ISO 10708:1997

Overview - ISO 10708:1997 (Water quality, BOD two‑phase closed bottle test)

ISO 10708:1997 specifies a standardized laboratory method to evaluate the ultimate aerobic biodegradability of organic compounds-particularly poorly water‑soluble substances-by measuring biochemical oxygen demand (BOD) in a two‑phase closed bottle test. The method follows oxygen uptake by aerobic microorganisms in an aqueous medium (test compound as sole carbon source) over up to 28 days and expresses biodegradability as oxygen uptake relative to the theoretical oxygen demand (ThOD) or chemical oxygen demand (COD).

Safety: activated sludge/sewage may contain pathogenic organisms; handle inocula and unknown/toxic compounds with appropriate precautions.

Key topics and technical requirements

• Scope and applicability

  • For water‑soluble or poorly soluble organic compounds that do not adsorb on the oxygen electrode or inhibit test microorganisms at the chosen concentration.
  • Final test concentration typically about 100 mg/L ThOD (annex A for ThOD calculation; COD alternative in annex B).

• Test principle

  • Closed bottles containing liquid and headspace air are stirred/shaken to ensure steady oxygen partitioning between gas and liquid phases.
  • Dissolved oxygen is measured regularly; total oxygen uptake is computed from differences between blanks and test bottles and expressed as % biodegradation (BOD/ThOD or BOD/COD).

• Environmental and incubation conditions

  • Temperature: 20–25 °C with ±0.5 °C control.
  • Incubation in the dark or diffused light; test duration up to 28 days.

• Apparatus and reagents

  • Gas‑tight incubation bottles (200–300 mL), inert stoppers, magnetic stirrers.
  • Oxygen electrode with 0–10 mg/L range and ~1% precision; pH meter; optional DOC analyser.
  • Standard test medium (solutions A–D) and guidance on preparing poorly water‑soluble test compounds (see ISO 10634).

• Inoculum

  • From secondary effluent, activated sludge or other sources; stabilized and standardized to meet microbial activity and suspended solids requirements.

• Validation and corrections

  • Annexes include ThOD calculation (A), COD determination (B), nitrification correction (C), and example degradation curves (D).

Practical applications and users

• Environmental laboratories performing biodegradability screening of industrial chemicals, pesticides, pharmaceuticals, specialty chemicals.
• Regulatory testing and environmental risk assessment where demonstrating ultimate biodegradation or establishing BOD/COD relationships is required.
• Chemical manufacturers, contract testing labs, water quality consultancies, and regulators who need standardized, comparable aerobic biodegradability data for poorly soluble compounds.

Related standards

• ISO 10634:1995 - Preparation/treatment of poorly water‑soluble compounds for biodegradability tests
• ISO 9408, ISO 9439 - Alternative respirometric and CO2‑evolution tests (referenced)
• ISO 8192 - Methods for assessing inhibitory effects on bacteria
• ISO 11923 - Determination of suspended solids

Keywords: ISO 10708, biodegradability, biochemical oxygen demand, BOD, two‑phase closed bottle test, ThOD, COD, water quality, poorly water‑soluble compounds, aerobic biodegradation.