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ASTM D6731 - Biodegradability Test of Lubricant - Oxygen Consumption (ISO/IEC 17025:2017 Accredited)

ASTM D6731 is an aqueous aerobic biodegradability test that determines the biodegradability of lubricants or their components by measuring oxygen consumption during biodegradation in closed respirometers (closed bottles with headspace).

ASTM D6731 Key Summary

Similar to the OECD 301F Closed Respirometer Test, ASTM D6731 measures oxygen consumption to reflect the biodegradation of fully formulated lubricants or their components, based on the exposure to activated sludge from municipal wastewater treatment plant as the inoculum under laboratory conditions.

It has the highest applicability among all other methods and can handle materials that are highly soluble, poorly soluble, insoluble, volatile, involatile, and/or adsorbing. Good dispersion with continuous mixing is usually required for better performance.

Test substances that achieve high levels of biodegradation are assumed to be easily biodegradable in most aerobic aquatic environments.

Requirement and Applicability

Different testing methods are applicable for materials with different properties. Below is a summary of the applicability of ASTM D6731. Please check our Method Selection Guide to select the most appropriate method for your materials. You can also find the applicability for many other methods on Aropha Resource Center

TestAnalytical methodSample info required *Poorly solubleVolatileAdsorbing
ASTM D6731 (Closed respirometer test)
Oxygen consumptionThOD or COD *++/-+

*"Sample info required" is the information needed to calculate the biodegradation percentages. This must be available for a selected method.
*"ThOD" can be easily calculated based on the formula of the sample. Try our Online ThOD Calculator.
*"COD" can be used as an alternative to ThOD if the formula of the material is unknown. We provide COD analysis at Aropha.

Aropha Resource Center

To learn more about different types of biodegradation tests, their applicability, biodegradation mechanisms, and many other information such as case studies, publications, and blogs, please check our Aropha Resource Center

Aropha resource center


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