EN ISO 9888:1999 PDF

Overview

EN ISO 9888:1999 - "Water quality - Evaluation of ultimate aerobic biodegradability of organic compounds in aqueous medium - Static test (Zahn‑Wellens method)" - defines a standardized laboratory procedure to assess how readily organic compounds (or dissolved fractions of wastewater) are mineralized by aerobic microorganisms. The method uses a static aqueous test system with activated sludge as inoculum and quantifies biodegradation primarily by measuring dissolved organic carbon (DOC) or chemical oxygen demand (COD) over a standard test period (normally 28 days).

Key topics and technical requirements

• Test principle: Static (non-continuous) incubation of test compound in inorganic medium with activated sludge; DOC or COD measured initially, after 3 hours (to allow for adsorption), at intermediate times and at the end of the test.
• Target endpoints:
  • Ultimate aerobic biodegradation (mineralization to CO2, water and salts)
  • Primary biodegradation (structural transformation) and total elimination from water as additional information
• Concentration ranges: Select test concentrations to give initial DOC between 50–400 mg/L or COD between 100–1000 mg/L, depending on solubility and toxicity.
• Test conditions:
  • Temperature 20–25 °C, variation ≤ 2 °C
  • Incubation in the dark or diffuse light
  • Aeration and mixing to maintain dissolved oxygen
• Applicability constraints:
  • Test compound should be water‑soluble at test concentration
  • Nonvolatile (negligible vapour pressure) and not prone to foaming
  • Non‑inhibitory to test microorganisms at the chosen concentration (inhibitory effects may require concentration reduction or pre‑exposed inoculum)
• Quality controls:
  • Adsorption assessment at 3 h
  • Abiotic elimination control (without inoculum)
  • Use of reference biodegradable compounds
• Analytical methods: DOC analysis (ISO 8245) or COD (ISO 6060); substance‑specific analyses may supplement interpretation.

Applications and users

EN ISO 9888:1999 is used where a reproducible laboratory measure of aerobic biodegradability is required, including:

• Environmental and research laboratories assessing biodegradation potential of chemicals or wastewater fractions
• Wastewater utilities and process engineers evaluating elimination from aqueous phases
• Chemical manufacturers and environmental consultants conducting biodegradation testing for product development, environmental risk assessment, or monitoring studies

Related standards

• ISO 8245 - Determination of TOC/DOC
• ISO 6060 - Determination of COD
• ISO 8192 - Methods to assess inhibition/toxicity
• ISO 11733 and ISO 15462 - Simulation tests and guidance for predicting behaviour in full‑scale treatment systems

Keywords: EN ISO 9888:1999, Zahn‑Wellens method, aerobic biodegradability, DOC, COD, static test, activated sludge, water quality standard.