Wastewater Collection
and Treatment

2005-06 Annual Report

Above: One of the monitoring and control panels for the new filters and ultraviolet light disinfection system at our Mason Farm Wastewater Treatment Plant. The monitoring system continuously checks operating conditions such as water flow levels and makes automatic adjustments as needed

Wastewater Collection

The public wastewater collection or sewer system includes a network of about 300 miles of sewer mains, 24 pump stations and more than 9,800 manholes. Most sewers operate simply with the force of gravity, but in some places it is necessary to pump wastewater uphill for a short distance.

Wastewater Spills in 2005-06

From July 1, 2005 through June 30, 2006, there were two known spills from the OWASA wastewater system and they totaled 145 gallons.  During the 2005-06 service year, we received, transported, treated and recycled about 2.72 billion gallons of wastewater.                                                                   

Typical cause(s) of wastewater spills

Grease from residences and businesses enters sewers. The grease hardens, accumulates and blocks the flow of wastewater; then wastewater spills out of a manhole upstream of the blockage.

Tree and shrub roots grow into sewer lines, creating blockages.

Debris or trash in sewers blocks the flow of wastewater.

Settling of soil beneath a sewer causes the pipe to break.

Stormwater enters sewers through cracks and breaks, increasing volume of flows beyond pipe capacity.

Pumps stop working due to loss of power, electrical surges, mechanical failure, etc.

What we do to prevent spills

Inspect, repair, renovate or replace sewers and pump stations as needed to eliminate leaks and increase system capacity.

Clear sewer pipes with cutting and flushing equipment to remove roots, grease accumulations, etc. before they block the wastewater flow and cause a spill from a manhole.

Mow and otherwise clear our off-street sewer easements to keep roots from growing into sewers and to maintain safe, timely access for emergency repairs and other work. Most of our easements are 30 feet wide (15 feet on each side of the sewer).

Inform OWASA customers about proper grease disposal; work with restaurants and other food businesses regarding the need to have and to properly maintain grease traps, and to recycle used grease.

Operate a continuous monitoring and alarm system at pump stations; maintain and repair pumps; use generators for backup power; replace pump stations with gravity sewers when practical; monitor and inspect pump stations to identify improvement needs.

Ask customers to contact OWASA if they see debris or trash being put in the sewer system.

Corrective actions

Follow-up actions depend on the cause and severity of the spill and may include:

cleanup and disinfection;

inspection and clearing of sewer mains;

increased inspections or other maintenance;

evaluation of alternatives for preventing recurrence through operational or facility improvements;

repair, renovation or replacement of pipes; and

in some cases, replacement of sewers or pump equipment with larger capacity facilities

We also report the spill to the NC Division of Water Quality and notify the community about the overflow through an electronic news release to local media, local governments, neighborhood groups for which we have e-mail addresses, etc.

No substantial or lasting effects, such as fish kills, are known
to have resulted from these wastewater spills.

In 2005-06, our crews mowed and cleared 140 miles of off-street sewer easements (see photo below) to maintain safe access for repairs and other work, and to prevent tree and shrub roots from growing into sewer pipes and blocking them.

In 2005-06, OWASA crews cleaned about 159 miles of sewers and made 21 repairs to our 296-mile network of sewers. This work helps reduce wastewater overflows by removing roots, grease, etc. before they block pipes.

Do you have plantings or a structure in an OWASA easement?

If an OWASA sewer crosses your property and any  trees, shrubs, a shed, etc. appear to be in our easement, please contact us at 968-4421 if you have not already done so. We’ll be glad to meet with you, show you the easement’s location and to discuss items that would affect our access through the easement, types of shallow-rooted plantings that may be suitable in the outer part of the easement, etc.

Down the Drain?

If you are not sure whether to dispose of waste through the public sewer system, please call us at 968-4421.

We also invite you visit our Website page at www.owasa.org/pages/Q&AonDisposal.htm for more detailed information.

Here are some basic rules of thumb about safe use of the public sewer system and your plumbing drains.

•  Our community's wastewater system is designed to collect and treat normal liquid wastes such as bodily waste and water from routine washing, bathing, cleaning and food preparation.

•  Fat, oil and grease (FOG) should not go down the drain. Please see the related section of this annual report for more information about FOG disposal.

•  Liquids and other substances that are corrosive, explosive or flammable may damage your plumbing drains, the sewer system and/or the wastewater treatment facility.

For information about Orange County 's Landfill and the Household Hazardous Waste program, please contact the County's Solid Waste staff at 968-2788.

Wastewater Treatment

Our Mason Farm Wastewater Treatment Plant uses biological, chemical and physical processes to clean wastewater and return highly treated water to the natural environment at Morgan Creek in southeast Chapel Hill . The solid particles separated from wastewater in the treatment process are converted into “biosolids” that are recycled on farmland to help grow crops for non-human consumption.

Definitions

Ammonia-- A compound of nitrogen and hydrogen that exerts a demand for oxygen in water, acts as a nutrient for plant life in surface waters and can be toxic to fish and other aquatic life.

Carbonaceous biochemical oxygen demand (CBOD)-- A measure of the carbon-containing substances remaining in treated water that may exert a demand for oxygen when released into a stream. The lower the CBOD, the less likely there is to be an appreciable oxygen demand placed on the receiving waters. Adequate dissolved oxygen is important for fish and other aquatic life.

