Ammonia Nitrogen Discharge Standards for Industrial Wastewater

Ammonia nitrogen is one of the key pollutants regulated in industrial wastewater discharges in China. Excessive ammonia nitrogen released into water bodies can trigger eutrophication, deplete dissolved oxygen, and exert direct toxicity on aquatic life. 

To address these risks, China has established a multi‑tiered regulatory framework that sets ammonia nitrogen limits according to the discharge pathway, the industry sector, and the receiving environment.

The General Standard

The Integrated Wastewater Discharge Standard (GB 8978‑1996) serves as the foundational regulation for most industrial facilities. Under this standard, ammonia nitrogen limits are classified into three tiers based on the discharge destination:

Tier I applies to direct discharge into sensitive surface waters. For most industrial sectors, the limit is 15 mg/L, though certain industries such as pharmaceutical raw materials, dyes, and petrochemicals face a Tier I limit of 15 mg/L as well.

Tier II applies to direct discharge into less sensitive water bodies. The limit is generally 25 mg/L for most facilities, but for petroleum, pharmaceutical, and dye industries it is set at 50 mg/L.

Tier III applies to wastewater discharged into municipal sewer systems that feed into secondary treatment plants. The limit is typically not specified in the standard itself, as the focus is on ensuring compatibility with downstream treatment.

Indirect Discharge and Sewer Connection Standards

When industrial wastewater is pretreated and discharged into municipal sewer networks, it must comply with the Wastewater Quality Standard for Discharge into Municipal Sewers (GB/T 31962‑2015). This standard sets the ammonia nitrogen limit at 45 mg/L for the B‑level control requirement. Facilities that discharge into municipal sewers often need to meet both the general Tier III requirements of GB 8978‑1996 and the specific limits of GB/T 31962‑2015.

Sector‑Specific Standards

For key industrial sectors, dedicated effluent standards impose stricter ammonia nitrogen limits than the general standard:

Textile dyeing and finishing (GB 4287‑2012): The indirect discharge limit for ammonia nitrogen is 20 mg/L.

Petroleum refining (GB 31570‑2015): The indirect discharge limit is set at 8.0 mg/L.

Synthetic ammonia industry (GB 13458‑2013): The indirect discharge limit is 50 mg/L, with direct discharge limited to 25 mg/L.

Local Standards and Special Protection Areas

Provincial and municipal authorities may impose more stringent limits based on local environmental conditions. In ecologically sensitive regions such as the Taihu Lake basin, ammonia nitrogen limits are significantly tighter. For example, Jiangsu Province's Taihu Lake Region Discharge Standard (DB32/1072‑2018) sets ammonia nitrogen limits as low as 4–5 mg/L for certain facilities. 

In Zhejiang Province, the Indirect Discharge Limits for Nitrogen and Phosphorus Pollutants from Industrial Enterprises (DB33/887‑2013) establishes an ammonia nitrogen limit of 35 mg/L for indirect discharges.