Standard Methods: 2130 B:  Turbidity by Nephelometry

  • Summary
  • Analytes
  • Revisions
  • Data and Sites
Official Method Name
2130 B. Nephelometric Method
Current Revision
Standard Methods 19th Edition (1995)
Method Subcategory
Method Source
  Standard Methods
  Standard Methods Online - Standard Methods for the Examination of Water and Wastewater
Brief Method Summary
This method is based on 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 under the same conditions. The higher the intensity of scattered light, the higher the turbidity. Formazin polymer is used as the primary standard reference suspension. The turbidity of a specified concentration of formazin suspension is defined as 4000 NTU.
Scope and Application
Used for surface waters, wastewaters, and drinking water.
Applicable Concentration Range
0 to > 1000 NTU
Turbidity can be determined for any water sample that is free of debris and rapidly settling coarse sediment. Dirty glassware and the presence of air bubbles give false results. "True color", i.e., water color due to dissolved substances that absorb light, causes measured turbidities to be low. This effect usually is not significant in treated water.
Quality Control Requirements
See Section 2020 Quality Assurance/Quality Control.
Sample Handling
Determine turbidity as soon as possible after the sample is taken. Gently agitate all samples before examination to ensure a representative measurement. Sample preservation is not practical; begin analysis promptly. Refrigerate or cool to 4 degrees C, to minimize microbiological decomposition of solids, if storage is required. For best results, measure turbidity immediately without altering the original sample conditions such as temperature or pH.
Maximum Holding Time
48 hours (regulatory)
Relative Cost
$201 to $400
Sample Preparation Methods