There are two main sources of water pollution; point sources and non-point sources. Point
sources include factories, wastewater treatment facilities, septic systems, and other sources that
are clearly discharging pollutants into water sources. Non-point sources are more difficult to
identify, because they cannot be traced back to a particular location. Non-point sources include
runoff including sediment, fertilizer, chemicals and animal wastes from farms, fields, construction
sites and mines. Landfills can also be a non-point source of pollution, if substances leach from
the landfill into water supplies.
The United States Environmental Protection Agency (EPA) divides water pollution into the
following six categories:
1. Biodegradable waste consists mainly of human and animal waste. When biodegradable
waste enters a water supply, the waste provides an energy source (organic carbon) for
bacteria. Organic carbon is converted to carbon dioxide and water, which can cause
atmospheric pollution and acid rain; this form of pollution is far more widespread and
problematic than other forms of pollutants, such as radioactive waste. If there is a large
supply of organic matter in the water, oxygen-consuming (aerobic) bacteria multiply
quickly, consume all available oxygen, and kill all aquatic life.