As of my last knowledge update in September 2021, the Total Organic Carbon (TOC) standard for surface water in Germany was regulated by the Technical Instructions on Water Quality Monitoring (Technische Anleitung zur Reinhaltung der Gewässer or LAWA). However, specific TOC limits may vary depending on the type and location of the water body.
To get the most up-to-date and precise information on TOC standards for surface water in Germany, I recommend referring to the latest official regulations provided by the relevant authorities or environmental agencies, such as the Federal Environment Agency (Umweltbundesamt) or the respective state-level environmental agencies in Germany. These agencies regularly update and adjust water quality standards and regulations to address changing environmental conditions and requirements.