defr Glossar


Abbreviation for “Formazine Nephelometric Unit”. Calibration unit in compliance with standard ISO 7027 for turbidity measurement using the scattered light method. Based on a formazine solution. Calibration (turbidity)

Typical turbidity values for water FNU
Limit in Central Europe 1
Targeted by most waterworks 0.1
Guideline WTO (ideal) < 5 (< 1)
Raw water* < 0.5
After flocculation and filtration* < 0.2

Subject to the source of Raw water its turbidity can and does very greatly, for instance river water extracted for use in a water treatment plant can easily reach 200FNU and greater.



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