Sum parameters PFAS 20 and PFAS 4

What lies behind the terms PFAS 20 and PFAS 4?

The terms ‘PFAS 20’ and ‘PFAS 4’ are regulatory sum parameters in the context of the EU Drinking Water Directive (EU 2020/2184) and the German Drinking Water Ordinance. They are used to assess the contamination of water samples with per- and polyfluoroalkyl substances (PFAS) in manageable, analysable groups. PFAS are chemically particularly stable compounds that occur in many industrial processes. Due to their persistence and potential health risks, they need to be monitored more closely.  

PFAS 20 refers to the sum of 20 specifically defined individual PFAS substances with different chain lengths. This sum parameter is used for drinking water monitoring in the EU and will become mandatory in Germany from 12 January 2026 with a limit value of 0.1 µg/L.  

PFAS 4 is a more focused parameter that includes four PFAS substances with particularly high toxicological ratings (PFOS, PFOA, PFHxS and PFNA). A stricter limit value of 0.02 µg/L will apply to this group in Germany from 12 January 2028.  

What significance do these two parameters have for water treatment?

For industrial, medical or municipal applications, there are clear requirements for:

• Analysis and monitoring: Selection of targeted monitoring methods for PFAS-20 and PFAS-4. Treatment concepts: Effective removal using activated carbon, ion exchange or membrane processes.
• Documentation and compliance: Verification in regulated industries and safe operational management.

Herco supports customers with system-specific engineering, validated treatment concepts and documentation-compliant solutions for handling PFAS-contaminated water.

Here you can find our PFAS removal solutions.