1. Initial Conditions – Remediation of extensive contamination from uranium mining
Between 1966 and 1996, a total of 15,000 boreholes were injected with:
• 4,100,000 tons of sulfuric acid (H₂SO₄)
• 320,000 tons of nitric acid (HNO₃)
• 111,000 tons of ammonium ions (NH₄⁺)
• 16,000 tons of hydrofluoric acid (HF)
The total volume of contaminated groundwater exceeded 370 million m³. As part of the remediation process, residual process solutions (RPS) were extracted, subjected to evaporation and alum crystallization, and then neutralized using lime milk. The resulting neutralization sludge had to be reliably filtered and dewatered at high throughput.
2. Technological Solution Provided by ENVITES
Between 2008 and 2009, ENVITES implemented a complete technological solution for mechanical sludge dewatering in an operation with a nominal capacity of 132 m³/h and sludge production of up to 46 t/h. The delivered solution included:
• 8× chamber filter press ENVITES K1500/100
◦ Filtration volume: 6,470 dm³ each
◦ Filter cloth washing system
• Feeding pumps for the filter presses
◦ Centrifugal pumps for pre-filling
◦ High-pressure membrane pumps
• Redler conveyor system for transporting dewatered filter cake
◦ 8× longitudinal + 1× transverse redler
• 2× suspension storage tanks (each 150 m³, stainless steel construction)
• Storage tanks for distillate, filtrate, and HCl
• Mine water pumps for cake washing
• HCl pumps for cloth regeneration
• Compressor station for pneumatic system operation
3. Results and Benefits of the Solution
• High dewatering efficiency – filter cake dry matter content: 48–52 %
• Reliable and continuous operation under high process load
• Automated control with minimal operator requirements
• Corrosion-resistant materials suitable for aggressive media
• Optimized handling of by-products (filtrate, distillate, acids)
• Efficient logistics of filter cake transport via conveyor system
Summary
The groundwater remediation project following uranium in-situ leaching ranks among the largest environmental remediation efforts in the Czech Republic. ENVITES designed and delivered a robust solution for neutralization sludge filtration, enabling reliable dewatering under demanding operating conditions. The use of K1500/100 filter presses combined with a sophisticated pumping and transport system ensured not only the required efficiency but also high operational reliability and chemical resistance. The solution significantly contributed to the overall progress of remediation in the affected area.
