10-12-2012, 01:07 PM
WATER POLLUTION
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Water is a unique substance, because it can naturally renew and cleanse itself, by allowing pollutants to settle out (through the process of sedimentation) or break down, or by diluting the pollutants to a point where they are not in harmful concentrations. However, this natural process takes time, and is difficult when excessive quantities of harmful contaminants are added to the water. And humans are using more and more materials that are polluting the water sources that we drink from. In nine of the last ten years, large blue-green algae blooms have appeared on the northern part of Lake Winnipeg. These are caused by excess phosphorus in the water. Fertilizer use is 15 times higher today than it was in 1945. Beach closures are becoming increasingly common. The list of pollutants is long and the signs of water pollution surround us, but the point is this: we are dumping contaminants into the small portion of water on the planet that is fit for drinking.
What is pollution?
Pollution can be defined in several ways. Water pollution occurs when energy and other materials are released, degrading the quality of the water for other users. Water pollution includes all of the waste materials that cannot be naturally broken down by water. In other words, anything that is added to the water, above and beyond its capacity to break it down, is pollution. Pollution, in certain circumstances, can be caused by nature itself, such as when water flows through soils with high acidities. But more often that not, human actions are responsible for the pollutants that enter the water.
Where is all of this pollution coming from?
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.
How bad is water pollution in Canada?
It is difficult, or impossible, to estimate the amount of water pollution that originates in Canada, because many pollutants come from non-point sources. As well, because all of the water in the world is connected, it is sometimes impossible to tell where the pollutants originated. However, here are a few statistics about North America and Canada:
It is estimated that five million tonnes of road salt are used in Canada each year.
Fertilizer use is more than 15 times what it was in 1945.
In the United States, over 7.5 trillion litres of water are filtered each year to remove silt.
Canadians are the second highest consumers of water, second only to Americans.
Over 360 chemical compounds, including lead, DDT and mercury, have been identified in the Great Lakes.
Between 1950 and 1975, Lake Erie experienced the process of eutrophication, due to excess phosphorus and nitrogen. Without human pollution, the process that took 25 years would have taken 15,000 years!
Some 70,000 commercial and industrial compounds are currently in use in Canada, and there are estimated 1,000 chemicals that are introduced each year.
Just one drop of many household chemicals can render large amounts of water undrinkable; for example, one drop of 2,4-D (a common household herbicide) can make 10 million litres of unfit for drinking!
What impact does domestic waste have on water pollution?
The categories of water pollution that domestic waste fits into are biodegradable waste, hazardous and toxic chemical pollutants and PPCPs. Generally, wastewater treatment facilities are equipped to effectively remove harmful substances generated from biodegradable waste. The hazardous and toxic chemicals that individuals release into the environment are more dangerous (and more preventable). Chemicals, such as cleaners, dyes, paints, pesticides and solvents, which are poured down drains, are a substantial and dangerous form of pollution. Wastewater treatment facilities are generally unequipped to remove PPCPs from wastewater; water pollution from PPCPs is a growing concern. For more information about dangerous pollutants that are found in domestic products, see the Emerging Contaminants fact sheet.
What impact does agriculture have on water pollution?
The greatest agricultural contributions to water pollution are through nutrient and sediment pollution. Livestock waste and fertilizers contain nitrogen and phosphorus, which, if carried to lakes and streams through runoff, can cause significant problems resulting in excess algae growth.
In the last ten years, the number of livestock in Manitoba has increased by about 65 percent, mostly in the form of pigs and cows. The livestock produce a large amount of waste, which many farmers use as fertilizer on their fields. In the Winnipeg area, thousands of hectares of farmland have been designed for efficient runoff, which minimizes flooding. However, when the water runs off, it carries organic matter from the fertilizers straight into the creeks that feed Lake Winnipeg. Agricultural practices in Manitoba are estimated to be responsible for about 17 percent of the phosphorus problem in Lake Winnipeg. There are several best management practices that can reduce the amount of agricultural water pollution, such as collecting animal wastes in a lagoon, or spraying pesticides in small amounts and at minimal runoff times.