Water Management
Water Supply and Treatment Division
Mission
1) To provide an adequate supply of safe drinking water for all citizens, and;
2) To maintain compliance with all local, state and federal regulatory requirements.
The Water Supply and Treatment Division is responsible for operating the two water treatment facilities and the Lake Michie and Little River Lake pumping stations. Durham's raw water supply is provided by the Lake Michie reservoir (pictured right), which was completed in 1926, and Little River reservoir, which was completed in 1987. These two lakes have a combined safe yield of 37 million gallons per day (MGD). The pump stations operate 24 hours a day, using the most efficient combination of gravity flow and electric and hydro-powered pumps, to deliver lake water to either of the two water treatment plants. The Williams Water Treatment Plant (WTP), with a capacity of 22 MGD, and the Brown WTP, with a capacity of 39 MGD, treat the raw water to meet stringent State and Federal water quality criteria before pumping into the distribution system. The annual daily average water production of the combined facilities was approximately 27.65 MGD in 2005 with a peak daily production of 38.3 MGD in July of 2005.
Children and adults can read, watch, and listen to the Story of Drinking Water to learn more about water and water treatment.
*"Story of Drinking Water" site can be made available on alternative media suited to the needs of disabled individuals upon request. To make a request, please email James Lim.
Water Treatment Process
The City treats and purifies the raw water it receives from Lake Michie and the Little River Reservoirs before sending it out into the water supply system. Drinking water treatment requires a delicate balance of a number of factors in order to assure that you, the consumer, receive water meeting all requirements for safety at your tap. The following is a description of the water treatment process.
Terminal Reservoirs and Treatment Plants
Raw water from Durham’s two reservoirs arrives at terminal reservoirs located next to the City’s two water treatment plants - the Brown and Williams plants which have a 30 million gallon per day (MGD) and 22 MGD treatment capacity respectively. The Brown Plant terminal reservoir holds approximately 90 million gallons and the Williams Plant Terminal reservoir holds approximately 45 million gallons representing a two to three day supply of water and providing a constant supply of raw water for the treatment plants should any interruption in delivery occur from the reservoirs due to water line servicing or breaks.
Coagulation, Flocculation and Sedimentation
Raw water enters the treatment plants from the terminal reservoirs and first goes through the clarifiers where sediment and other particulate matter are removed by processes known as coagulation, flocculation and sedimentation. Coagulation occurs with the help of chemicals known as coagulants that use their positive charges to attract negatively charged particles like sediment and organic matter in raw water. Flocculation then occurs as these particles clump together and form flocs, or clumps of sediment and particulate matter. These flocs are then allowed to settle to the bottom of the clarifier by sedimentation where rake-like structures slowly scoop the solid matter out. Clear, sediment-free water leaves the clarifier from the top and flows onto the next step in the treatment process. Currently, both treatment plants use a chemical called aluminum sulfate or "alum" as a coagulant.
Filtration
After water has gone through a flocculation and sedimentation process, which removes the bulk of sediment and particulate matter, it flows through filters composed of layers of crushed anthracite coal, sand and gravel. The filtration process removes additional particles not removed by the flocculation and sedimentation process.
Disinfection and Chemical Addition
Treatment chemicals are added to the water throughout the treatment process. They include chemicals for disinfection (chloramines), corrosion inhibition (orthophosphate), pH balance (sodium hydroxide) and dental health (fluoride). The concentrations of each of the majority of these chemicals must meet EPA standards. Below is a brief description of each additive. For a description about Durham’s water quality in general visit our Water Quality webpage.
Chloramine (CLNH3)
In January of 2002, the City of Durham began using chloramination as the method of disinfection for drinking water. Chloramination uses both ammonia and chlorine to disinfect water. The chlorine and ammonia react chemically to produce combined chlorine or chloramine, which is an effective method for killing many types of bacteria and other germs. Chloramination reduces the formation of disinfection by-products in the water distribution system. The City maintains a running annual average concentration of 2.8 mg/L or parts per million (ppm) of chloramines in water leaving the City’s treatment plants. For information on the City’s use of chloramines as a disinfectant, click here. Free Adobe Acrobat Reader plugin required.
