Wastewater Sources

Point Source

Point source water pollution refers to contaminants that enter a waterway from a single, identifiable source, such as a pipe or ditch. Examples of sources in this category include discharges from a factory, a sewage treatment plant or a publicly owned treatment works (POTWs), or a city storm drain. The US Clean Water Act (CWA) defines point source for regulatory enforcement purposes (United States Code Clean Water Act Section 502 (14) 33 U.S.S 1362(14) 1999). The CWA definition of point source was amended in 1987 to include municipal storm sewer systems, as well as industrial storm water, such as from construction sites.

Nonpoint Source

Nonpoint source (NPS) pollution refers to diffuse contamination that does not originate from a single discrete source. NPS pollution is often the cumulative effect of small amounts of contaminants gathered from a large area. A common example is the leaching out of nitrogen compounds from fertilized agricultural lands (Moss 2008). Nutrient runoff in storm water from “sheet flow” over an agricultural field or a forest is also cited as examples of NPS pollution.

Contaminated storm water washed off of parking lots, roads and highways, called urban runoff, is sometimes included under the category of NPS pollution. However, because this runoff is typically channeled into storm drain systems and discharged through pipes to local surface waters, it becomes a point source.

Fugitive emissions are also NPS pollution in that the emissions of gases or vapors take place from pressurized equipment due to leaks and other unintended or irregular releases of gases, mostly from industrial activities. As well as the economic cost of lost commodities, fugitive emissions contribute to air pollution and climate change.