Dewatering of Brackish Water and Wastewater by an Integrated Forward Osmosis and Nanofiltration System for Direct Fertigation

Inorganic fertilizers, namely potassium chloride and monoammonium phosphate, have been used as draw solute for dewatering of brackish water and wastewater by forward osmosis (FO). A bench-scale unit with an ultra-low-pressure RO membrane was used. Moderate water flux was achieved for desalination of brackish water and wastewater concentration. Water flux using blended fertilizer was little lower than using individual fertilizers. Low reverse solute flux entailed negligible draw solute replenishment and eliminated eutrophication issues in feed disposal. Reversible fouling was observed with > 90% flux restoration. Partial recovery of draw solute by low-pressure nanofiltration process produced fertilizer solution with NPK content suitable for fertigation and hydroponics without any loss of precious draw solute. The integrated fertilizer-driven FO–NF system proved to be versatile and effective.