Parthiban Anburajan

Effects of anti-foaming agents on biohydrogen production

The effects of antifoaming agents on fermentative hydrogen production using galactose in batch and continuous operations were investigated. Batch hydrogen production assays with LS-303 (dimethylpolysiloxane), LG-109 (polyalkylene), LG-126 (polyoxyethylenealkylene), and LG-299 (polyether) showed that the doses and types of antifoaming agents played a significant role in hydrogen production. During batch tests, LS-303 at 100μL/L resulted in the maximum hydrogen production rate (HPR) and hydrogen yield (HY) of 2.5L/L-d and 1.08mol H2/mol galactoseadded, respectively. The following continuously stirred tank reactor operated at 12h HRT with LS-303 at 100μL/L showed a stable HPR and HY of 4.9L/L-d and 1.17mol H2/mol galactoseadded, respectively, which were higher than those found for the control reactor. Microbial community analysis supported the alterations in H2 generation under different operating conditions and the stimulatory impact of certain antifoaming chemicals on H2 production was demonstrated.

High-rate hydrogen production from galactose in an upflow anaerobic sludge blanket reactor (UASBr)

High-rate hydrogen production from galactose and rapid granule formation were achieved in a mesophilic (37 °C) upflow anaerobic sludge blank reactor (UASBr). Hybrid immobilized cells were seeded to a CSTR fed with galactose (15 g L−1) at a hydraulic retention time (HRT) of 12 h for 12 days, after which the mixed liquor from the CSTR was transferred to the UASBr. Rapid granule formation was observed after 5 days of initial UASBr operation at 6 h HRT and further enhanced at 3 h HRT. The peak hydrogen production rate (HPR) and hydrogen yield (HY) of 32.7 L L−1 d−1 and 1.95 mol mol−1 galactose were attained at the HRT of 3 h with an organic loading rate (OLR) of 120 g L−1 d−1. Microbial community analysis characterized by pyrosequencing of 16S rRNA genes showed that the proportion of Clostridium increased during the HRT at 3 h, whereas Bacilli proportions dominated at 6 h HRT.

Recovering hydrogen production performance of upflow anaerobic sludge blanket reactor (UASBR) fed with galactose via repeated heat treatment strategy

This study evaluated the effect of repeated heat treatment towards the enhancement of hydrogen fermentation from galactose in an upflow anaerobic sludge blanket reactor with the hydraulic retention time of 6h and the operation temperature of 37°C. The hydrogen production rate (HPR) and hydrogen yield (HY) gradually increased up to 9.1L/L/d and 1.1mol/mol galactose, respectively, until the 33rd day of operation. When heat treatment at 80°C for 30min was applied, hydrogen production performance was enhanced by 37% with the enrichment of hydrogen producing bacteria population. The HPR and HY were achieved at 12.5L/L/d and 1.5mol/mol hexose, respectively, during further 30 cycles of reactor operation. The repeated heat treatment would be a viable strategy to warrant reliable continuous hydrogen production using mixed culture.

Effect of 5-hydroxymethylfurfural (5-HMF) on high-rate continuous biohydrogen production from galactose

This study investigated the effect of 5-hydroxymethylfurfural (5-HMF) on high-rate continuous fermentative H2 production in a lab-scale fixed bed reactor (FBR) inoculated with mixed culture granules and fed with 15g/L galactose at a hydraulic retention time of 6h and at 37°C. During the 83days of operation, 5-HMF up to 2.4g/L was spiked into the feedstock. The maximum hydrogen production performance of 26.6L/L-d and 2.9mol H2/mol galactoseadded were achieved at 5-HMF concentration of 0.6g/L. 5-HMF concentration exceeding 0.9g/L not only inhibited hydrogen production but also affected the biofilm structure and microbial community population. However, when 5-HMF was eliminated from the feedstock, the performance and microbial community population were rapidly recovered.