Interpretation of Class 1A TN Limit in GB 18918 Discharge Standard

The 'Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants' GB 18918-2002 Class 1A sets total nitrogen (as N) ≤15mg/L; some sensitive waters apply stricter local standards (e.g. quasi-Class IV TN ≤10mg/L).

To meet the limit, WWTPs with insufficient carbon commonly add sodium acetate and other carbon sources. Understanding the limit is the premise for carbon source selection and dosage design; HG/T 5959-2021 provides basis for carbon source products.