Last updated 26th May 2025

OECD 302B Inherent Biodegradability – Zahn-Wellens Test

The OECD 302B test for inherent biodegradability determines inherent biodegradability. A sample of the substance is placed in a test vessel containing activated sludge at controlled test conditions (aerobic, 20-25ºC, although performed in darkness or diffuse light). The duration for the test to be conducted was up to 28 days. The primary measuring parameter of biodegradation will be based on the removal of Dissolved Organic Carbon (DOC), but Chemical Oxygen Demand (COD) might also be applicable. The OECD 302B test is generally for substances that are not readily biodegradable, are insoluble, or the OECD 301 criteria are not applicable.

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    Introduction of OECD 302 B

    The OECD 302 B test, or Zahn-Wellens test, assesses the inherent biodegradability of organic compounds under optimal aerobic conditions. It is not a ready biodegradability test (in the OECD 301 series), which is a measure of rapid decomposition, but rather a measure of whether or not a substance will biodegrade, given enough time and acclimation. It is typically used in regulatory assessments of chemicals that are unlikely to pass the ready biodegradability criteria, but do not pose a meaningful persistence risk.

    Test Method of OECD 302B

    Test procedure This test evaluates the amount of dissolved organic carbon (DOC) removed or the chemical oxygen demand (COD). The percentage of degradation is calculated from the ratio of DOC removed or COD removed to the original DOC applied, or the initial COD introduced.

    OECD 302B Sample Preparation

    Specimen DetailsA mixture is created that includes the test substance, mineral nutrients, and a considerable quantity of activated sludge. 
    Incubation ConditionThis mixture is stirred and aerated at a temperature range of 20–25°C, either in the absence of light or under indirect lighting, for a period of up to 28 days. 

    OECD 302B Results and Interpretation

    The concentration of DOC or COD is evaluated periodically to determine the extent of biodegradation. The test is considered valid if the reference compound shows a removal rate of at least 70% within 14 days, and the DOC or COD in the test suspension declines steadily over time, signifying biodegradation.

    Service NameRemarks
    OECD 302B
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    Materials Commonly Tested with OECD 302B

    Commonly used for testing chemicals like surfactants, personal care products, and industrial compounds.

    OECD 302 B Related Articles

    OECD 105 determines the solubility of water.

    FAQ's

    Where can I get the oecd 302b tested?

    You can share your oecd 302b testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific oecd 302b test to various testing techniques.

    How much do I need to pay for the oecd 302b test?

    Please contact us for a detailed quote for your oecd 302b testing needs. Cost incurred to carry out different oecd 302b testing methodology depends on the type of raw material; number of samples, coupons, or specimens; test conditions, turn around time etc. Costs of some ASTM testing methods start from $100 and the final value depends upon the factors listed above. Please contact us for the best and latest prices.

    How many samples are required for oecd 302b?

    The required number of samples or specimens should comply with the procedure given in the oecd 302b standard. However, the MaTestLab operations team can assist you for your special requirements once you share your testing details with us.

    How much discount can I get on the oecd 302b test?

    MaTestLab has a vast testing laboratory network, hence we bring you the best testing facilities in a cost-effective way. We offer considerable discounts (15-20%) to our returning customers based on test volume and frequency.

    How many days will it take to complete the oecd 302b test?

    The turnaround time for oecd 302b test methodology depends upon the test procedure mentioned in the standard test document. However, we at MaTestLab understand your research requirements and hence try to get your test completed within the least possible time.

    Where can I get the oecd 302b tested?

    You can share your oecd 302b testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific oecd 302b test to various testing techniques.

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