Leck Mitchell: Mitchell Method M5331: Turbidity of Water by LED Nephelometry
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Official Method Name
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Determination of Turbidity by LED Nephelometry |
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Current Revision
| Revision 1.1, March 2009 |
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Media
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WATER |
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Instrumentation
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Nephelometer |
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Method Subcategory
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Physical |
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Method Source
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Citation
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Mitchell Method M5331, Revision 1.1. ``Determination of Turbidity by LED Nephelometry,'' March 5, 2009. Available at http://www.nemi.gov or from Leck Mitchell, PhD, PE, 656 Independence Valley Dr., Grand Junction, CO 81507. |
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Brief Method Summary
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The method is based upon a comparison of the intensity of light scattered by the sample under defined conditions, with the intensity of light scattered by a standard reference suspension. The higher the intensity of scattered light, the higher the turbidity. Readings in NTUs are made using a laser nephelometer designed according to specifications given in section 6.1 and 6.2. Primary standard suspensions are used to calibrate the instrument. A secondary standard is monitored periodically for deterioration using one of the primary standards. |
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Scope and Application
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This method covers the determination of turbidity in drinking, ground, surface and any colorless water with a turbidity of less than 40 NTU.This method can be used for compliance monitoring and reporting under the Safe Drinking Water Act (SDWA). |
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Applicable Concentration Range
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The applicable range is 0 to 40 NTU but can be extended by dilution of the sample. |
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Interferences
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The presence of floating debris and coarse sediments that settle out rapidly will give low readings. Finely divided air bubbles can cause high readings. The presence of true color, that is the color of water that is due to dissolved substances that absorb light, will cause turbidities to be low, although this effect is generally not significant with drinking water. Light-absorbing materials such as activated carbon in significant concentrations can cause low readings. |
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Quality Control Requirements
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The minimum requirements of this program consist of an initial demonstration of laboratory capability and analysis of laboratory reagent blanks and other solutions as a continuing check on performance. The laboratory is required to maintain performance records that define the quality of data generated. |
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Sample Handling
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Online instrumentation does not require sample cooling, preservation or storage. |
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Maximum Holding Time
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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