GRANULATION OF DIGESTED SEWAGE-SLUDGE IN MESOPHILIC UASB REACTORS TREATING DISTILLERY WASTE-WATERS FROM SUGAR-CANE MOLASSES

Five 4.02-1 UASB (Upflow Anaerobic Sludge Blanket) reactors were conti nuously operated at 30-degrees-C under different hydrodynamic regimes for more than 120 days. The effect of the upflow liquid velocity (ULV) over the range of 0.25 to 2.0 m/h on the biological characteristics o f the granules formed by treating vinasses (waste water of alcohol dis tilleries) from sugar cane molasses was investigated constantly mainta ining the volumetric loading rate (VLR) (8 g COD/l . d). Granular slud ge was found at all the ULV tested. The size, shape, etc., of the gran ules indicated that the ULV had a considerable effect on the sludge cu ltivated in this type of system, thereby acting as a selection process for the biomass. The best results in relation to the time of appearan ce, size, shape, consistence, stability, composition, and the accumula tion were observed in the ULV range between 0.25 and 0.5 m/h. Microsco pic studies of the granules using optical and epifluorescence microsco pes and the scanning electron micrograph (SEM) showed a heterogeneous biomass and revealed the cell characteristics.