Pollutants can come from one source or a myriad of sources. Usually, if pollutants come from one source into that water body, such as factory waste disposal, it is called point source pollution.

For example, during meat processing in a slaughterhouse, high volumes of water may be used making it a significant point source of pollution to local water bodies, ecosystems, and communities.

On the other hand, if pollution comes from many sources, it is called nonpoint source pollution.

Nonpoint pollution is when water is chemically modified from natural and human-made pollutants as runoff, drainage, seepage or rainwater interacts with such pollutants. Think of it in this scenario:

Imagine that crop farmers in a region have used chemicals for a while. The lands, therefore, have the residue of the chemicals. After a while, rains, runoff, surface water, and seepage will carry and deposit the chemicals into watersheds through lakes, rivers, wetlands, coastal waters, and even our underground sources of drinking water.

In many of the states in the USA, there are reports that nonpoint source pollution is the leading remaining cause of water quality problems. These reports may not be unique to the USA alone, and likely a similar scenario would be so in many other developed countries.

Nonpoint source pollution can include:

• Excess of fertilizers, herbicides, insecticides, and chemical applications from agricultural lands and residential areas
• Oil, grease, and toxic substances from energy plants and municipal runoff.
• Debris and sediment from construction sites, farms, and forest lands.
• Acid drainage from abandoned mines.
• Waste, bacteria, and nutrients from animals, waste from pets as well as faulty septic tanks.
• Chemical/particle deposits from the atmosphere and hydromodification.