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Water contamination can come from many different sources. Here is a look at the most common ones:

  1. Runoff

Runoff is now thought by most to be the biggest source of water pollution. (Freeman & Gower, 2011) First, there is the runoff from everyday activities. Have you ever walked by a puddle in a parking lot and noticed the water had a strange iridescent glow to it? This is from all the oil leaks, antifreeze, and whatever else drips from cars onto the pavement being washed away by the rain. In towns and cities, chemical runoff can occur not just from vehicle byproducts but from local businesses (painters, landscape companies, drycleaners, etc.) who use chemicals in their trades. These pollutants run into storm drains and eventually make their way to waterways, where they can reside in the environment for quite some time.

On a much larger scale is the runoff that occurs from agricultural activities. Each year an individual farmer might spray thousands of gallons of pesticides on their field, and other fertilizers and pesticides are ground into the soil. When it rains, it washes away some of this chemical residue, delivering it into waterways and eventually our lakes and oceans. It can also seep down into groundwater supplies. Runoff from animal feedlots is another major source of runoff pollution. As a result, communities in agricultural areas often have the most heavily contaminated water.

  1. Factory wastewater

Factories of all types frequently discharge their wastewater into rivers and streams. Though there are some regulations governing this practice to prevent companies from dumping highly toxic waste, even the allowable levels of chemicals in water that is dumped from factories represents a significant source of water pollution. There are also questions about just how safe this practice is. As Hawken, Lovins and Hunter-Lovins ask, though factories that discharge water waste into rivers often claim it is harmless, “If it’s clean enough for the public to use, why isn’t it clean enough for the factory to use?” (1999, p. 283) There’s also little to no oversight of the practice (it’s not as though EPA officials are at every factory monitoring the discharge) which makes it easy for illegal dumping to occur.

  1. Wastewater from water plants

Ironically enough, water contamination can come from the very facilities we use to clean our water, who often dump concentrated waste back into the river. For example, in Salt Lake City, Utah, state officials settled cases with 4 municipalities who apparently dumped wastewater into rivers and streams. (USA Today, 1-19-2016, p. 8A) The nonprofit U.S. Public Interest Research Group surveyed U.S. water treatment facilities in 2004 and found that more than 60% of them were discharging wastewater that exceeded allowable contaminant limits. (Eilperin, 2004)

  1. Landfills and dumps

These are often a major contributor to groundwater contamination. Dumps often accept barrels of liquid or chemical waste that is then buried in the landfill. If the geography under the dump is porous and the waste improperly secured, these chemicals can seep directly into the groundwater. Even the runoff or seepage from everyday products can contain chemicals that make their way into water supplies.

  1. Fracking operations

Not only can poorly drilled wells or fissures in the rock below deliver fracking fluids and methane directly into groundwater supplies, but many fracking operations dispose of these chemical-laden fluids by pumping them back into the ground.

  1. Mine operations & mine runoff

Mining operations often have retention ponds full of toxic water, and water contamination can often come from runoff from tailings and other rock mined from the earth. These rocks are often rich in contaminants like lead, mercury, or arsenic. Each spring, the melting snow can carry this runoff into streams and rivers, contaminating water supplies. As one resident in Silverton, CO, recalls, “We used to say you had to chew your water instead of drinking it.”

  1. Natural contaminants

Some contaminants, like lead or arsenic, can come from the earth itself. Natural contamination is more likely in groundwater than rivers and lakes, and more likely in private wells, where levels of these contaminants can vary depending on the rock below.

  1. Air pollution & acid rain

Ironically enough, air pollution can be a significant source of water pollution. Every time it rains, the rain can carry whatever chemicals are in the air down to the Earth below. Much of the mercury in fish comes from air pollution. The mercury in the air eventually settles back down into rivers, lakes and oceans, where water-borne bacteria convert it into methylmercury, which is taken up by algae and then makes its way up the food chain.

  1. Mystery pollution

Unfortunately, because chemicals are protected under intellectual property laws, it’s often hard to match the pollutant to polluter. So a lot of the contamination from industrial operations or illegal dumping is simply untraceable.

In review, water pollution comes from a variety of sources:

  • Farming operations
  • Feed lots
  • Industrial factories
  • Landfills
  • Pesticides & fertilizer runoff
  • Acid rain
  • Chemical spills
  • Leaking gas tanks
  • Septic systems
  • Cesspool effluents
  • Air pollution




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