WATER QUALITY
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To most people not professionally involved in water quality issues, water is either drinkable (or potable) or contains potentially harmful or toxic substances (suffering from water pollution). However, the vast majority of surface water on the planet is neither potable nor toxic. This remains true even if sea water in the oceans (which is too salty to drink) isn't counted. Another general perception of water quality is that of a simple property that tells whether water is polluted or not. In fact, water quality is a very complex subject, in part because water is a complex medium intrinsically tied to the ecology of the planet.
Overview
Contaminants that may be in untreated water include microorganisms such as viruses and bacteria; inorganic contaminants such as salts and metals; pesticides and herbicides; organic chemical contaminants from industrial processes and petroleum use; and radioactive contaminants. Water quality depends on the local geology and ecosystem, as well as human uses such as sewage dispersion, industrial pollution, use of bodies water as a heat sink, and overuse (which may lower the level of the water).
In the United States, the Environmental Protection Agency prescribes regulations that limit the amount of certain contaminants in the water provided by public water systems for tap water. Food and Drug Administration (FDA) regulations establish limits for contaminants in bottled water that must provide the same protection for public health. Drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. The presence of these contaminants does not necessarily indicate that the water poses a health risk.
Some people use water purification technology to remove contaminants from the municipal water supply they get in their homes, or from local pumps or bodies of water. For people who get water from a local stream, lake, or groundwater, their drinking water is not filtered by the local government.
Toxic substances and high populations of certain microorganisms can present a health hazard for non-drinking purposes such as irrigation, swimming, fishing, rafting, boating, and industrial uses. These conditions may also impact wildlife which use the water for drinking or as a habitat.
Interest by individuals and volunteer groups in making local water quality observations is high, and an understanding of the basic chemistry of many water quality parameters is an essential first step to making good measurements. Most citizens harbor great concern over the purity of their drinking water, but there is far more to water quality than water treatment for human consumption.
Statements to the effect that "uses must be preserved" are included within water quality regulations because they provide for broad interpretation of water quality results, while preserving the ultimate goal of the regulations. Technical measures of water quality—that is, the values obtained when making water quality measurements—are always subject to interpretation from multiple perspectives. Is it reasonable to expect a river to be pristine in a landscape that no longer is? If a river has always carried sediment, is it polluted even if the cause is not man induced? Can water quality be maintained when water quantity can not? The questions that arise from consideration of water quality relative to human uses of the water become more complex when consideration must be given to conditions required to sustain aquatic biota. Yet inherent in the concept of preserving uses is a mandate that waterways must be much more than conduits for a fluid we might want to drink, fill our swimming pool with, or carry our wastes out of town.
Measurement of water quality
The complexity of water quality as a subject is reflected in the many types of measurements of water and wastewater quality. These measurements include (from simple and basic to more complex):
The simple measurements (towards the top in the listing above) are those that can be made with an instrument, in most cases in the field (in situ). The more complex or difficult measurements are those that come from analytical methods, typically requiring a water sample to be collected, preserved, and later analyzed in a laboratory setting. These latter measurements can be expensive and it is always important to understand in advance the reason(s) for making any particular measurement. Also, because the number of substances that could be present in a water sample runs to the millions, it is not possible to reasonably establish what all might be in a particular sample without a very large budget. If the logic of this fact is difficult to grasp, the inefficiency should be obvious: to satisfy such a request, a laboratory would have to charge for determining the more that 99% of possibilities that are NOT present in the sample to discover the minutely less than 1% that are.
One effective way to improve water quality is to get more oxygen in the water. Aeration is often done by sending compressed air to an air diffuser at the bottom of the pond. The deep water rises to the surface and the water molecules grab oxygen from the atmosphere. As the pond water circulates, soon the oxygen levels in the water from top to bottom increase. Thus, aeration adds oxygen to the water and improves water quality.
See also
External links
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