ISO 11348-3:2007

Overview

ISO 11348-3:2007 specifies a standardized luminescent bacteria test using freeze‑dried Vibrio fischeri (NRRL B‑11177) to assess the inhibitory effect of water samples on bacterial light emission. It is one part of the ISO 11348 series for measuring toxicity by luminescence inhibition. The method applies to wastewater, surface and groundwater, sea and brackish water, sediment eluates, pore water, leachates, and single substances diluted in water.

Key topics and technical requirements

• Test organism & reagents: Uses commercially available freeze‑dried Vibrio fischeri reconstituted with a specified salt solution (20 g/L NaCl; 2.035 g/L MgCl2·6H2O; 0.30 g/L KCl). Store freeze‑dried bacteria at −18 °C to −20 °C.
• Diluent & reference substances: Sodium chloride diluent (20 g/L NaCl). Reference reagents include zinc sulfate, 3,5‑dichlorophenol and potassium dichromate prepared as stock solutions for quality control.
• Apparatus & conditions: Luminometer with thermostatted measuring cell (15 °C ±1 °C), thermo‑block, pH meter, oxygen probe (ISO 5814), accurate pipettes and freezer/incubator.
• Sample preparation: Measure oxygen (>3 mg/L required), adjust pH when necessary (acceptable test range pH 6.0–8.5), manage salinity (add NaCl to 20 g/L where appropriate; avoid hyperosmotic test conditions above ~35 g/L NaCl equivalent), reduce turbidity by settling/centrifugation/filtration.
• Procedure & evaluation: Batch test combining sample (or dilution series) with bacterial suspension; luminescence measured after defined contact times (5, 15 or 30 min). Results expressed as percent inhibition, LID (see Annex B) and/or EC values (e.g., EC20, EC50) derived from dilution series.
• Interferences & validity: Colour, turbidity, oxygen demand, pH extremes, and high salinity can bias results; the standard includes correction methods (Annex A) and validity/precision criteria (Annex C).

Applications and users

ISO 11348-3 is used for rapid toxicity screening and comparative biotesting in:

• Environmental and public health laboratories
• Wastewater and industrial effluent monitoring
• Regulatory compliance and permitting programs
• Research on aquatic toxicity, sediment eluates and leachate impact
• Contract environmental testing and consulting

This method helps detect toxic effects from metals, organics and complex mixtures and provides quantifiable endpoints (EC values) for risk assessment and treatment evaluation.

Related standards

• ISO 11348-1: fresh bacterial cultures method
• ISO 11348-2: liquid‑dried bacteria method
• ISO 5667-16: sampling guidance for biotesting
• ISO 5814: dissolved oxygen measurement

Keywords: ISO 11348-3, luminescent bacteria test, Vibrio fischeri, freeze-dried bacteria, water quality testing, toxicity testing, EC50, biotesting.