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Water Contamination

Water Contamination
Soil Contamination
How Bioremediation Works
Types of Bioremediation
Alternatives to Bioremediation
Exxon Valdez

     There are essentially two ways contamination occurs.  One is called point source contamination.  For example, an oil spill is a point source contamination, as there is a known, recognizable source responsible for the contamination.   The second way is called non-point source contamination.  This occurs when no obvious, recognizable source of contamination is apparent.  Pesticides washed by rainfall from farmers' fields into nearby rivers is a common example of non-point source contamination.  Here is a list of examples of both types of contamination.

Point sources

  • On-site septic systems
  • Leaky tanks or pipelines containing petroleum products
  • Leaks or spills of industrial chemicals at manufacturing facilities
  • Underground injection wells (industrial waste)
  • Municipal landfills
  • Livestock wastes
  • Leaky sewer lines
  • Chemicals used at wood preservation facilities
  • Mill tailings in mining areas
  • Fly ash from coal-fired power plants
  • Sludge disposal areas at petroleum refineries
  • Land spreading of sewage or sewage sludge
  • Graveyards
  • Road salt storage areas
  • Wells for disposal of liquid wastes
  • Runoff of salt and other chemicals from roads and highways
  • Spills related to highway or railway accidents
  • Coal tar at old coal gasification sites
  • Asphalt production and equipment cleaning sites

Non-point (distributed) sources

  • Fertilizers on agricultural land
  • Pesticides on agricultural land and forests
  • Contaminants in rain, snow, and dry atmospheric fallout

*Note: These sources are taken directly from Environment Canada's website.

     Typically, there are three types of water contamination.  These include agricultrual , industrial , and municipal contamination.  For the purposes of this website, oil spills will be separated from the industrial category and placed into their own category.  This will make four cateories of water contamiation: agricultural, municipal, industrial, and oil spill contamination.   

Agricultural contamination 

     Agricultural contamination refers to the contaminants found in the surface water and/or groundwater as a result of large-scale livestock and poultry farming as well as from farmers' croplands.  A classic example of agricultural contamination is pesticides being washed into rivers and streams by rainfall. 

     Most agricultural contaminants that enter the groundwater are nitrates and pesticides.   Pesticides, designed to protect the farmer's crops from pesky insects, are applied directly to the soil by the farmers.  However, if these pesticides are not applied in the proper conditions or if the field is improperly managed, the pesticides leach through the soil and into the groundwater.  Contamination due to pesticides, although found in almost every American state, occurs much less frequently than nitrate contamination.  Nitrate contamination is much more common because it is very soluble in water.  This means that it can leach through wet or moist soil and into the groundwater very easily. 

     The nitrates that are causing the contamination can come from a number of sources such as: nitrogen rich fertilizers, animal manure, and nitrogen-fixing plants such as legumes.  There are certain conditions that will be more likely to cause a contamination than others.  The most common contamination-causing conditions are:  improper timing of application of fertilizer or manure, excessive fertilizer or manure, and over irrigation.

Crop Spraying
This is a picture of a farmer spraying his crops with pesticides

Municipal Contamination
     Municipal contamination refers to the wastewater that comes from our homes and small businesses.  Due to advanced filtration systems, many of the contaminants are filtered out or broken down before the water is returned to the drinking water supply.  However, these barriers do not stop everything.  Sometimes, a contaminant survives the filtration system and appears in the drinking water.  This contaminant could have originated from almost anywhere.  Take a minute to consider what kinds of things you dump down your sink on a daily basis. 
     A good example of a municipal contamination would be Lake Huron.  Recently, several beaches on Lake Huron were closed due to E. coli contamination.  E. coli is a bacteria that is found in the stomach and intestines of humans and cattle.  When it is found on a beach, that is a good indication that somehow, fecal matter has found its way into the lake water, which raises serious health concerns.  If people were to drink the water containing the e. coli, they would become very sick and could possibly die. 
     The seriousness of e. coli contamination was  demonstrated in Walkerton, Ontario in May 2000.  Filtration of the town's drinking water was improperly managed and as a result, e. coli made its way into the drinking water.  When people drank their tap water as they usually did, they were unknowingly ingesting e. coli bacteria.  By the time it was over, seven people had died and over 2,000 people were sick.  This clearly demonstrates what can happen when the filtration process is neglected.  The best defence against municipal contamination is an up-to-date, carefully monitored water filtration system. 

Water Treatment Facility
This is a picture of a water treatment facility. Here, water is filtered to eliminate contaminants.

Industrial Contamination

     Industrial contamination is any contamination that occurs as a result of the dumping of industrial waste.  An example of industrial contamination occurred in Ville Mercier, Quebec.  Industrial waste was dumped into lagoons in an old gravel pit.  This went on for many years until eventually, water supplies of thousands of surrounding residents were made unusable.  To restore the area to its original condition, water had to be pumped into the area from 10 km away.

     Although awareness has increased, the problem of industrial contamination has been increasing.  This is mainly due to the increase in number and toxicity of the products used in industrial processes.  Most industrial contamination occurs as point source contamination, with the contaminants entering the water through direct discharges.  Most of the industrial contamination that occurs today is a result of dumping toxic wastes and chemicals and raw sewage directly into our lakes and rivers.  There would also be a small amount of contamination produced indirectly through the smoke stacks.  The contaminants would enter the atmosphere and could be carried far away from the factory and fall to the ground with rain. 

Chromium Puddle
Chromium leaked from industrial sites into a parking lot where it mixed with the water. (New Jersey)

Oil Spills
     Click here to view information on oil spills.