows into the distribution system. Tulsa enjoys an abundant water supply and plants are capable of treating 220 million gallons of water per day.
The Drinking Water Treatment Process is of interest to people of all ages. As part of our Water Education program over the past several years, we have been providing tours of the Mohawk Water Treatment Plant. The following graphic is useful when simplifying the steps that are taken in the treatment process.
Note the source lakes depicted at the top of the cartoon, and our two Drinking Water Treatment Plants, A.B. Jewell and Mohawk.
Steps 1-5 describe the basic events of the treatment process.
Step 6 indicates that the water is pumped from the treatment plant to Tulsa customers as well as many rural water districts and neighboring communities.
The cartoon graphic also depicts some of the water storage towers located around Tulsa. The water levels in these storage towers are constantly monitored at the treatment plants. Operators watch these levels to be sure that the towers are filling with new water at about the same rate as they are being emptied out by consumers.
Recent Taste and Odor Issues
In the last eight years, the City of Tulsa has spent millions of dollars to get rid of taste and odor problems in our drinking water. The water comes from Lakes Eucha and Spavinaw, two of the city’s three primary sources for water.
What causes these taste and odor problems? The high growth rates of certain algae in these lakes has caused these taste and odor problems. When there is too much phosphorus in a lake, too much algae grows. These plants release chemicals as a natural part of their life cycle. It is those chemicals that affect the taste and odor of our water.
So where does this phosphorus come from? Runoff from land around the lakes brings in this extra phosphorus. Phosphorus is a natural chemical nutrient primarily found in fertilizers and in animal waste. As water travels downhill in the watershed, it picks up and carries nutrients like phosphorus from the surface, the soil, and from where it has seeped underground. Studies conclude that extra phosphorus has accumulated in these watersheds.
What has caused this accumulation? These same studies show that the excess phosphorus has built up primarily from years of using poultry waste as a fertilizer in farming operations. Over the years, companies have built more and more poultry operations in Oklahoma and Arkansas, in the watershed for Lakes Eucha and Spavinaw. This means that more and more birds create more and more poultry waste every year. Until recently, most of that waste was applied within the area as a fertilizer.
In recent years, the poultry industry has been required to reduce the amount of poultry waste used as fertilizer within this area. But farmers are still applying the waste. Any additional waste adds to the existing problem. No one knows how many years it will take for run off to flush the existing phosphorus through the watershed. It may be many years before phosphorus levels in the lake return to normal so that extra treatment to eliminate taste and odor problems is not required in Tulsa’s water.