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ISO 16221: Biodegradability Test - Seawater (ISO/IEC 17025:2017 Accredited)

ISO 16221 is an aerobic biodegradation test that determines the ultimate biodegradability of an organic material in seawater relying on the microorganisms originally present in seawater without the addition of a specific inoculum. When artificial seawater is used, however, inoculum may come from other materials of marine origin. Five methods are specified, i.e., (I) DOC die-away, (II) closed bottle, (III) two-phase closed bottle, (IV) CO2 evolution, and (V) CO2 headspace tests. They are directly modified and adapted from the fresh water methods ISO 7827, 10707, 10708, 9439, and 14593, respectively. A maximum test duration of 60 days is allowed.

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CONCEPT

Similar to OECD 306, ISO 16221 targets the aerobic biodegradability of organic materials in marine environment. Directly adapted from five fresh water ISO methods mentioned above, the ISO 16221 provides several different analytical methods and system setups to accommodate materials with a wide range of physico-chemical properties.

Since nutrients (mineral medium) are added and the concentration of test substance is much higher than would be present in the sea, the tests do not simulate the marine environment.

If a sample shows low biodegradability results, it does not necessarily mean it cannot be degraded, but indicates further study is necessary, for example, using as low a concentration of the test compound as possible.

Because the test conditions of marine environments are generally less favorable than those of limnic test systems, the test duration of ISO 16221 can be up to 60 days compared to the usual time of 28 days for fresh water systems.

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OECD 301 CO2 evolution and closed bottle test overview

ISO 16221 Key Summary

The most import fact about ISO 16221 is that it targets marine environment, but is directly based on five ISO methods for fresh water, including ISO 7827, 10707, 10708, 9439, and 14593. The corresponding analytical methods/system setups are (I) DOC die-away, (II) closed bottle, (III) two-phase closed bottle, (IV) CO2 evolution, and (V) CO2 headspace tests. We currently provide analysis for (II), (III) and (IV). Below is a quick review of these five methods:

▶ ISO 7827 - Water quality — Evaluation of the "ready", "ultimate" aerobic biodegradability of organic compounds in an aqueous medium — Method by analysis of dissolved organic carbon (DOC).
▶ ISO 10707 - Water quality — Evaluation in an aqueous medium of the "ultimate" aerobic biodegradability of organic compounds — Method by analysis of biochemical oxygen demand (closed bottle test).
▶ ISO 10708 - Water quality — Evaluation in an aqueous medium of the ultimate aerobic biodegradability of organic compounds — Determination of biochemical oxygen demand in a two-phase closed bottle test.
▶ ISO 9439 - Water quality — Evaluation of ultimate aerobic biodegradability of organic compounds in aqueous medium — Carbon dioxide evolution test.
▶ ISO 14593 - Water quality — Evaluation of ultimate aerobic biodegradability of organic compounds in aqueous medium — Method by analysis of inorganic carbon in sealed vessels (CO2 headspace test).

Information on the toxicity of the test substance is helpful in determining the appropriate dosage so that the material does not inhibit bacteria at the concentration tested.

Depending on the specific method to be selected, this test may handle materials that are insoluble, volatile, and/or adsorbing. 

ISO 16221 Requirement and Applicability

Different testing methods are applicable for materials with different properties. Below is a summary of the applicability of ISO 16221. 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
(I) DOC die-away (based on ISO 7827)DOC
Organic carbon content*---
(II) Closed bottle test (based on ISO 10707)
Dissolved oxygen
ThOD or COD*
+/-++
(III) Two-phase closed bottle test (based on ISO 10708)
Dissolved oxygen
ThOD or COD
+++
(IV) CO2 evolution test (based on ISO 9439)
CO2 evolutionOrganic carbon content+-+
(V) CO2 head space test (based on ISO 14593)
CO2 evolutionOrganic carbon content+++

*"Sample info required" is the information needed to calculate the biodegradation percentages. This must be available for a selected method.
*"Organic carbon content" is the ratio of the organic carbon weight to the weight of the sample. It can be calculated by the sample formula (e.g., acetic acid C2H4O2, carbon content is 12*2/(12*2+1*4+16*2)=40%). Try our Online C% Calculator. If the formula is unknown, we can send the sample out to a third party lab for you for analysis (normally $110 with a 10-day turnaround time).
*"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
.

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