Method 180.1

Turbidity by Nephelometric

This method is for the determination of turbidity in drinking, ground, surface, and saline waters, domestic and industrial wastes.  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 NTU's (nephelometric turbidity units), are made in a nephelometer.

The applicable range of the method is 0-40 nephelometric turbidity units (NTU).  Higher values may be obtained with dilution of the sample.  Formazin polymer is used as the turbidity reference suspension for water because it is more reproducible than other types of standards previously used for turbidity standards.

The presence of floating debris and coarse sediments which settle out rapidly will give low readings.  Finely divided air bubbles can cause high readings.  The presence of true color (color of water due to dissolved substances that absorb light) will cause turbidities to be low.  Light absorbing materials such as activated carbon in significant concentrations can cause low readings.

(EPA: Office of Water)


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Method Data

Hold Times, Preservatives, Preps, Collection, Analytical & Documentation
Holding Time:   48 hours from sample collection to analysis if samples are kept 4°C.
Preservatives:   Cool sample to 4°C. No chemical preservation is required.
Required Preps:   250mL Plastic or glass bottle with Teflon-lined lid
Collection Method:   Grab sampling
Analytical Methodology:   Nephelometer
Documentation:   180.1

Analyte List*

Analyte Formula CAS Number Detection Limit

* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.