This study investigated the possibilities of improving biogas yield from anaerobic digestion of refinery activated sludge (RAS) by optimizing the food to microorganism (F/M) ratio. Different F/M ratios of 0.25, 0.50, 1.00 and 2.00 were studied. The highest biogas production (147.98±7.40 ml/gvs), methane production (51.41±1.78 ml/gvs) and methane content (42.00±5.90%) were obtained from the F/M ratio of 1.00 followed by 0.50, 0.25 and 2.00, respectively. The phytotoxicity of biosolids that came

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... rom anaerobic digestion was also evaluated using three different types of seed (Vigna radiata, Brassica rapa and Lycopersicon esculentum) during this process. Increasing amount of RAS via increasing of the F/M ratio (0.25-1.00) stimulated plant development (GI>100) and reduced the phytotoxicity of RAS.