Membrane contact processes

These concentration differences can lead to a difference in osmotic pressure as in Forward Osmosis or a difference in vapor pressure as in Ammonia Membrane Stripping or Membrane Distillation. These new ways of membrane filtration opens new possibillities of selective concentration of fluids. 

Forward Osmosis Process

• The feed is concentrated
• Dilution of the draw solution
• Draw solution needs to be recovered
• Permeate is produced

Examples of draw solution recovery technologies

• Reverse Osmosis: BWRO (0 – 30 g TDS/L)
• Reverse Osmosis: SWRO (30 – 70 g TDS/L)
• High Brine Reverse Osmosis: HBRO (70 – 140 g TDS/L)
• Membrane Distillation: MD (140 – 250 g TDS/L)

Ammonia recovery from centrate

• Selective removal of ammonium
• Produces liquid fertilizer
• No greenhouse gas emissions (N2O)
• Less use of primary energy than biological processes like Anammox

Membrane distillation

• Hydrophobic membranes for water vapour transport

• Driving for based on difference in vapour pressure

• Compact and scalable

• Use of low grade thermal heat of 60 to 80 C