Nanofiltration

Nanofiltration membranes have the advantages of providing a high water flux at low operating pressure and maintaining a high salt and organic matter rejection rate . The nanofiltration process has the benefits of ease of operation, reliability and comparatively low energy consumption  as well as highly efficient pollutant removal. This helps to minimize scale formation on the equipment involved in both reverse osmosis and thermal desalination processes. Recently, nanofiltration membranes have been employed in re-treatment unit operations in both thermal and membrane seawater desalination processes. This has resulted in a reduction in chemicals used in pre-treatment processes as well as a decrease in the energy consumption and water production costs and, therefore, has led to more environmentally friendly processes. To predict nanofiltration membrane erformance, a systematic study on the filtration performance of selected commercial nanofiltration membranes against brackish water and eawater is required. 
 
Benefits Of Water Treatment Nanofiltration 
  • Lower operating costs, 
  • Lower energy costs, 
  • Lower discharge and less wastewater than reverse osmosis, 
  • Reduction of total dissolved solids (TDS) content of slightly brackish water, 
  • Reduction of pesticides and VOCs (organic chemicals), 
  • Reduction of heavy metals, 
  • Reductions of nitrates and sulfates, 
  • Reduction color, tannins, and turbidity, 
  • Being chemical-free (i.e., does not use salts or chemicals), and 
  • Water pH after nanofiltration is typically non aggressive. 
For radionuclide treatment applications, nanofiltration and ultrafiltration have been investigated as an ultra low-level analytical tool to separate actinides from other ionic species in high-level radioactive waste solutions, and as a possible treatment option for waste streams from the Los Alamos National Laboratory Plutonium Treatment Facility (Smith 1993). In these applications, the nanofiltration and ultrafiltration membranes are coupled with water-soluble chelating polymers (WSCP). WSCPs are polymers engineered to contain both highly selective chelating functionalities to bind with targeted metal ions, and solubilizing functionalities to allow the polymer to dissolve in water (Smith et al. 1995). The polymer’s overall size is large enough that it exceeds the rejection limit for an ultrafiltration membrane. When the unchelated polymer is introduced into a solution that contains the target ions for which the chelating groups were designed, the polymer binds with these target ions and nothing else. The chelated polymer can then be separated from the solution (and all other ions in the solution) by ultrafiltration; the chelated target ions can be separated from the polymer by adjusting the solution chemistry; and the regenerated water-soluble chelating polymer can be recycled
 
In these applications, ultrafiltration combined with WSCP has the advantage of being aqueous-based (such as ion exchange resins), has a high throughput and rapid kinetics (like two-phase liquid-liquid extraction systems), but does not have the disadvantage of using organic solvent-based extractants.
 
Applications Of Nano Filtration
  • Partial softening.
  • Water softening
  • Nitrates removal
  • The removal of pesticides from groundwater
  • The removal of heavy metals from wastewater
  • Wastewater recycling in laundries
  • Reduction of organic matter, color, sulphate, chloride, fluoride, bacteria and viral.

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