Abstract: The overflow water from the concentration operation (also known as middling concentra⁃ tion) of magnetic separation tailings before flotation in the concentrator of Longqiao Mining Company Con⁃ centrator runs muddy seriously. In order to solve this problem，on the basis of industrial test demonstra⁃ tion，it is proposed to lead the turbid overflow water to the idle ϕ53 m thickener and flocculant was added to make the overflow water of the ϕ53 m thickener clarified. Meanwhile，the underflow is filtered by pres⁃ sure，realizing the goal of zero discharge of the enterprise's production tailings，creating conditions for the closure of the tailings reservoir in the later stage and ensuring the sustainable development of the enter⁃ prise. The quality of backwater has been greatly improved and the consumption has been significantly in⁃ creased，which has greatly reduced the operation time of the three-stage pump and reduced the annual wa⁃ ter cost by 3 million yuan. The volume utilization rate of the high-level pool has been greatly improved， and the human and financial consumption of desilting has been reduced to zero. The sanitation of the work⁃ ing environment of the concentrator has also been significantly improved.

Key words: magnetic separation first and then flotation, concentration for magnetic separation tailings, overflow water, turbidity, flocculant, backwater