Anaerobic treatment of acidified and non-acidified substrata in UASB reactors

The selection of a suitable sludge which will be the inoculum of the reacto r is the first step in the start-up procedure of an anaerobic reactor. The sludge selected (inoculum) for this study was obtained from a UASB (Up-flow Anaerobic Sludge Bed) reactor used for the treatment of alcohol industry w astewaters. The industrial sludge was used in this work as the inoculum of two laboratory-scale UASB anaerobic reactors, which were fed with different substrata. The feed for the first reactor was acidified substratum (volati le fatty acid) and the second reactor was fed with non-acidified substratum (glucose). The purpose of this work was to study the effect of both substr ata in regular operation and to analyse the flotation problem which arises when the reactor is fed with a non-acidified substratum. Finally, the chara cteristics of the adapted sludge were studied and they were compared with t he initial inolucum (sludge). The following observations were noted in rela tion to the evolution of the sludge during operation: density, TSS content and C, H and N contents remained similar, but the particle size and VSS/TSS increased. The settling volume index decreased and methanogenic and acidog enic activities increased during operation in both reactors. The reactor fe d with volatile fatty acids was able to recover from unstable periods faste r than the reactor fed with a non-acidified substratum. The use of an acidi fied substratum avoided flotation, stabilised the system and reduced the so lid content in the effluent. Moreover, it worked properly with partially ac idified influents meaning a reduction in the chemical reactive expense requ ired to control acid pH-value throughout operation. (C) 1999 Society of Che mical Industry.