In Situ Treatment and Underground Reuse Using PolyCera Hydro Ultrafiltration Membrane
Application Overview
Coal mines generate water containing coal fines, rock particles, suspended solids, oil, and microorganisms. Conventional produced water treatment systems are commonly installed above ground, requiring mine water to be pumped to the surface before treatment and, where needed, returned underground for reuse.
At the Xuzhuang Coal Mine in Jiangsu, China, this approach created high energy demand, extensive piping, and unnecessary treatment complexity.
In 2025 a 360 m³/h underground treatment system for coal mine water reclamation was commisioned using PolyCera Hydro ultrafiltration membranes. The objective was to treat mine water close to its source, produce reclaimed water for direct underground reuse, and reduce the energy required for water lifting and redistribution.
Project Background
The mine previously relied on an above ground treatment process using coagulation, sedimentation, filtration, and disinfection. Although the system met basic water quality requirements, it required all mine water to be lifted to the surface and treated water to be pumped back underground.
The process also depended on PAC and PAM dosing, multiple treatment stages, extensive piping, and significant operator input. Rising water quality requirements and the demand for higher quality reclaimed water increased the need for a simpler and more efficient approach.
The new system relocates treatment underground and replaces several conventional process stages with compact PolyCera membrane filtration.
Process Design for Produced Water Treatment
The system combines underground sedimentation, pre filtration, and PolyCera Hydro ultrafiltration to produce water suitable for direct reuse.
1. Primary Sedimentation
Mine water enters an underground sedimentation sump, where existing tunnels and mine spaces provide equalization and settling of larger coal and mineral particles.
2. Pre Filtration
Pre filtration removes larger debris such as coal chips, rock particles, and sand before the membrane stage.
3. Produced Water Treatment using PolyCera Hydro Ultrafiltration
The water passes through a skid mounted PolyCera Hydro UF system, which removes suspended solids, fine coal particles, oil, colloids, and microorganisms.
The hydrophilic and backwashable membrane supports stable operation under variable mine water conditions while reducing the need for coagulation, clarification, and conventional filtration stages. PolyCera Hydro is positioned for industrial water applications requiring high fouling resistance and reliable solids removal.
4. Underground Reuse
Treated water is stored in a clean water sump and reused underground for dust suppression, equipment cooling, hydraulic support systems, fire protection, and other mine operations.
Excess treated water can be pumped to the surface for further production or utility use.
5. Residual Water Recirculation
Backwash and concentrate are returned to underground sumps or goaf areas for settling and recirculation into the treatment cycle.
Results of Produced Water Treatment Project
The system produced reclaimed water with suspended solids below 1 mg/L, turbidity below 1 NTU, and a median particle size below 1 μm. The treated water exceeded the technical requirements of GB50383 2016 for coal mine fire protection and spraying systems.
By treating water underground, the project reduced the need to lift untreated water to the surface and return reclaimed water to the mine. Treatment costs were reported at below USD 0.37 per m³. The compact and automated system also reduced chemical use, equipment requirements, operator input, and land demand.
The project demonstrated that deep mine water can be treated close to its source using a short process membrane system, while producing water suitable for direct underground reuse.
Conclusion
The Xuzhuang project demonstrates how underground treatment can simplify coal mine water reclamation. By combining local sedimentation, pre filtration, and PolyCera® Hydro ultrafiltration, the system produces high quality reclaimed water directly underground while reducing pumping demand, chemical use, process complexity, and operating cost.
The project provides a replicable model for deep mines seeking to improve water reuse and reduce the infrastructure required for conventional above ground treatment.