Overview
ISO/TR 15462:2006 - "Water quality - Selection of tests for biodegradability" is a Technical Report from ISO/TC 147 that provides an authoritative overview and practical recommendations for choosing standardized biodegradation tests for the aquatic environment. The document summarizes ISO methods used to determine the biodegradability of chemical substances and wastewaters under standardized conditions, and it includes guidance on using inhibitory (toxicity) tests with bacteria or mixed inocula to inform test selection and interpretation.
Key topics and requirements
- Purpose and scope: Guidance for selecting appropriate biodegradation tests to predict behaviour in rivers, lakes, marine waters, wastewater treatment plants and anaerobic digesters.
- Test types covered: Aerobic and anaerobic methods, including DOC removal, CO2 evolution, oxygen consumption, closed-bottle BOD tests, activated-sludge simulation and shake-flask/river simulation tests.
- Representative ISO methods: ISO 7827 (DOC removal), ISO 9439 (CO2 evolution), ISO 9408 (oxygen consumption), ISO 10707/10708 (closed-bottle/BOD tests), ISO 9887/9888 (high-inoculum tests), ISO 11733 (activated sludge simulation), ISO 11734 (biogas/anaerobic) and ISO 14592 (low-concentration river/lake simulation). ISO 16221 is noted for marine adaptations.
- Analytical parameters: DOC, TOC, BOD, COD, CO2 production, oxygen uptake and substance-specific analyses are highlighted as appropriate endpoints.
- Factors affecting results: The report stresses that biodegradation outcomes depend on inoculum source and density, aerobic vs anaerobic conditions, test concentration, toxicity to inoculum, volatility, adsorption and bioavailability, test duration and analytical sensitivity.
- Practical test settings: Test duration examples include 28 days for many ready biodegradability tests and shorter BOD screening (e.g., 5 days) for wastewater. Activated sludge inocula are commonly used (document references ≤ 30 mg/l dry substance), and anaerobic digesters operate near 35 °C in guidance examples.
- Use of inhibitory/toxicity tests: Determining inoculum toxicity before biodegradation testing is recommended to avoid false negatives and to select appropriate test designs.
Applications and users
Who benefits:
- Environmental testing laboratories performing biodegradability assays
- Chemical manufacturers and formulators assessing environmental fate for registration and compliance
- Regulatory agencies and risk assessors interpreting biodegradability data
- Wastewater treatment operators and process engineers evaluating treatment and sludge impacts
- Environmental consultants and ecotoxicologists choosing suitable test strategies
Practical uses:
- Selecting the most predictive test for a given substance (ready vs inherent biodegradability)
- Designing test conditions (aerobic/anaerobic, inoculum preparation, concentration) to avoid inhibition or analytical limits
- Interpreting variable or conflicting biodegradation results across compartments (freshwater vs marine, aerobic vs anaerobic)
Related standards
- Annex A of ISO/TR 15462 compares ISO methods with OECD biodegradability guidelines - useful for cross-referencing regulatory test requirements and international compliance.
