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Abstract In this paper, a forward osmosis (FO) process has been proposed to extract clean water from the micro-polluted feed containing heavy metal ions using biogas slurry as the draw solution, and then the diluted biogas slurry was directly utilized as a hydroponic solution to cultivate rice and leek without further treatment. In this process, the Cd2+ and Pb2+ ions, in the feed solution were effectively blocked by the FO membrane and the rejection coefficients were high to 98.5% and 97%, respectively. On basis of the high performance of FO membrane, the operation parameters of the FO process were optimized. Under the optimized conditions, the FO process can extract enough clean water to dilute the biogas slurry, and the diluted biogas slurry can promote rice and leek to grow. The growth of the rice and leek in the diluted biogas slurry confirmed that the use of FO process is an effective way in water recovery and reuse for agricultural processes. Graphical abstract Schematic diagram of Biogas slurry-drawn FO experimental apparatus. fx1 Highlights • Pollution-free biogas slurry was used as draw solution of forward osmosis. • The rejection coefficients of Cd2+ and Pb2+ were high to be 98.5% and 97%, respectively. • Rice and leek cultivated with diluted biogas slurry grew well. • The operation parameters of forward osmosis process were optimized. [ABSTRACT FROM AUTHOR]