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The measurement of turbidity is a key test of both water clarity and water quality. [citation needed] There are two standard units for reporting turbidity: Formazin Nephelometric Units (FNU) from ISO 7027 and Nephelometric Turbidity Units (NTU) from USEPA Method 180.1.
Three glass vials used as turbidity standards for 5, 50, and 500 nephelometric turbidity units (NTU). Turbidity is a measure of the cloudiness of water based on light scattering by particles at a 90-degree angle to the detector. A turbidity sensor is placed in water with a light source and a detector at a 90-degree angle to one another.
[2]: 89–98 Turbidity is a measure of the light scattering ability of suspended matter in the water. [2]: 131–137 Salinity measures water density or conductivity changes caused by dissolved materials. [2]: 99–100
The unit is called Formazin Turbidity Unit (FTU). Nephelometric Turbidity Units (NTU) specified by United States Environmental Protection Agency is a special case of FTU, where a white light source and certain geometrical properties of the measurement apparatus are specified. (Sometimes the alternate form "nephelos turbidity units" is used [7] [8])
The NRCS curve number is related to soil type, soil infiltration capability, land use, and the depth of the seasonal high water table. To account for different soils' ability to infiltrate, NRCS has divided soils into four hydrologic soil groups (HSGs). They are defined as follows. [1]
The retention time is the average time that a particulate remains in the clarifier. The turbidity is a measure of cloudiness. Higher values for turbidity removal efficiency correspond to less particulates remaining in the clarified stream. The settling velocity of a particulate can also be determined by using Stokes' law. [17]
Soil texture is a classification instrument used both in the field and laboratory to determine soil classes based on their physical texture. Soil texture can be determined using qualitative methods such as texture by feel, and quantitative methods such as the hydrometer method based on Stokes' law .
In soil science, soil gradation is a classification of a coarse-grained soil that ranks the soil based on the different particle sizes contained in the soil. [1] Soil gradation is an important aspect of soil mechanics and geotechnical engineering because it is an indicator of other engineering properties such as compressibility , shear strength ...