Hybrid pressure retarded osmosis-membrane distillation (PRO-MD) process for osmotic power and clean water generation

A novel pressure retarded osmosis-membrane distillation (PRO-MD) hybrid process has been experimentally conceived for sustainable production of renewable osmotic power and clean water from various waters. The proposed PRO-MD system may possess unique advantages of high water recovery rate, huge osmotic power generation, well-controlled membrane fouling, and minimal environmental impacts. Experimental results show that the PRO-MD hybrid process is promising such that not only it can harvest osmotic energy from freshwater but also from wastewater. When employing a 2 M NaCl MD concentrate as the draw solution, ultrahigh power densities of 31.0 W m(-2) and 9.3 W m(-2) have been demonstrated by the PRO subsystem using deionized water and real wastewater brine as feeds, respectively. Simultaneously, high-purity potable water with a flux of 32.5-63.1 L (m(-2) h(-1)) can be produced by the MD subsystem at 40-60 degrees C without any detrimental effects of fouling. The energy consumption in the MD subsystem might be further reduced by applying a heat exchanger in the hybrid system and using low-grade heat or solar energy to heat up the feed solution. The newly developed PRO-MD hybrid process would provide insightful guidelines for the exploration of alternative green technologies for renewable osmotic power and clean water production.