Zahn-Wellens/EMPA Test (OECD 302B)
Freshwater Modified Zahn-Wellens/EMPA Test
This freshwater method is not suitable for volatile materials.
The test material is added to a large volume of activated sludge and nutrient mixture, and the decline in dissolved oxygen concentration measured frequently. The duration of the study is generally 28 days but may be extended if a significant lag period is noted at the start. A result of > 70% degradation means that the substance is ‘ultimately’ biodegradable but < 70% and > 20%, it is ‘inherently’ biodegradable.