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Wastewater and Biosolids Treatment and Recycling Annual Report for 2010-11








In February, 2011 we began a $4.85 million project to replace our sewer along Bolin Creek between Martin Luther King Jr. Boulevard and Estes Drive. This project is part of our work to protect the public health and the environment by preventing overflows from our sewers. The existing sewer in this area is deteriorating and our studies showed that wastewater flows are approaching the pipe’s capacity.


From July, 2010 through June, 2011, we collected, treated and recycled 2.7 billion gallons of wastewater, or an average of about 7.2 million gallons per day. We surpassed all of the water quality standards for our Mason Farm Wastewater Treatment Plant (WWTP) including the limits on bacteria, phosphorus, nitrogen and solids.

The University used about 170 million gallons of our highly treated wastewater in a “reclaimed water” system that meets non-drinking water needs such as chilled water for cooling systems, irrigation and toilet flushing at certain facilities.

Most of our treated wastewater is returned to Morgan Creek, a tributary of Jordan Lake. Jordan Lake is a water source for several communities in the Triangle and will be a future water resource for our community.

We treated and recycled 1,279 tons of biosolids, or an average of 3.5 tons per day. We turn wastewater solids into a reusable resource called biosolids through a biological process (“digestion”), in which bacteria and other microorganisms break down the solids into simpler compounds; and by heating the solids to about 140 degrees to kill pathogens.

Our biosolids continue to meet Federal standards for “Exceptional Quality.” Laboratory testing shows that our biosolids have very low levels of pathogens and metals, as reported below.

There were seven overflows from our sanitary sewers in 2010-11. The overflows totaled an estimated 4,475 gallons or a small fraction of one percent of the total wastewater volume we treated.


We maintain 322 miles of sewers, which receive wastewater from homes, businesses, schools, etc.; and we have 21 facilities to pump wastewater uphill where necessary, but most of our sewers work with the simple force of gravity.

Wastewater overflows from our sewer system

Wastewater may overflow from a sewer which is damaged; when the flow in a sewer is blocked by fat, oil, grease, trash, debris or roots; or if the flow in a sewer exceeds the pipe’s capacity. Usually, overflows occur at a sewer manhole that is upstream of where a sewer is blocked. To help prevent overflows, please:

  • dispose of residential fat, oil and grease (FOG) and trash with refuse taken to the landfill; or recycle used cooking oil at Orange County’s Household Hazardous Waste Program on Eubanks Road near the landfill. Restaurants and related businesses are required to have traps from which waste grease is regularly removed and recycled by commercial haulers.
  • do not plant trees or shrubs (or install fences or other structures) in an OWASA sewer easement without OWASA’s approval. If tree and shrub roots grow inside a sewer, they can form a dense mat that will block the sewer.

Your dollars at work: What we do to prevent wastewater overflows and protect the environment

Inspecting the inside of our sewers with a special videocamera to find cracks and leaks (where stormwater and groundwater may enter and exceed the capacity of our pipes) and accumulations of grease, roots, debris, etc. to identify where repairs, cleaning, etc. are needed. In 2010-11, we inspected eight miles of sewers.

  • Testing for cracks and leaks by putting non-toxic smoke in sewer lines.
  • Routinely cleaning our sewers with high pressure water and special cutters to remove roots, grease and debris. In 2010-11, we cleaned about one-third of our sewers. 
  • Fixing leaks and cracks in our sewers to keep out stormwater, groundwater and the roots of trees and shrubs.
  • Mowing and otherwise clearing our sewer easements in off-street areas to help keep tree and shrub roots from growing into and blocking sewers, and to keep safe, open access for maintenance work and responding to overflows. In 2010-11, we mowed about two-thirds of our easements.
  • Resealing the inside of sewers to keep out groundwater and stormwater, and replacing sewers where needed to maintain structural integrity and ensure adequate capacity to handle future wastewater flows. In the next five years, we will spend about $15.6 million for sewer projects including completion of the sewer replacement now underway along Bolin Creek.

LEFT: A still photo from a video inspection inside an OWASA sewer. The arrow indicates the growth of roots that will block the flow of wastewater. In 2010-11, roots caused or contributed to a majority of the overflows from our sewer system. Before planting in an OWASA easement, please contact us at 968-4421 or to discuss your plans and get information on the kinds of shallow-rooted trees and shrubs that may be allowed in the outer part of an easement. 



