Heavy‑metal‑containing wastewater is generated in numerous industries, including mining, electronics, instrumentation, chemical manufacturing and others. Wastewater discharged during production processes contains heavy metals, which pose hazards to the ecological environment and human health. The water quality and volume of such wastewater are closely related to production processes. Heavy metals in wastewater cannot be decomposed or destroyed. Instead, treatment relies on transferring their existing locations or altering their physical‑chemical forms.

The full process of wastewater treatment is complex, covering treatment technologies and engineering design. Wastewater treatment and Online Water Quality Monitoring are only parts of the whole workflow.

This article, together with Modi, focuses on common heavy‑metal wastewater treatment approaches, as detailed below:

1. Oxidation‑reduction treatment (also known as chemical reduction method). This mature technology has been widely adopted. Its working principle and operation are easy to master, and it can withstand shocks from large‑volume and high‑concentration wastewater. When treating chromium‑containing wastewater with this method, lime used for alkalization will produce large volumes of waste residue. By contrast, sodium hydroxide (NaOH) or sodium carbonate (Na₂CO₃) generate far less sludge.
2. Adsorption method. It removes heavy‑metal ions by utilizing the special structures of adsorbents. Common adsorbents for electroplating heavy‑metal wastewater treatment include activated carbon, sepiolite and glycan resin.
3. Solvent extraction separation method. It is a widely‑used technique for substance separation and purification. As a continuous liquid‑liquid contact operation, it delivers favorable separation performance. Yet highly‑selective extractants are required. Heavy metals in wastewater exist in anionic and cationic forms. Despite its merits, high energy consumption occurs during extractant loss and regeneration, which greatly limits its practical application.
4. Chemical precipitation method. It converts dissolved heavy‑metal substances in wastewater into water‑insoluble heavy‑metal compounds. It falls into two categories: sulfide precipitation and neutralization precipitation.

Currently, heavy‑metal‑bearing wastewater discharged from industrial plants has caused severe impacts on the ecological environment, while wastewater treatment capacity still needs improvement. It is essential for us to jointly protect our home and attach importance to wastewater discharge management. Disinfection and sterilization constitute one part of the treatment process. Water Quality Analyzers can be applied to test various wastewater indicators to verify compliance with discharge standards.