Manufacturers and farmers throughout the world discharge pollutants into hydrologic systems. Industrial water pollution arises from agricultural practices, deforestation and poor land management. In addition, industrial accidents such as oil or chemical spills can create large-scale disruptions to hydrologic systems. Commercial mining operations may also pollute both surface water and aquifers. Thermal water pollution may occur from industrial processes that discharge heated water.
Undesirable agricultural practices are a major source of industrial water pollution. This type of pollution occurs when rainfall or irrigation causes runoff from farm fields. The runoff often carries with it significant quantities of organic material, as well as chemical fertilizers and pesticides. As a result, these pollutants end up in estuaries and streams.
Industrial processes that discharge wastewater into streams and rivers may pollute bodies of both fresh water and salt water. This effluent may carry industrial water pollution for many nautical miles, affecting marine wildlife. Heavy metals may be contained in some industrial waste. These metals, such as mercury, lead, or beryllium, may settle on the bottom of streams and tidal basins.
Removal of these containments may be very difficult, as disturbing the sediment can result in increasing the risk of human and animal exposure to toxic metals. Regulations may be in place to penalize such activities; however, scofflaws often take advantage of poor enforcement. In many places around the world, illegal dumping of hazardous waste is all too common.
Industrial accidents may result in extremely large releases of industrial water pollution. A noteworthy example is the Deep Horizon oil spill that occurred off the Louisiana Coast in the U.S. in 2010, which was the largest oil spill in U.S. history. A more devastating accident that resulted in long-term industrial water pollution was the Union Carbide gas leak in Bhopal, India in 1984. The accident resulted not only in many deaths and injuries, but also in pollution of groundwater.
Commercial mining, historically, has resulted in toxic metal contamination into both surface and ground water. In the U.S., a uranium mine in Washington State ceased production in 1981, yet 30 years later, residents in the area were experiencing higher levels of poor health that some experts attributed to the open pit uranium mining. Sludge in the bottom of a lake near the mining area was still highly radioactive decades later.
Thermal pollution is another facet of industrial water pollution. This occurs when heated industrial effluent, released into streams or estuaries, raises the ambient water temperature, affecting wildlife. Nuclear reactors are one such source of thermal pollution, as the design of some nuclear power plants circulates oceanic water to maintain the plant's thermal efficiency.