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Publicly Owned Treatment Works: Background and Overview
Table of Contents
Background and Overview
P2 Opportunities
Reasons for Change
Complete List of Links

Essential Links:

American Water Works Association
Association for water treatment professionals.

Association of State and Interstate Water Pollution Control Administrators (ASIWPCA).
Association for water pollution control professionals.

City of Superior
Information on P2 for mercury, stormwater, e-waste, batteries and many more issues from the POTW for...

Publicly owned treatment works (POTWs) are municipal wastewater treatment facilities responsible for handling local water supplies. POTWs receive and treat sewage and/or wastewater from residences, commercial activities, and industries. There are POTWs that primarily treat wastewater from industrial users. As the planet becomes more urbanized and industrialized, POTWs are facing the challenges of municipal growth, newly regulated pollutants, more stringent effluent limits, and system overloads. More and more industries are discharging their wastewaters, with or without pretreatment, into sewers servicing POTWs.

Water utilities provide over 100 gallons of fresh, treated water every day for each person in this country, or about 40 billion gallons per day nationwide. Water is collected from various sources such as rivers, lakes, and wells. After collection, water is filtered, treated, and sold for residential, industrial, commercial, and public use. Depending on the population served by the water system, the utility may be a small plant in a rural area that requires the occasional monitoring of a single operator or a huge system of reservoirs, dams, pipelines, and treatment plants, requiring the coordinated efforts of hundreds of people.

The collection, treatment and distribution of water is one of the largest and most expensive tasks of local government. Water supply systems vary from community to community depending on various factors such as the source of water, age and infrastructure integrity, size and population of community, and the needs of the population.

According to the E.P.A., there are approximately 16,000 POTWs nationwide. There are also an estimated 100,000 major pumping stations, 600,000 miles of sanitary sewers, 200,000 miles of storm sewers treating more than 32 billion gallons of wastewater daily. POTWs range in size from <0.1 million gallons treated per day (MGD) to >500 MGD. However, the majority of these facilities (~80 percent) are 1 MGD or less.

The NAICS code for POTWs is 221310. Additional NAICS codes related to water treatment are: Water treatment equipment, manufacturing (NAICS 333319), Water treatment equipment, industrial, merchant wholesalers (NAICS 423830), Water treatment equipment, municipal, merchant wholesalers (NAICS 423850), and Water treatment plant construction (NAICS 237110). There are two SIC codes listed for water treatment: Water treatment construction – general contractor (SIC 1629) and Water treatment equipment, industrial (SIC 3589).

A unique feature of the utilities industry is that urban areas with many inhabitants generally have relatively few utility companies. For instance, there were about 54,000 community water systems in the United States in 2000 serving roughly 264 million people. The 45,900 small water systems served only 26 million people while the 8,100 largest systems served almost 238 million. Alaska, with a 2000 population about 10 percent of that of Massachusetts, had about 3 times more electric generating plants than Massachusetts. These examples show that economies of scale in the utilities industry allow one or two large companies to serve large numbers of customers in metropolitan areas more efficiently than many smaller companies.

According to the U.S. Department of Labor’s Bureau of Labor Statistics, public utilities employed about 851,000 workers in 2000. Electric services provided about 42 percent of all jobs, as shown in table 1.

Table 1. Distribution of wage and salary employment in nongovernment public utlities, 2000
(Employment in thousands)
Total, all utilities
Electric services
Water supply and sanitary services
Combination utility services
Gas production and distribution

Furthermore, although electric utilities are among the biggest customers of natural gas utilities, the processes used to produce their services are largely unrelated. This diversity of production processes is reflected in the size of the establishments that make up the utilities industry. The combination utility industry consists of relatively large plants. In 2000, it accounted for less than 7 percent of the reporting establishments, yet employed an average of more than 90 workers per establishment. On the other hand, water supply utilities accounted for 16 percent of workplaces, yet employed only an average of 8 workers per establishment (table 2).

Table 2. Nongovernment establishments in electric, gas, and sanitary services and average employment per establishment, 2000
Number of
Emplyments per
Total, all utilities
25, 369
Sanitary services
Electric services
Gas production and
Water supply
Combination utility services
Irrigation systems
Steam and air-conditioning

Although many establishments are small, almost half of public utility workers are employed in establishments with 250 or more workers.

