Forward Osmosis

Forward Osmosis is a gentle process that transports wa­ter across a semi-permeable FO membrane from lower concentration to higher concentration side while effectively retaining any dissolved solutes in the wastewater. The driving force is the osmotic pressure difference between a solution of higher concentra­tion (draw solution) and a solution of lower concentration (feed solution).

Forward Osmosis can be effectively used for the reduction of wastewater volume before the thermal evaporation process as well as for optimizing OPEX

 Applications:

• Pre-concentration of wastewater before evaporation
• A cheaper and more sustainable path towards achieving ZLD
• Pre-concentration of valuable streams before extraction in food as well as product recovery sectors
• Extraction of process water while simultaneously reducing wastewater volume

Advantages:

• Low Operating cost. As the volume of wastewater going to Thermal Evaporators is reduced, the overall CAPEX/OPEX cost of evaporators reduces drastically
• Better rejection of solutes
• Very high tolerance to contaminants (COD/TAN/TDS)

 

Difference between FO and RO

	FO	RO
Operating Pressure	Low (irrespective of TDS)	High (depending on TDS)
Fouling	FO membranes are of low fouling nature and easily recoverable	Organic fouling is a major issue for RO membranes
COD Tolerance	COD < 100,000 ppm	COD < 100 ppm
TDS	FO reject side concentration up to 200,000 ppm	RO reject concentration up to 80,000 ppm
Pre-treatment	Micron filters of suitable rating are sufficient	Ultrafiltration (UF) is recommended
OPEX	Significantly low OPEX thereby reducing the payback period	High OPEX