ISO 9408: Ultimate Biodegradability Test - Oxygen Consumption (ISO/IEC 17025:2017 Accredited)

ISO 9408 is an aqueous aerobic biodegradability test that determines the ultimate aerobic biodegradability of organic compounds in aqueous medium by measuring oxygen demand during biodegradation in a closed respirometer. The test normally lasts for 28 days.

CONCEPT AND PRINCIPLE

Similar to the OECD 301F Ready Biodegradability Test, ISO 9408 determines the biodegradability of a material by measuring oxygen consumption during the biodegradation process in a period of 28 days in a closed bottle setup (with head space). The degradation percentage is calculated as the ratio of oxygen consumption to the theoretical oxygen demand (ThOD).

The oxygen consumption is usually determined by measuring the quantity of oxygen (produced electrolytically) required to compensate the consumed one to maintain a constant gas volume/pressure in the respirometer flask, or from the change in the volume or pressure in the flask without compensating the consumed oxygen. The evolved CO₂ is absorbed by sodium hydroxide solution present in a tube in the flask.

The formula of the test substance and its purity may be known to calculate the ThOD. If the ThOD cannot be obtained, the chemical oxygen demand (COD) may be experimentally determined and used as a less satisfactory alternative.

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.

This method is capable of testing samples that are highly soluble, poorly soluble, insoluble, volatile, involatile, and/or adsorbing.