The Netherlands drops COD from the wastewater levy and brings in organic carbon
From 1 January 2026 the wastewater discharge levy is based on total organic carbon determined to NEN-EN-ISO 20236:2024, not on chemical oxygen demand. The reason is the potassium dichromate, mercury and hexavalent chromium used in the old method.
- The amendment to the water regulation replaces chemical oxygen demand with total organic carbon in the oxygen consumption formula, and Kjeldahl nitrogen with total bound nitrogen less nitrites and nitrates.
- A reference to NEN-EN-ISO 20236:2024 was added to the table of analytical requirements; references to standards became static, that is with the year of issue and the language version stated.
- The statutory conversion is COD equal to three times organic carbon; where the ratio falls between 2.5 and 3.5 the value three applies, and below 2.5 a plant may demonstrate its own ratio by running both methods.
- The draft was notified to the European Commission on 22 July 2025 (number 2025/0395/NL) and the standstill ended on 23 October 2025 with no comments; organic carbon costs slightly more per determination than COD, but disposal of COD reagents is getting dearer.
Source: Staatscourant 2025 nr 37639 — zmiana rozporządzenia wodnego (Waterregeling)