Zinc Orthophosphate (ZnPO4)
The City of Durham has used zinc orthophosphate to inhibit corrosion in service lines and household plumbing since the 1970s. Phosphates create a protective coating on metal surfaces and reduce water’s chemical activity, which decreases the processes that lead to corrosion. The City currently adds 0.8 mg/L (ppm) of zinc orthophosphate to water leaving the City’s treatment plants
Sodium Hydroxide (NaOH)
Balancing the acidity of our drinking water is a very important part of the treatment process. pH is a measure of a liquid’s acidity where acids are defined as having a pH below 7 and bases as having a pH above 7 to 14. Stronger acids have lower pH’s and stronger bases have higher pH’s. In 2005, the pH of Durham’s water ranged from 7.1 to 8.2 (7 being neutral).
Fluoride (H2SiF6)
Fluoride has been added to Durham’s drinking water since 1960’s in order to prevent tooth decay in the form of hydrofluorosilic acid. According to the American Dental Association (ADA), "fluoridation is a safe and effective means of preventing tooth decay. It has been cited by the Centers for Disease Control and Prevention as one of 10 great public health achievements of the 20th century. Studies show that fluoridation can prevent between 15–40 percent of decay." The ADA cites over 60 years of studies supporting this conclusion. The City maintains a fluoride concentration that ranges from 0.65 to 0.99 mg/L (ppm) in our drinking water.
Visit the American Dental Association for more information on Fluoride in drinking water..
Storage and Distribution
Now clean and treated, drinking water is stored in covered tanks called clear wells. The City stores several millions of gallons of treated water in each clear well to have ready for distribution. Water levels in towers located throughout the City are monitored in order to determine how much water should be sent out into the system. Towers and elevated tanks provide pressure for the distribution system so that each household and business has sufficient flow.
Water Supply and Treatment personnel also respond to complaints about water quality and oversee the collection and analysis of distribution system samples to monitor overall system water quality.
If you are experiencing a problem with a pink film or residue on your bathroom and kitchen fixtures, click here for more information.
For more information about drinking water quality, read the most recent "Annual Water Quality Report" or call (919) 560-4362.
View the Annual Water Quality Report - 2006
View the Annual Water Quality Report - 2005
View the Annual Water Quality Report - 2004
View the Annual Water Quality Report - 2003
View the Annual Water Quality Report - 2002
View the Annual Water Quality Report - 2001
View the Annual Water Quality Report - 2000
(Adobe Acrobat Reader is required to view these pdf documents)
Mission
1) To provide an adequate supply of safe drinking water for all citizens, and;
 |
The Water Supply and Treatment Division is responsible for operating the two water treatment facilities and the Lake Michie and Little River Lake pumping stations. Durham's raw water supply is provided by the Lake Michie reservoir (pictured right), which was completed in 1926, and Little River reservoir, which was completed in 1987. These two lakes have a combined safe yield of 37 million gallons per day (MGD). The pump stations operate 24 hours a day, using the most efficient combination of gravity flow and electric and hydro-powered pumps, to deliver lake water to either of the two water treatment plants. The Williams Water Treatment Plant (WTP), with a capacity of 22 MGD, and the Brown WTP, with a capacity of 39 MGD, treat the raw water to meet stringent State and Federal water quality criteria before pumping into the distribution system. The annual daily average water production of the combined facilities was approximately 27.65 MGD in 2005 with a peak daily production of 38.3 MGD in July of 2005.
Children and adults can read, watch, and listen to the Story of Drinking Water to learn more about water and water treatment.
*"Story of Drinking Water" site can be made available on alternative media suited to the needs of disabled individuals upon request. To make a request, please email James Lim.
Water Treatment Process
The City treats and purifies the raw water it receives from Lake Michie and the Little River Reservoirs before sending it out into the water supply system. Drinking water treatment requires a delicate balance of a number of factors in order to assure that you, the consumer, receive water meeting all requirements for safety at your tap. The following is a description of the water treatment process.
 |
Raw water from Durham’s two reservoirs arrives at terminal reservoirs located next to the City’s two water treatment plants - the Brown and Williams plants which have a 30 million gallon per day (MGD) and 22 MGD treatment capacity respectively. The Brown Plant terminal reservoir holds approximately 90 million gallons and the Williams Plant Terminal reservoir holds approximately 45 million gallons representing a two to three day supply of water and providing a constant supply of raw water for the treatment plants should any interruption in delivery occur from the reservoirs due to water line servicing or breaks.
