An integrated fertilizer driven forward osmosis- renewables powered membrane distillation system for brackish water desalination: A combined experimental and theoretical approach

Utilization of an integrated forward osmosis-solar powered membrane distillation system can provide a promising method for brackish water desalination. In this study, the brackish water feed and fertilizer draw solutions were operated in a forward osmosis process to generate irrigation water for agriculture. Forward osmosis was also selected as membrane distillation pre-treatment to avoid fouling and wetting of the membrane distillation membrane. Subsequently, the diluted draw solutions were treated in the membrane distillation system to recover the initial osmotic pressure and to obtain a final distillate permeate. The experimental results revealed that the modified forward osmosis membrane exhibited slightly better performance in terms of maximum water flux, minimum reverse solute flux and high water recovery of 53.5%. In the membrane distillation process, an optimum water flux of about 5.7 L/m2. hr and high rejection rate of about 99.55% were achieved at an optimum temperature of 60 °C. Modelling was applied to investigate the feasibility of using a solar collector to power the membrane distillation system and hence limit energy costs. By using renewable energy, we calculate that the energy consumption of the hybrid system could be reduced by 67%. Membrane distillation-solar powered system can achieve optimum energy consumption recoded as 1.1 kWh. We concluded that the diluted fertilizer draw solution can be used as an irrigation water after further dilution by an available water source. By using forward osmosis prior to membrane distillation process, the membrane distillation membrane showed less fouling and wetting leading to excellent rejection rate and acceptable distillate permeate. The energy consumption of the forward osmosis-solar powered membrane distillation system was lower than that for reverse osmosis stand-alone system. The findings of this work could be used to develop guidelines for the optimal design of industrial forward osmosis-membrane distillation system.