Overview
ISO 10707:1994 specifies a laboratory method - the closed bottle biochemical oxygen demand (BOD) test - for evaluating the “ultimate” aerobic biodegradability of organic compounds in an aqueous medium. The method measures oxygen uptake by aerobic microorganisms over a standard incubation period (up to 28 days) and expresses biodegradation as a percentage of the compound’s theoretical oxygen demand (ThOD) or, where ThOD is not available, as a percentage of chemical oxygen demand (COD).
Key topics and requirements
- Test principle: Inoculated, air‑saturated mineral medium containing the test compound is incubated in sealed bottles; biodegradation is followed by measuring dissolved oxygen depletion.
- Incubation conditions: Dark, constant temperature (20–25 °C ±1 °C); typical sampling at 0, 7, 14, 21 and 28 days.
- Test concentration and vessels: Test concentration normally ~2 mg/L (higher for poorly biodegradable substances); BOD bottles ~250–300 mL; preparation and filling from larger 2–5 L bottles to avoid aeration.
- Reagents and medium: Standard mineral medium (phosphate buffers, MgSO4, CaCl2, FeCl3, NH4Cl) and aeration to ~9 mg/L dissolved oxygen at 20 °C.
- Inoculum: Secondary effluent (domestic sewage or similar) without sludge flocs; inoculum volume adjusted to provide active cells (typically 10^3–10^6 cells/mL). Preconditioning or pre‑exposure may be used where appropriate.
- Controls and warnings: Include blanks (inoculum only), reference compound controls (e.g., sodium acetate), and inhibition controls where toxicity is suspected. Safety warning: activated sludge and sewage may contain pathogenic organisms; handle with appropriate precautions.
- Calculations: Specific BOD (mg O2 per mg test compound) is corrected by blank inoculum consumption and then expressed as % ThOD (or % COD). Corrections for nitrification (nitrite/nitrate formation) are applied if nitrogenous compounds are tested.
- Output: Biodegradation curve (percentage vs. time) with derived parameters such as lag time, degradation rate and maximum biodegradation.
Applications and users
ISO 10707 is used to:
- Screen chemicals for ultimate aerobic biodegradability in environmental risk assessments.
- Support regulatory submissions, product stewardship and eco‑toxicity evaluations.
- Compare relative biodegradability of formulations, intermediates and new organic substances.
Typical users:
- Environmental chemists and laboratories performing biodegradability testing
- Regulatory and compliance professionals assessing persistence
- Chemical manufacturers, formulators and wastewater treatment researchers
Related standards
Standards referenced for complementary methods and analyses include ISO 9887, ISO 9888 (other biodegradability tests), ISO 10304‑2 (anions analysis), and ISO 5814/ISO 5813 (dissolved oxygen determination/Winkler method).
Open preview (PDF)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)