1. Introduction  

To contextualize the discussion of steel plant wastewater, it is first necessary to clarify the definition of steel. As a ferrous metal, steel encompasses three primary forms: pig iron, wrought iron, and steel itself. This paper addresses two core questions: How is wastewater generated in steel plants? And what measures are required for wastewater treatment and monitoring? The analysis is conducted in collaboration with manufacturers of online water quality monitoring instruments.

2. Characteristics and Classification of Steel Plant Wastewater  

The source and properties of steel plant wastewater vary with production processes, such as wastewater from steelmaking workshops and ironmaking workshops. From a functional perspective, it can be categorized into two main types: washing wastewater and indirect cooling wastewater. To ensure compliant discharge, wastewater must first undergo disinfection, followed by post-disinfection monitoring. Discharge is only permitted if all (indicators) meet regulatory standards.

3. Key Monitoring Indicators  

3.1 Total Wastewater Discharge Outlets  

Monitoring parameters include: flow rate, pH value, suspended solids (SS), chemical oxygen demand (COD), ammonia nitrogen (NH₃-N), total nitrogen (TN), total phosphorus (TP), total iron (TFe), total zinc (TZn), volatile phenols, fluoride (F⁻), cyanide (CN⁻), petroleum hydrocarbons, and total copper (TCu).

3.2 Workshop or Production Facility Discharge Outlets  

Key parameters to monitor are flow rate and heavy metal indicators, such as total arsenic (TAs), total chromium (TCr), total lead (TPb), total nickel (TNi), total cadmium (TCd), and total mercury (THg).

4. Supplementary Monitoring Requirements  

• Automatic Monitoring Equipment Installation:Local environmental protection authorities shall explicitly mandate the installation of automatic water quality monitoring systems to enable real-time tracking of all key indicators.
• Rainwater Discharge Outlets: Rainwater discharge outlets require regular attention. Where conditions allow, daily monitoring should be conducted for indicators including petroleum hydrocarbons and COD.
• Domestic Sewage Discharge: Domestic sewage discharged directly into the environment must be monitored daily, focusing on conventional parameters such as COD, NH₃-N, TN, and TP.

5. Conclusion  

Strict adherence to relevant regulatory requirements is imperative to ensure that wastewater discharged from steel plants meets all compliance standards.