Did You
KNOW?

  • The cost of one bottle of water from a vending machine is equivalent to the cost of drinking 8 glasses of tap water every day for a year.
  • A gallon of water weighs 8.34 pounds.
  • The Water Authority maintains almost 1500 miles of drinking water pipes. If you put them end-to-end, they would stretch from Roanoke to Colorado Springs, CO.
  • At one drip per second, a faucet can leak 3,000 gallons of water per year.
  • Water is the only substance naturally found on earth as a solid, liquid and gas.
  • Over 713 gallons of water go into the production of one cotton T-shirt.
  • The Authority’s Water Pollution Control Plant is regarded as one of the best bird-watching areas in the mid-Atlantic region.
  • The Water Authority maintains over 6,000 fire hydrants in our service area. Fire hydrants are connected to the public drinking water distribution lines, so water from a fire hydrant is drinking water.
  • There are over 23,000 manholes in our service area.
  • Carvins Cove Natural Reserve is the second largest municipal park in the United States.
  • The Authority’s Water Pollution Control Plant covers over 100 acres of land.
  • More people in the world have a mobile phone than have a toilet.
  • The Water Authority treats 19-million gallons of drinking water a day although we have the capacity to treat 56-million gallons per day.
  • The Authority’s Water Pollution Control Plant treats almost 37-million gallons of wastewater a day from all across the Roanoke Valley.
  • There are 51 drinking water storage tanks in our service area. They each hold between 500,000 – 2-million gallons of water.
  • Most of the treated drinking water used in a home is for toilet flushing.

water drops

Wastewater Treatment

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treatment process
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biosolids lagoons wide
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PFE at WPCP
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The Roanoke Regional Water Pollution Control Plant provides tertiary treatment for an average of 37-million gallons of sanitary sewer a day from all jurisdictions in the Roanoke Valley. A drop of water entering the Regional Water Pollution Control Plant takes approximately 19 hours to move through all levels of the liquid treatment process.

Along the way, more than 3,000 lab tests are conducted every month to verify that the liquid treatment process is meeting or exceeding water quality standards. The Regional Water Pollution Control Plant has some of the most stringent requirements for treatment of any plant in Virginia.

Recent Facility Improvements

 

Our Treatment Process

 

Liquids Treatment


Headworks at WPC

 

 

  

Headworks

 

Before the wastewater begins the series of treatment processes, the flow travels up the new Archimedes screw pumps to begin preliminary treatment. Bar screens remove large objects that are disposed of in the landfill. This new equipment will convey and treat significantly higher wet weather flows.


 

primaries

 

 

 

 

 Primaries

 

Metal bars, known as flights, skim across the surface of the water in the settling tanks to remove the floating scum before turning downward to scrape away the material that has settled at the bottom of the tank.

 

 

Aeration 

 

 

 

Aeration

 

After leaving the primary clarifiers, wastewater travels to one of 16 aeration tanks where air is blown into the flow to raise the dissolved oxygen levels, sustaining the microorganisms that consume the organic material (carbonaceous Biochemical Oxygen Demand - BOD) in the wastewater. This process takes 4-6 hours; all the while microorganisms are feeding on and removing the organic matter carried in the flow.

The WPC Plant has a modern design which utilizes a common aeration basin to complete carbonaceous BOD removal and nitrification in one unit. Modification to this “single stage process” allowed a substantial capacity increase through better use of existing infrastructure.

 

 coagulation and settling

 

 

 

 

Coagulation

 

By this step of the treatment process, only very small particles remain. Chemicals, such as iron salts (ferric chloride) and polymers, are added to make the tiny particles bind together in masses called floc. The floc is large enough to settle to the bottom of the coagulation tanks or be caught in the filtration process.

 

Filtration

The flow is passed through one of ten deep bed monomedia filters as the final purification process before the flow goes to the chlorine chamber for disinfection.

 

disinfection
 

 

 

  

Disinfection

Pathogens are removed throughout the treatment process, but the final step of chlorination guarantees the quality and safety of the water discharged into the Roanoke River. The water must remain in contact with the chlorine for 20 minutes to ensure that all the pathogens are killed. The water is then treated with sulfur dioxide to remove all chlorine before the flow enters the river. 

   

receiving river

 

 

 

 

 Receiving River

 

After more than 19-hours of treatment, the water is fully treated and ready to go to the receiving river where it will be used many times again for drinking water, recreation and aquatic habitat.  The Roanoke Regional Water Pollution Control Plant consistently meets some of the strictest permitting standards in the state to ensure that only healthy, clean water is discharged into the river.

 

 

Solids Treatment


Digestion

 

 

 

 

Digestion

Sludge from primary and secondary clarifiers is heated and mixed to promote the anaerobic consumption of organic material by bacteria contained within the tanks. First, acid forming bacteria use the organic material energy supply to produce organic acids and carbon dioxide. A second group of bacteria, the gas formers, breaks down the organic acids to make methane and carbon dioxide gas. The waste methane is then cleaned and converted into electricity and thermal heat to offset energy costs at the plant.

 

 

biosolids lagoons

 

 

  

 

Biosolid Lagoons

After the digestion is finished, the sludge is pumped to the lagoons to complete treatment. Both anaerobic and aerobic bacteria consume any remaining organic matter and solids settle to the bottom of the ponds.

biosolids

 

  

Land Application

 

After about nine months, the fully processed material is applied to non-food crop farms as fertilizer at no cost to the farmers. The application process and quality of the biosolids is held to strict standards set forth and enforced by the EPA.

 

 Cogen Units

 

 

Converting Methane to
Electricity

In 2012, the Western Virginia Water Authority installed two grant-funded 500-kW generators designed to run on waste methane gas from the digestion process. The combined heat and power (CHP) system supplies thermal energy to heat the existing digesters and electrical power that is used by the plant to reduce the plant’s electrical utility power usage. Excess heat not used by the digesters supplies thermal energy to absorption chillers to heat and cool the buildings located on the plant site, further reducing the plant’s electric usage.

The CHP generation system offsets approximately 7,577 MWH of purchased electrical power annually. Depending upon facility flows and energy demand, the generation capacity represents between 30% to 50% of the plant’s energy usage. An estimated 4600 metric tons of greenhouse gas emissions is reduced annually.