Overview
ISO 20227:2017 - Water quality - provides a standardized microbiotest for assessing the growth inhibition effects of waste waters, natural waters and chemicals on the duckweed Spirodela polyrhiza. The method is stock culture independent, using stored turions that are germinated on demand. The assay combines a 3‑day turion germination with a 3‑day toxicity exposure in multiwell plates and uses image analysis of the first frond area (t = 0 h and t = 72 h) to calculate growth inhibition and ECx values.
Keywords: ISO 20227:2017, water quality, Spirodela polyrhiza, duckweed, microbiotest, growth inhibition, wastewater toxicity, pesticides, ecotoxicology.
Key Topics
- Test species & material: Spirodela polyrhiza germinated from stored turions (no continuous stock culturing required).
- Test design: 3 d germination followed by a 3 d exposure in a 6×8 multiwell plate; photographic capture at t = 0 h and t = 72 h.
- Endpoint & analysis: Measurement of first-frond area by image analysis; calculation of growth, growth inhibition and ECx (e.g., EC50) values.
- Test medium: Uses modified Steinberg medium (as in ISO 20079 / OECD guidelines) for germination and exposure; toxicant dilutions prepared in this medium.
- Environmental conditions: Incubation at approximately 25 °C with continuous illumination (minimum ~6 000 lx).
- Applicability: Suitable for treated municipal waste water, industrial effluents, natural waters, pure chemicals, plant protection products and pesticides.
- Quality & validation: Includes procedures for range-finding, definitive tests, reference chemicals, validity criteria and data reporting.
Applications
- Routine ecotoxicity screening of wastewater effluents and receiving waters.
- Regulatory testing of pesticides and plant protection products for aquatic hazard assessment.
- Screening of industrial discharges and site-specific water quality monitoring.
- Laboratory and contract-testing services seeking a compact, rapid assay: the method is space- and resource-efficient, requires minimal equipment, and supports high throughput via multiwell plates.
- Research in aquatic toxicology and risk assessment where a primary-producer endpoint (duckweed growth) is relevant.
Who Would Use This Standard
- Environmental testing laboratories and contract labs
- Regulatory agencies and water quality authorities
- Wastewater treatment operators and environmental consultants
- Agrochemical and chemical manufacturers performing ecotoxicity testing
- Academic researchers in aquatic ecotoxicology
Related Standards
- ISO 20079 (duckweed growth inhibition test / modified Steinberg medium)
- ISO 5667-16 (sampling guidance for biotesting)
- OECD guidelines referenced for duckweed testing and comparative methods
ISO 20227:2017 delivers a practical, reproducible microbiotest for water quality and chemical hazard assessment using Spirodela polyrhiza, combining accessibility (stock culture independence) with standardized data outputs (growth inhibition and ECx).