Compared to traditional water treatment processes, magnetic separation technology is an emerging purification technique. Its application in wastewater treatment primarily involves three methods: direct magnetic separation, indirect magnetic separation, and microbial magnetic separation.

Magnetic separation for wastewater treatment mainly utilizes the coagulability of pollutants and the enhancement of their magnetic properties. Coagulation refers to the process where pollutants containing ferromagnetic or paramagnetic properties form larger particles under the influence of a magnetic field and are subsequently removed. The magnetic properties of weakly paramagnetic or non-magnetic pollutants are enhanced by adding external magnetic seeds, enabling their removal through magnetic separation. Additionally, external microorganisms are used to adsorb paramagnetic ions in wastewater, allowing for the removal of ionic paramagnetic pollutants via magnetic separation.

In recent years, magnetic separation technology has been widely applied and promoted in many river and lake water restoration projects across the country due to its advantages, such as high water treatment capacity, compact equipment footprint, stable operation, and significant effectiveness in eliminating black and odorous water.

From the validation of technical principles and the design of production processes to the analysis of experimental data and the manufacturing of complete sets of magnetic separation equipment, this technology involves multidisciplinary research in magnetism, fluid dynamics, material anti-corrosion science, organic chemistry, biochemistry, and more. It requires solving numerous technical challenges, such as magnetic flocculation, adsorption and removal, slag and sludge discharge, magnetic seed recovery, sludge expulsion, and automatic control. The technology is knowledge-intensive and highly scientific.

Magnetic separation technology primarily includes five aspects: chemical dosing, magnetic flocculation reaction, magnetic separation, magnetic seed recovery and recycling, and sludge treatment. To further improve the efficiency of magnetic separation and stabilize the quality of the treated water, recent research has focused on optimizing the internal hydraulic flow patterns of magnetic separation devices and developing automatic dosing control systems based on effluent quality and separation performance.

Additionally, while magnetic separation technology demonstrates effective removal of suspended solids (SS), biochemical oxygen demand (BOD), and total phosphorus (TP), further research breakthroughs are needed for the efficient removal of ammonia nitrogen (NH3-N) and advanced removal of COD. Developing high-capacity, rapid-reaction, stable-performance physicochemical processes integrated with magnetic separation technology can significantly enhance the removal rates of ammonia nitrogen, COD, SS, and other pollutants, further improving effluent quality and river water environment. This is also a key issue in comprehensively advancing water environment management.