Coagulation, Flocculation and Sedimentation
 |
Raw water enters the treatment plants from the terminal reservoirs and first goes through the clarifiers where sediment and other particulate matter are removed by processes known as coagulation, flocculation and sedimentation. Coagulation occurs with the help of chemicals known as coagulants that use their positive charges to attract negatively charged particles like sediment and organic matter in raw water. Flocculation then occurs as these particles clump together and form flocs, or clumps of sediment and particulate matter. These flocs are then allowed to settle to the bottom of the clarifier by sedimentation where rake-like structures slowly scoop the solid matter out. Clear, sediment-free water leaves the clarifier from the top and flows onto the next step in the treatment process. Currently, both treatment plants use a chemical called aluminum sulfate or "alum" as a coagulant.
 |
After water has gone through a flocculation and sedimentation process, which removes the bulk of sediment and particulate matter, it flows through filters composed of layers of crushed anthracite coal, sand and gravel. The filtration process removes additional particles not removed by the flocculation and sedimentation process.
Disinfection and Chemical Addition
Treatment chemicals are added to the water throughout the treatment process. They include chemicals for disinfection (chloramines), corrosion inhibition (orthophosphate), pH balance (sodium hydroxide) and dental health (fluoride). The concentrations of each of the majority of these chemicals must meet EPA standards. Below is a brief description of each additive. For a description about Durham’s water quality in general visit our Water Quality webpage.
Chloramine (CLNH3)
In January of 2002, the City of Durham began using chloramination as the method of disinfection for drinking water. Chloramination uses both ammonia and chlorine to disinfect water. The chlorine and ammonia react chemically to produce combined chlorine or chloramine, which is an effective method for killing many types of bacteria and other germs. Chloramination reduces the formation of disinfection by-products in the water distribution system. The City maintains a running annual average concentration of 2.8 mg/L or parts per million (ppm) of chloramines in water leaving the City’s treatment plants. For information on the City’s use of chloramines as a disinfectant, click here. Free Adobe Acrobat Reader plugin required.
Zinc Orthophosphate (ZnPO4)
The City of Durham has used zinc orthophosphate to inhibit corrosion in service lines and household plumbing since the 1970s. Phosphates create a protective coating on metal surfaces and reduce water’s chemical activity, which decreases the processes that lead to corrosion. The City currently adds 0.8 mg/L (ppm) of zinc orthophosphate to water leaving the City’s treatment plants
Sodium Hydroxide (NaOH)
Balancing the acidity of our drinking water is a very important part of the treatment process. pH is a measure of a liquid’s acidity where acids are defined as having a pH below 7 and bases as having a pH above 7 to 14. Stronger acids have lower pH’s and stronger bases have higher pH’s. In 2005, the pH of Durham’s water ranged from 7.1 to 8.2 (7 being neutral).
Fluoride (H2SiF6)
Fluoride has been added to Durham’s drinking water since 1960’s in order to prevent tooth decay in the form of hydrofluorosilic acid. According to the American Dental Association (ADA), "fluoridation is a safe and effective means of preventing tooth decay. It has been cited by the Centers for Disease Control and Prevention as one of 10 great public health achievements of the 20th century. Studies show that fluoridation can prevent between 15–40 percent of decay." The ADA cites over 60 years of studies supporting this conclusion. The City maintains a fluoride concentration that ranges from 0.65 to 0.99 mg/L (ppm) in our drinking water.
Visit the American Dental Association for more information on Fluoride in drinking water..
Storage and Distribution
 |
Water Supply and Treatment personnel also respond to complaints about water quality and oversee the collection and analysis of distribution system samples to monitor overall system water quality.
If you are experiencing a problem with a pink film or residue on your bathroom and kitchen fixtures, click here for more information.
For more information about drinking water quality, read the most recent "Annual Water Quality Report" or call (919) 560-4362.
View the Annual Water Quality Report - 2006
View the Annual Water Quality Report - 2005
View the Annual Water Quality Report - 2004
View the Annual Water Quality Report - 2003
View the Annual Water Quality Report - 2002
View the Annual Water Quality Report - 2001
View the Annual Water Quality Report - 2000
(Adobe Acrobat Reader is required to view these pdf documents)