Abstract
The aim of the present work was to study the maximum potential methane production in batch assays of
sludge samples taken along the operation of two EGSB reactors (RI inoculated with granular sludge and RII
inoculated with suspended sludge) fed with increasing oleic acid concentrations between 2 and 8 gCOD/l
(HRT=1 day). After removing the residual substrate, the sludge was incubated in batch vials without any
added carbon source. A maximum methane production rate of 152±21 mlCH4(STP)/gVS.d was obtained for the
RII-suspended sludge taken on day 70, when oleate at a concentration of 2 g COD/l was fed with a cosubstrate
(50% COD). The maximum plateau achieved in the methane production curve was 1145±307
mlCH4(STP)/gVS, obtained for the RII-suspended sludge taken on day 162, when oleate was fed as the sole
carbon source at 6 g COD/l. Methanization rate of the adsorbed substrate was enhanced under stirring
conditions and was inhibited by adding oleic acid. Extraction and GC analysis confirmed that the main
adsorbed substrate was palmitate, and not oleate, as previously suspected. These results evidence the
advantage of sequencing adsorption and degradation cycles for the treatment of effluents with high lipid
content.
Keywords:
EGSB, Granular sludge, LCFA, Oleic acid, Palmitic acid
Publication Type: Papers in Conference Proceedings