Hybrid nanofiltration–reverse osmosis for selective nitrate removal

Prof. Michal Green | Civil and Environmental Engineering


Sustainability and Energy

The Technology

The inherent preference of particular nano-filtration membranes for rejecting chloride and sodium over nitrate ions is utilized in a preliminary NF stage to remove Na+, Cl+, Ca2+ and Mg2+ to a side stream. In a second stage, RO is applied to remove NO3- and the RO permeate is mixed with the side stream of the NF stage to create product water low in nitrate, yet with a balanced composition consisting all the required species and minerals.


  • Better balanced product water
  • Production of low salinity brines allowed to be discharged to sewerage systems
  • Less water treated by the RO
  • Significant increase in total recovery ratio
  • Minimization of calcium carbonate precipitation potential on the RO membrane

Applications and Opportunities 

  • Increase in nitrate concentrations is observed in ground waters around the globe, mostly resulting from intensive application of fertilizers. Removing the nitrates from ground water is required and mostly done by reverse osmosis. RO has some drawbacks – the need to re-mineralize the product water and the need to treat the brine before disposing it as well as elongating the membrane life can all be achieved using this invention.
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Oz Mahlebani
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