Chlorine--- The disinfecting element in liquid bleach (sodium hypochlorite), which we use to kill microorganisms in treated wastewater.

Dissolved oxygen-- Oxygen which is dissolved in water, and can be breathed by and is necessary for the health of fish and other aquatic animals.

Fecal coliform bacteria-- Bacteria that are naturally present in the intestines of people, dogs, cats and other animals.

Milligrams per liter-- A measure of concentration. One milligram per liter corresponds to one part per million or one penny in $10,000.

Micrograms per liter-- A measure of concentration. One microgram per liter corresponds to one part per billion or one penny in $10 million.

Phosphorus-- An element that acts as a nutrient for plant life such as algae in creeks and lakes.

Total suspended solids-- A measure of small particles remaining in treated wastewater. Excludes dissolved substances.

Wastewater-- Water after it has been used for household, business and other purposes. Wastewater flows from private plumbing systems to public sanitary sewers and then to a treatment plant. Wastewater differs from stormwater, which flows to creeks and streams through a separate network of ditches, catch basins and pipes.

Treated wastewater quality

Noncompliance event at the Mason Farm Wastewater Treatment Plant

From January through March, 2006 the phosphorus level in our treated wastewater averaged 0.68 milligrams per liter and exceeded the limit of 0.60. This exceedance resulted from temporary conditions related to dewatering of biosolids.

No fish kills or other significant downstream impacts resulted.

You can help avoid the cost and inconvenience of clogged plumbing drains and help prevent wastewater overflows by not letting “FOG” into your plumbing drains. “FOG” refers to fat, oil and grease.

Inside a sewer, fat, oil and grease change to a plaster-like consistency and can block the pipes, causing an overflow of wastewater out of a manhole and into the natural environment.

At home, you can dispose of normal cooking oil and grease by putting it in a container as part of your solid waste rather than down your sink and plumbing drain.  Wiping and scraping pots, pans and other utensils before washing them are important steps in proper FOG disposal.

If your business generates waste fat, oil and grease, a grease trap that works effectively in accord with OWASA standards is required. A company that recycles fat, oil and grease should regularly clean out the grease trap.

For more information, please call OWASA’s Collection and Distribution Systems staff at 537-4226 or send e-mail to webmaster@owasa.org.

Improvements at the Mason Farm
Wastewater Treatment Plant will enhance
treated water quality, enable reuse

The $50 million upgrade which began at our Mason Farm Wastewater Treatment Plant in 2004 has significantly improved the quality of treated water that we recycle into Morgan Creek. The project is on schedule for completion in mid-2007.

In addition to odor control, standby power and a capacity expansion, our project includes the addition of filters and an ultraviolet (UV) light disinfection system. The filters and UV systems went into full operation in January, 2006.

From January through June, 2006, the UV disinfection system reduced fecal coliform bacteria levels in our treated water to an average of 2 colony forming units per 100 milliliters (CFU/100 mL). Previously we used chlorine for disinfection.

With chlorine disinfection, coliform levels had averaged 24 CFU/100 mL from July through December, 2005, 28 CFU/100 mL in 2004-05 and 45 CFU/100 mL in 2003-04. The regulatory standard for these bacteria is a maximum of 200 CFU/100 mL. As a further comparison, the natural coliform levels in Morgan Creek upstream of our plant ranged from 50 to 1400 CFU/100mL in 2005.

The filters have improved the clarity of our treated water as measured by the level of suspended solid particles (TSS). From January through June, 2006, the TSS levels averaged 2 milligrams per liter (mg/L). This compares to a regulatory TSS limit of 30 mg/L and averages of 5 to 7 mg/L in previous years.

The wastewater treatment improvements will enable use of highly treated or “reclaimed” wastewater for certain non-drinking purposes. OWASA and the University of North Carolina at Chapel Hill are planning a reclaimed water system that will initially serve some chiller plants, where drinking water is now used to cool the air for campus buildings and equipment. The University and other future users will pay for the reclaimed water system and its operating and administrative costs.

To find out more: If you are interested in learning more about wastewater treatment or the reclaimed water system,  please contact us at 968-4421 or send an e-mail to webmaster@owasa.org.

If you are interested in learning more about wastewater treatment, which is a significant form of recycling, please contact us at 968-4421 or webmaster@owasa.org.

Comments or questions?

Whenever you have a comment, request or question about our wastewater management services or facilities, we would like very much to hear from you.

Along with protecting the public health and the environment, one of our highest priorities is being a good neighbor to you and other customers. If you would like to visit or know more about any of our facilities, please contact us.

Please feel free to visit us in our offices, or send us a letter, e-mail or fax at any time. Our addresses, telephone number and other contact information are:

400 Jones Ferry Rd., Carrboro, NC 27510
Telephone: (919) 968-4421 Fax: 968-4464
E-mail: webmaster@owasa.org
Website: www.owasa.org

OWASA operates the community's wastewater system under National Pollution Discharge Elimination System (NPDES) Permit Number NC-0025241. The Division of Water Quality of the North Carolina Department of Environment and Natural Resources administers the standards and regulations that apply to our wastewater management services.