Wastewater Collection
and Treatment

2004-05 Annual Report

Highly treated or "reclaimed" wasterwater is released into
Morgan Creek in southeast Chapel Hill.

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 9,000 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 2004-05

The volume of the overflows (listed below) in 2004-05 equaled 0.003% of the 2.983 billion gallons of wastewater collected in the wastewater system.

Typical cause(s) of wastewater spills

Grease enters sewers from residences and businesses. The grease hardens and causes blockages.

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

Debris or trash in sewers blocks the flow of wastewater.

A pipe may break due to settling of soil beneath it.

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.

Inspect and clear sewers with cutting and flushing equipment; educate customers about proper grease disposal.

Clear sewer easements to keep roots from growing into sewers; limit plantings allowed along easements.

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 mains;

increased inspections or other maintenance;

repair, renovation or replacement of pipes; and

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

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

In 2004-05, OWASA crews cleared and cleaned 179 miles or 60% of our 296-mile network of sewers. This work helps reduce wastewater overflows by removing roots, grease, etc. before they block pipes.

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

On May 2 and 3, 2005 the level of CBOD (please see definition above) in our treated wastewater exceeded the limit for unknown reasons.

No fish kills or other significant downstream impacts from the noncompliance event are known to have resulted.

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

In May, 2004, OWASA began a three-year, $50 million improvement project at the Mason Farm Wastewater Treatment Plant on the southeast side of Chapel Hill . Above: The new filter structure under construction at the Mason Farm Wastewater Treatment Plant. The filters will be filled with sand to a depth of six feet.

This project will:

Improve the quality of our treated wastewater by adding filters and an ultraviolet light disinfection system. The filters will further clean the treated water and reduce the level of nitrogen in treated water. Nitrogen is a nutrient which encourages the growth of algae in lakes.

Improve the quality of water in Morgan Creek and Jordan Lake , which is downstream of our plant. Jordan Lake is a water source for several communities in the region.

Enable reuse of highly treated or “reclaimed” wastewater for certain non-drinking purposes. OWASA and the University of North Carolina at Chapel Hill are planning a water reuse system that will initially serve some chiller plants that cool the air for campus buildings. (The University and other future users will pay for the reuse system and its operation.)

Eliminate off-site odors, which have affected nearby neighborhoods and facilities in the past. Odor improvements to be completed by November, 2005 are expected to be successful, but we will work with the community to further evaluate the need for additional odor-related work.

Expand the plant's capacity from 12 to 14.5 million gallons per day and increase our ability to handle high wastewater flows due to wet weather.

Add a second large generator to help ensure the plant will have adequate back-up power during storms, etc. affecting our normal power supplies.

Questions or comments?

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.

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 untreated 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 through 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 537-4424 or send an e-mail to 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.