Granulation is an important characteristic of sludges used in upflow a
naerobic sludge blanket (UASB) reactors. As the UASB technology is rap
idly spreading, there is a need of granular sludge for inoculation of
new reactors, particularly in those countries where anaerobic technolo
gies have been just recently accepted. Alternative sources of inocula
are digested sludge, digested manure, septic tank sludges and pond sed
iments. Raw waste activated sludges have also been identified as a con
venient material for reactor seeding, with previous treatment In this
work, anaerobic flocculant sludge obtained from raw waste activated sl
udge has been granulated with hydraulic stress, in a lab-scale column
under different upflow velocities (1 to 50 m h(-1)). A methodology is
proposed for enhancing the quality of non granular anaerobic sludges i
n batch treatments of less than 8 hours. The granular sludge produced
was used as inoculum for a UASB lab scale reactor. The seed sludge imp
roved all its characteristics and maintained the granulation, in spite
of the low velocity (0.08 m h(-1)) applied.