Our treatment process

The Mason Farm Wastewater Treatment Plant uses a modern and complex system of physical, chemical and biological processes to make the dirty water clean. The plant is run by highly-trained and State-certified operators who use a state-of-the-art computer control system. We surpassed all of the water quality standards for our Mason Farm Wastewater Treatment Plant (WWTP) including the limits on bacteria, phosphorus, nitrogen and solids.


Some of our highly treated wastewater is recycled in our reclaimed water system (please see additional information on page 4) but most is returned to the natural environment at Morgan Creek in southeast Chapel Hill. Morgan Creek flows to Jordan Lake, which is a water supply for the Towns of Cary, Apex and Morrisville and for Chatham County.

In the future, the City of Durham, OWASA, and other water utilities may also draw water from Jordan Lake.

Odor control

We are working to eliminate off-site odor from our Mason Farm Wastewater Treatment Plant through improvements to capture and treat foul air.

Since 2000, we have spent $6.6 million for odor control, primarily to enclose structures that previously released odor into the open air and to treat foul air before release. Operating costs for odor control are about $100,000 annually.

By the end of 2014, we will complete additional improvements at a cost of about $4 million.


The solids that are separated from wastewater are treated in a 30-day biological process called digestion, and heated to about 140 degrees to kill pathogens. When treated, solids are called biosolids.

Our biosolids surpass the U.S. Environmental Protection Agency’s standards for Exceptional Quality, as shown below.


* One part per million is like a penny in $10,000.

Most of our biosolids are recycled on farmlands approved by the State. Biosolids include nitrogen and phosphorus (the key ingredients in fertilizers), so they are a resource for local farmers.

We dewater some of our biosolids to the consistency of moist soil. OWASA’s dewatered biosolids are mixed with other organic material at a private composting facility in Chatham County to produce a soil additive used in landscaping.


Reclaimed water (RCW) is highly treated wastewater which can be used for various non-drinking purposes. Like other wastewater, RCW undergoes biological treatment, filtration, and disinfection with ultraviolet light. We also add chlorine for disinfection while RCW is stored and carried through the RCW pipe system.

Our RCW system went into operation in April, 2009, initially to serve certain University facilities (chiller plants, which cool campus buildings) which had used drinking water for non-drinking purposes. The University and State and Federal grants funded construction of the RCW system. The University pays monthly fees to cover the costs of RCW service to the University. In June, 2010, St. Thomas More School also began using RCW on a cost-of-service basis to irrigate athletic fields.

From July, 2010 through June, 2011, the University used an average of 461,000 gallons of reclaimed water per day. In 2011-12, reclaimed water will meet more than 10% of the community’s overall water needs.


In the summer of 2010, following a consultant’s study of how to optimize the operation of our Mason Farm Wastewater Treatment Plant, we made refinements that reduced our chemical and energy costs by about $300,000 annually. Essentially, the changes involve more effective use of biological processes for removing pollutants from wastewater.


Pharmaceutical compounds in the water environment are an area of scientific research regarding how they may affect people and wildlife. The U.S. Environmental Protection Agency’s guidelines for medication disposal are: 

  • Do not flush prescription drugs down the toilet or drain unless the label or accompanying information specifically instructs you to do so. For information on drugs that should be flushed, please click here.
  • Call your city or county government’s household trash and recycling service and ask if a drug take-back program is available. [The Orange County Department of Solid Waste Management can be reached at 968-2788.]
  • If a drug take-back or collection program is not available:
  • Take your prescription drugs out of their original containers.
  • Mix drugs with an undesirable substance, such as cat litter or used coffee grounds.
  • Put the mixture into a disposable container with a lid, such as an empty margarine tub, or into a sealable bag.
  • Conceal or remove any personal information, including the Rx number, on the empty containers by covering it with black permanent marker or duct tape, or by scratching it off.
  • Place the sealed container with the mixture, and the empty drug containers, in the trash.


Whenever you have comments or questions about wastewater, biosolids or reclaimed water services, or if you would like to arrange a tour of our Mason Farm Wastewater Treatment Plant and/or biosolids facilities, please contact us at 968-4421 or