Role of calcium oxide in sludge granulation and methanogenesis for the treatment of palm oil mill effluent using UASB reactor

► Examine the treatability of POME and effects of CaO-CKD on the granulation process in UASB reactors. ► The main objective was to determine the influent CaO-CKD concentration and the relationship between the CaO concentration in the feed and biomass accumulation, specific granulation, methanogenic activity, and the density and composition of granules. ► The biomass concentration profiles along the reactors and the size distribution of granules were also measured to track and to assess granulation, methanogenesis, and COD removal on levels at the industrial scale. ► SEM micrograph are showing smooth surface of granule with a large opening cavities likely for biogas escape.