In the thirty years since the passage of the Clean Water Act, significant progress has been made towards its primary goals of “swimmable and fishable” waterways and “zero discharge” into our waterways. In 1972 60-70% of our waters were not swimmable or fishable, while in 2002 the numbers had dropped to 39% of rivers, 45% of lakes, and 51% of estuaries. The number of Americans served by sewage treatment facilities doubled during that same period. However, problems persist, particularly in our estuaries. Between 1994 and 2002 the percentage of estuaries that were deemed unsafe rose from 37% to 51%.

According to Albert Slap of the University of Cincinnati College of Law, Sanitary Sewer Overflows (SSOs) and Combined Sewer Overflows (CSOs) cause or contribute to violations of Water Quality Standards in many states, especially those for fecal contamination in waterways. Municipal pollution, and specifically fecal pollution – keeps many areas from meeting clean water standards.

Typical wastes associated with the water supply are:

  • Solvent cleaners and paints, mercury switches and lamps, lubricants and other wastes from
    operations and facility maintenance activities.
  • Disinfection by-products, i.e. trihalomethanes.
  • Corrosion by-products.
  • Leaking or broken lead from service lines, goose neck or service connections.
  • Radon in wells.
  • Pesticides and herbicides rinse waters and containers.
  • Industrial, commercial and household chemical discharges.
  • Mercury
  • Fecal coliform bacteria

Municipalities are constantly searching for options when addressing these challenges. Generally speaking, municipalities have two alternatives available:

  • Expand current POTW facilities to meet the increased demand and/or build
    additional POTWs
  • Initiate a Pollution Prevention (P2) program

The EPA encourages municipalities to address these challenges through pollution prevention programs, as opposed to expansion of existing POTWs or building new POTWs. There are a variety of pollution prevention programs for POTWs, but the focus of this topic hub is:

Industrial pretreatment programs designed to reduce the toxicity of the waste stream

The National Pretreatment Program is a cooperative effort of federal, state, and local regulatory environmental agencies established to protect water quality. The program is designed to reduce the level of pollutants discharged by industry and other non-domestic wastewater sources into municipal sewer systems, and thereby, reduce the amount of pollutants released into the environment through wastewater. The objectives of the program are to protect the Publicly Owned Treatment Works (POTW) from pollutants that may interfere with plant operation to prevent pollutants that may pass through untreated from being introduced into the POTW, and to improve opportunities for the POTW to reuse wastewater and sludge that are generated. The term "pretreatment" refers to the requirement that nondomestic sources discharging wastewater to POTWs control their discharges, and meet limits established by EPA, the State or local authority on the amount of pollutants allowed to be discharged. The control of the pollutants may necessitate treatment prior to discharge to the POTW (therefore the term "pretreatment"). Limits may be met by the nondomestic source through pollution prevention techniques (product substitution recycle and reuse of materials) or treatment of the wastewater.

Program objectives are:

  • To prevent industrial facilities' pollutant discharges from passing through
    municipal wastewater treatment plants untreated;
  • To protect treatment plants from the threat posed by untreated industrial
    wastewater, including explosion, fire, and interference with the treatment
    process; and
  • To improve the quality of effluents and sludge so that they can be used for
    beneficial purposes.

There are more than 1500 publicly owned treatment works that are required to implement local Pretreatment programs. By reducing the level of pollutants discharged by industry into municipal sewage systems, the program ensures the protection of America's multi-billion dollar public investment in treatment infrastructure.

Environmental Health and Safety On-line. Waste Water Pretreatment Information and
Guidance. Available on-line:

EPA, Office of Air Quality Planning and Standards, Emission Standards Division.
“Presumptive MACT for Publicly Owned Treatment Works.” June 8, 1995.s
U.S. Department of Labor, Bureau of Labor Statistics,

Pacific Northwest Pollution Prevention Resource Center.

Slap, Albert J. Adjunct Professor at Law. University of Cincinnati College of Law.
“Wet Weather Public Sewer Issues Under Federal Clean Water Act.”

Water Environment Federation, 601 Wythe St., Alexandria, VA 22314-1994.




The Topic Hub™ is a product of the Pollution Prevention Resource Exchange (P2Rx)

The Publicly Owned Treatment Works Topic Hub™ was developed by:

Southwest Network for Zero Waste
Southwest Network for Zero Waste
Contact email:

Hub Last Updated: 5/22/2007