According to the 2018 edition of the Shanghai Municipal Local Standard for Integrated Wastewater Discharge (DB31/199-2018), the wastewater discharge outlet of a power generation plant operated by Baosteel Co., Ltd. is located in a sensitive water area. Consequently, the ammonia nitrogen discharge limit has been reduced from 10 mg/L to 1.5 mg/L, and the organic matter discharge limit has been lowered from 100 mg/L to 50 mg/L.

In the accident water pool area: There are two accident water pools in this area. New online automatic monitoring systems for ammonia nitrogen have been installed to enable continuous monitoring of ammonia nitrogen levels in the accident water pools. Additionally, a new sodium hypochlorite dosing pump has been installed, which is connected to the existing sodium hypochlorite storage tanks and interlocked with the ammonia nitrogen monitoring system. This configuration enables automatic and precise dosing control for both accident water pools.

In the drainage treatment system of Phase I of the chemical water treatment station: Online automatic monitoring systems for ammonia nitrogen have been installed at the clarification tank, B1 waste water tank, B3 waste water tank, B4 waste water tank, and B5 tank. These monitoring systems are interlocked with the sodium hypochlorite dosing pump to enable automated dosing control throughout the drainage treatment process.

Equipment Used：

NHNG-3010 Online Automatic Ammonia Nitrogen Monitor

YCL-3100 Intelligent pretreatment system for water quality sampling

To comply with the updated discharge standards, Baosteel Co., Ltd.'s power generation plant has installed ammonia nitrogen extraction and pretreatment equipment at the wastewater discharge outlet. The existing wastewater treatment system has undergone optimization and renovation to ensure that both ammonia nitrogen and organic matter are effectively treated to meet the new discharge requirements. These improvements guarantee timely and efficient wastewater treatment and significantly reduce the environmental risks associated with excessive wastewater discharge.

Why is it necessary to monitor ammonia nitrogen levels at the drainage outlets of steel mills?

Measuring ammonia nitrogen (NH₃-N) at steel mill outfalls is critical for both environmental protection and compliance with regulations, as steel production processes inherently generate ammonia-containing wastewater that poses significant risks if improperly discharged.

Firstly, ammonia nitrogen is highly toxic to aquatic organisms. Even at low concentrations, it can damage the gills of fish and other aquatic life, disrupt their metabolic functions, and lead to mass mortality. Moreover, excess ammonia in water bodies triggers eutrophication—a process where ammonia is converted into nitrates by bacteria, fueling the overgrowth of algae. This algal bloom depletes dissolved oxygen in water, creating "dead zones" where most aquatic organisms cannot survive, severely破坏ing aquatic ecosystems.

Secondly, steel mills are legally bound by national and local environmental standards (e.g., China’s Integrated Wastewater Discharge Standard, the EU’s Industrial Emissions Directive). These standards set strict limits on ammonia nitrogen concentrations in discharged wastewater. Regular monitoring ensures mills meet these limits, avoiding fines, operational suspensions, or legal liabilities resulting from non-compliance.

Additionally, ammonia nitrogen measurements serve as a key indicator of the efficiency of the mill’s wastewater treatment system. If ammonia levels exceed the standard, it signals potential issues in the treatment process (e.g., malfunctioning of biological treatment units), allowing engineers to identify and rectify problems promptly—preventing untreated or poorly treated wastewater from entering the environment.

In summary, monitoring ammonia nitrogen at steel mill outfalls is a fundamental practice to mitigate ecological harm, adhere to legal requirements, and maintain the reliability of wastewater treatment processes.