Influence of crude glycerol load and pH shocks on the granulation and microbial diversity of a sulfidogenic Upflow Anaerobic Sludge Blanket reactor

• DOI: 10.1016/j.psep.2019.11.005
• Publication Date: 2019-11-12T17:05:32Z
• Authors: M. Mora; J. Lafuente; D. Gabriel
• Keywords: Crude glycerol; 13. Climate action; SO2 valorization; Sludge bed stratification; Sulfidogenesis; UASB; 01 natural sciences; 7. Clean energy; SRB; 6. Clean water; 0105 earth and related environmental sciences

Bioscrubbers are an environmental-friendly alternative to valorize SO2 contained in flue gases to obtain elemental sulfur as final value-added product. The bottleneck of a SO2 bioscrubber relies on the heterotrophic reduction of the absorbed SO2 to obtain sulfide. In this study, the performance and stability of a sulfidogenic Upflow Anaerobic Sludge Blanket reactor (UASB) using crude glycerol was investigated during 6 months of operation under variable organic loading rates. The UASB presented a maximum elimination capacity and a sulfate removal efficiency of 110 mg S-SO42- L-1 h(-1) and 100%, respectively, when the chemical oxygen demand to sulfate ratio (COD/S-Sulfate) was 8.5 g O-2 g(-1) S-SO42-. The intermediate compounds identified from crude glycerol degradation were mainly propionic and acetic acid, which varied along the sludge bed together with the pH. Microbial diversity analyses of the sulfidogenic granular sludge showed that the most abundant sulfate reducing genera were Desulfovibrio spp. and Desulfobulbus spp. Methanosaeta and other fermentative/acidogenic microorganisms were also found in significant amounts. Particle size distribution analyses showed that biogas production allowed the granulation of the sulfidogenic sludge, which had an average particle size ranging from 729.3 mu m (lower part of the bed) to 391.7 mu m (upper part of the test). A short-term pH shock caused a detrimental effect over the system performance due to degranulation. Concomitantly, biogas production was interrupted and acetic acid was accumulated also causing a significant impact on microbial diversity. Unclassified Clostridiales, Desulfovibrio spp. and Desulfobulbus spp. showed a higher resistance to pH shocks.