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Encyclopedia > Turbidity
Turbidity standards of 5, 50, and 500 NTU
Turbidity standards of 5, 50, and 500 NTU

Turbidity is a cloudiness or haziness of a fluid, or of air, caused by individual particles (suspended solids) that are generally invisible to the naked eye, similar to smoke in air. turbidity standards. ... Particle (ecology) is the term for small objects of nonbiological kind. ... Total suspended solids is a water quality measurement usually abbreviated TSS. This parameter was at one time called non-filterable residue (NFR), a term that refers to the identical measurement: the dry-weight of particles trapped by a filter, typically of a specified pore size. ... The naked eye is a figure of speech referring to human visual perception that is unaided by enhancing equipment, such as a telescope or binoculars. ... This article does not cite any references or sources. ... Look up air in Wiktionary, the free dictionary. ...

Turbidity in open water is often caused by phytoplankton and the measurement of turbidity is a key test of water quality. The higher the turbidity, the higher the risk of the drinkers developing gastrointestinal diseases, especially for immune-compromised people, because contaminants like virus or bacteria can become attached to the suspended solid. The suspended solids interfere with water disinfection with chlorine because the particles act as shields for the virus and bacteria. Similarly suspended solids can protect bacteria from UV sterilisation of water. Diagrams of some typical phytoplankton Phytoplankton are the autotrophic component of plankton. ... Water quality is the physical, chemical and biological characteristics of water, characterized through the methods of hydrometry. ... All diseases that pertain to the gastrointestinal tract are labelled as digestive diseases. ... General Name, symbol, number chlorine, Cl, 17 Chemical series halogens Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ...

Fluids can contain suspended solid matter consisting of particles of many different sizes. While some suspended material will be large enough and heavy enough to settle rapidly to the bottom container if a liquid sample is left to stand (the settleable solids), very small particles will settle only very slowly or not at all if the sample is regularly agitated or the particles are colloidal. These small solid particles cause the liquid to appear turbid. Settling is the process by which particulates settle to the bottom of a liquid and form a sediment. ... A Colloid or colloidal dispersion is a type of homogeneous mixture. ...


Measurements of turbidity

Turbid creek water caused by heavy rains.
Turbid creek water caused by heavy rains.

The most widely used measurement unit for turbidity is the FTU (Formazin Turbidity Unit). ISO refers to its units as FNU (Formazin Nephelometric Units). Image File history File links Size of this preview: 800 × 600 pixelsFull resolution (2938 × 2203 pixel, file size: 2. ... Image File history File links Size of this preview: 800 × 600 pixelsFull resolution (2938 × 2203 pixel, file size: 2. ...

There are several practical ways of checking water quality, the most direct being some measure of attenuation (that is, reduction in strength) of light as it passes through a sample column of water. The alternatively used Jackson Candle method (units: Jackson Turbidity Unit or JTU) is essentially the inverse measure of the length of a column of water needed to completely obscure a candle flame viewed through it. The more water needed (the longer the water column), the clearer the water. Of course water alone produces some attenuation, and any substances dissolved in the water that produce color can attenuate some wavelengths. Modern instruments do not use candles, but this approach of attenuation of a light beam through a column of water should be calibrated and reported in JTUs. This article is about Physics. ...

A property of the particles — that they will scatter a light beam focused on them — is considered a more meaningful measure of turbidity in water. Turbidity measured this way uses an instrument called a nephelometer with the detector setup to the side of the light beam. More light reaches the detector if there are lots of small particles scattering the source beam than if there are few. The units of turbidity from a calibrated nephelometer are called Nephelometric Turbidity Units (NTU). To some extent, how much light reflects for a given amount of particulates is dependent upon properties of the particles like their shape, color, and reflectivity. For this reason (and the reason that heavier particles settle quickly and do not contribute to a turbidity reading), a correlation between turbidity and TSS is somewhat unique for each location or situation. A nephelometer is an instrument for measuring suspended particulates in a liquid. ... Total suspended solids is a water quality measurement usually abbreviated TSS. This parameter was at one time called non-filterable residue (NFR), a term that refers to the identical measurement: the dry-weight of particles trapped by a filter, typically of a specified pore size. ...

Turbidity in lakes, reservoirs, and the ocean can be measured using a Secchi disk. This black and white disk is lowered into the water until it can no longer be seen; the depth (Secchi depth) is then recorded as a measure of the transparency of the water (inversely related to turbidity). The Secchi disk has the advantages of integrating turbidity over depth (where variable turbidity layers are present), being quick and easy to use, and inexpensive. It can provide a rough indication of the depth of the euphotic zone with a 3-fold division of the Secchi depth. However, this can be used in shallow waters where the disk can still be seen on the bottom. Secchi disk pattern Created in 1865 by Pietro Angelo Secchi, the Secchi disk is a device used to measure water transparency in open waters of lakes, bays, and the ocean. ... The euphotic zone is the surface layer of the ocean where sufficient light is available for photosynthesis. ...

Turbidity normally increases after heavy rain. The rain runs along the ground picking up small particles of dirt before emptying into water sources, hence increasing turbidity levels. These increased levels can harm the fish that live in them. The fish can stop eating, cough, and have reduced growth rates, in high turbid areas, until they eventually die.

Turbidity in air, which causes solar beam attenuation, is used as a measure of pollution. To model the attenuation of beam irradiance, several turbidity parameters have been introduced, including the Linke turbidity factor (TL)[1].


There are frequently standards on the allowable turbidity in drinking water. In the United States (as of 2003) the allowable standard is 1 NTU, with many drinking water utilities striving to achieve levels as low as 0.1 NTU.

  • ISO 7027 "Water Quality: Determination of Turbidity" [2]
  • US EPA 180.1 "Turbidity"[3]

For many mangrove areas, turbidity is needed to be high. For most mangroves along the eastern Coast of Australia, in particular Moreton Bay, turbidity is necessary to be as high as 6NTU. Above and below water view at the edge of the mangal. ... The foreshore at Manly. ...

See also

In microbiology, McFarland standards are used as a reference to adjust the turbidity of bacterial suspensions so that the number of bacteria will be within a given range. ... Control room and schematics of the water purification plant to Bret lake. ...

External links


  1. ^ http://www.helioclim.net/linke
  2. ^ http://www.iso.org/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=30123
  3. ^ http://www.umass.edu/tei/mwwp/acrobat/epa180_1turbidity.pdf

  Results from FactBites:
OzEstuaries; Coastal Indicators - Turbidity (1248 words)
Turbidity is a measure of water clarity or murkiness.
The turbidity maximum often occurs in the vicinity of the 2 ppt isohaline [11], and migrates in response to changes in freshwater inflow (see Figure 2).
Turbidity is estimated either by nephelometry or by directly determining the mass of suspended particulate matter in a given volume of sample.
  More results at FactBites »



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