Reverse Osmosis Concentrate for Sustainable Food and Bioenergy Production

This study explores application of reverse osmosis concentrate for developing a synergy between aquaculture and halophyte agriculture to ensure food and biofuel security in the urban context. The experimental setup comprised of two tanks, top and bottom connected through uPVC pipe and a pump for saline water recirculation. Panicum antidotale were grown from seeds and transferred into uPVC pots with holes at bottom for infiltration. After acclimatization period, 6 planted pots were placed in the top tank, while the bottom tank was filled with saline water that was concentrate of a reverse osmosis (RO) system. The water was aerated and a commercial fish species was added. A parallel setup was established as a control using tap water. The fish water was circulated 4 times a day. Growth of plants in RO concentrate with fish excreta was 8 percent higher as compared to the control sample. Overall, plant growth was better in saline water as compared to control and vice versa for the fish growth. Fish survival rate was 100% and average weight of fish in saline water was 309.5 grams while that in the control was 424.4 grams. The growth of fish was better in the control than in saline water, from an initial average length 7 cm to 75.4 cm in saline water and 88.7 cm in the control sample, respectively. Biomethane was successfully produced by co-digestion of halophyte with cow manure in 1:1 ratio. The developed system illustrates application of concentrate water for food and bioenergy production.