Exploring hydraulic and organic overload effects in a xylose-fed SBR

Abstract

This study compares the impact of hydraulic and organic overload in a sequential batch reactor (SBR) fermenting xylose as substrate. Before overloading (SBR reference, SBR-R), the system was operated with an HRT of1 day and an OLR of 12 g COD/L·d, resulting in a SRT of 3.5 days, with complete xylose conversion and a considerable caproic acid production (0.11 Cmol/Cmol-s. Decreasing HRT (hydraulic overload) in SBR-H (HRT 0.5 days; OLR 24 g COD/L·d) led to non biomass retention (HRT=SRT), lower xylose conversion (65%) and negligible caproic acid formation. In contrast, doubling the feeding xylose concentration (organic overload) in SBR-O (HRT 1 day; OLR 24 g COD/L·d) resulted in a similar performance as the SBR-R with lower SRT (2.5 days) and higher butyric acid production. Results suggest the system under the conditions applied is more sensitive to the hydraulic overload than to the organic overload.