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. 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 decade, 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.

Chart — Mohawk Taste and Odor Cost 98-05

General Water Quality

For information about what these terms mean, read below.

Water Treatment Terms

Many measurements contribute to a determination of water quality. Such measurements may affect the taste of water, but not necessarily whether or not it is safe to drink. These measurements are frequently reported when considering water quality.

Alkalinity
Alkalinity is a measure of bicarbonate, carbonate, or hydroxide ions.  A low level of alkalinity is desirable because it acts as a buffer and prevents large variations in pH. Alkalinity is not detrimental to humans. Moderately alkaline water (less than 350 mg/l); in combination with hardness, forms a layer of calcium or magnesium carbonate that tends to inhibit corrosion of metal piping. This practice is in use to reduce pipe corrosion and to increase the useful life of the water distribution system. High alkalinity (above 500 mg/l) is usually associated with high pH values, hardness and high dissolved solids and has adverse effects on plumbing systems, especially on hot water systems (water heaters, boilers, heat exchangers, etc.) where excessive scale reduces the transfer of heat to the water, thereby resulting in greater power consumption and increased costs.

Hardness
The term hardness was originally applied to waters that were hard to wash in, referring to the soap wasting properties of hard water. Hardness prevents soap from lathering by causing the development of an insoluble curdy precipitate in the water; hardness typically causes the buildup of hardness scale (such as seen in cooking pans). Dissolved calcium and magnesium salts are primarily responsible for most scaling in pipes and water heaters and cause numerous problems in laundry, kitchen, and bath. Hardness is usually expressed in grains per gallon (or ppm) as calcium carbonate equivalent.

Fluoride
Fluoride in drinking water decreases the occurrence of tooth decay when the water is consumed during the period of enamel calcification. The USEPA has an upper allowable limit of 1.2 ppm for fluoride in drinking water.

Conductivity
Conductivity or specific conductance is a measure of the ability of a fluid to carry a charge which is directly related to the concentration of dissolved substances. As the total dissolved substances in the water increases, the conductivity of the water also increases.

Chlorine Residual
Chlorine allowed to remain in water after a specified period of contact time and to provide disinfection protection throughout the distribution system. The amount of residual chlorine is the difference between the total chlorine added and that consumed by the oxidizable matter.

Turbidity
Turbidity is the cloudy appearance of water caused by the presence of tiny particles. High levels of turbidity may interfere with proper water treatment and monitoring.

pH
pH is a numerical measure of the acidity or alkalinity of water. The pH scale ranges from 1 (acidic) to 14 (alkaline). A pH of 7 is neutral.