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You may think of pollution and contamination as being the same thing. Perhaps in a general term, they are. But when it comes to specifically talking about your water, the two, and their causes are very different.

Pollution is due to the influence or activities of people, where contamination may be natural. There are many specific causes of water pollution, but before we list the toppers, it's important to understand two broad categories of water pollution: “Point source” — occurs when harmful substances are emitted directly into a body of water. “Nonpoint source” — delivers pollutants indirectly through transport or environmental change.

An example of a point source of water pollution is a pipe from an industrial facility discharging effluent directly into a river. An example of a nonpoint-source of water pollution is when fertilizer from a farm field is carried into a stream by rain (i.e. run-off). Point-source pollution is usually monitored and regulated, at least in Western countries, though political factors may complicate how successful efforts are at true pollution control. Nonpoint sources are much more difficult to monitor and control, and today they account for the majority of contaminants in streams and lakes.

There are many sources of water pollution; some being oil spills, pesticides and herbicidal usage and clear-cutting of forestry. But by and large, an annual offender is clearly industrial chemical pollution. Almost all bodies of water in the world have some level of pollution from chemicals and industrial waste. In the United States, 34 billion liters per year (60%) of the most hazardous liquid waste—solvents, heavy metals, and radioactive materials—is injected directly into deep groundwater via thousands of "injection wells."

Although the EPA requires that these effluents be injected below the deepest source of drinking water, some pollutants have already entered underground water supplies in Florida, Texas, Ohio, and Oklahoma. The US is not alone in careless treatment of its groundwater. In the late 1990s, India's Central Pollution Control Board found that groundwater was unfit for drinking in all 22 major industrial zones it surveyed.

On the other hand, water contamination is often used to refer to impurities in water regardless of the source or events that led to the impurities being in the water. A common impurity or contamination in water is its TDS count. Total Dissolved Solids (TDS) consist mainly of carbonates, dissolved bicarbonates, chlorides, sulfates, phosphates, nitrates, calcium, magnesium, sodium, potassium, iron, manganese, and a few others. They do not include gases, colloids, or sediment. The TDS can be estimated by measuring the specific conductance of the water. Dissolved solids in natural waters range from less than 10 mg/l for rain to more than 100,000 mg/l for brines. Since TDS is the sum of all materials dissolved in the water, it has many different mineral sources.

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Turbidity is often a contaminant or impurity of waters. Turbidity is the term given to anything that is suspended in a water supply. It is found in most surface waters, but usually doesn't exist in ground waters except in shallow wells and springs after heavy rains. Turbidity gives the water a cloudy appearance or shows up as dirty sediment. Undissolved materials such as sand, clay, silt or suspended iron contribute to turbidity. Turbidity can cause the staining of sinks and fixtures as well as the discoloring of fabrics. Usually turbidity is measured in NTUs (nephelometric turbidity units). Typical drinking water will have a turbidity level of 0 to 1 NTU. Turbidity can also be measured in ppm (parts per million) and it's size is measured in microns. Turbidity can be particles in the water consisting of finely divided solids, larger than molecules, but not visible by the naked eye; ranging in size from .001 to .150 mm (1 to 150 microns). The US EPA has established an MCL for turbidity to be 0.5 to 1.0 NTU, because it interferes with disinfection of the water.

The treatment for turbidity can be reduced to 75 microns with a cyclone separator, then reduced down to 20 micron with standard backwashable filter, however flow rates of 5 gpm/ sq. ft. are recommended maximum. Turbidity can be reduced to 10 micron with a multimedia filter while providing flow rates of 15 gpm/sq. ft. Cartridge filters of various sizes are also available down into the submicron range. Ultrafiltration also reduces the turbidity levels of process water.

By and large it is the man-made pollutions of waters that get the most attention, and perhaps rightfully so. But what is also important is the overall contamination, or natural quality of water that will help determine the treatments necessary to make a water safe for public consumption.

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