ISO 9439 Ultimate Biodegradability Test for CO2 Evolution

Introduction to  ISO 9439

Testing of biodegradability is critical to understand the behaviour in the environment, in particular for water applications like wastewater treatment and natural environments step one. An ISO standardized test method based on OECD guidelines for measuring the aerobic degradability of chemicals is given by ISO 9439. Inhibition test for ready biodegradability, i.e., rapid and complete mineralization of the substance in the presence of air under standardised conditions. The result means regulatory, environmental, and product development compliance.

ISO 9439  Test Method

ISO 9439  Results and Interpretation

As chemical decomposition occurs primarily via the formation of CO₂ and H₂O, measurements of CO₂ produced during aeration and biodegradation can be used to indicate biodegradation of the test substance. During aeration of the working solution, it is important to use CO₂-free air, which can be produced by using a few NaOH washing bottles to strip CO₂ from the air. Once produced, CO₂-free air can be used to aerate the working solution. While the solution is aerated, the test substance is biodegraded to form CO₂.

The results are interpreted based on the percentage of organic carbon converted to CO_2, with specific criteria for “readily” and “ultimate” biodegradability. 

Tests Related to ISO 9439 

Alternatively, ISO 14593 and ISO 15462 are used for more accurate information on biodegradation rates. ISO 9439 is similar to OECD 301B and ASTM D5864.

Use of ISO 9439  in Various Industries

This test is primarily used by the environmental industry. 

Materials Commonly Tested with ISO 9439 

 This test is suitable for highly soluble, poorly soluble (or even insoluble), and/or absorbing materials.