Relative effect of different inorganic acids on selective enrichment of acidogenic biocatalyst for fermentative biohydrogen production from wastewater

摘要

The effect of different inorganic acids viz., HNO_3, HCl, H_2SO_4 and H_3PO_4 on inoculum pretreatment to selectively enrich hydrogen (H_2) producing acidogenic bacteria was evaluated in anaerobic sequencing batch bioreactors. Relative positive efficiency of HNO_3 pretreated consortia in enhancing H_2 production (11.85molH_2/kgCOD_R) was noticed compared to other acids (HCl, 5.64molH_2/kgCOD_R; H_2SO_4, 7.65molH_2/kgCOD_R; H_3PO_4, 6.90molH_2/kgCOD_R) and untreated-parent consortia (control, 6.80molH_2/kgCOD_R). On the contrary, substrate degradation (COD removal) was higher with the control operation (ξCOD, 66.3%; substrate degradation rate (SD_R), 1.42kgCOD_R/m~3-day) compared to pre-treated culture. HNO_3 pre-treatment resulted in a shift in the fermentation pathway towards more acetic acid production, while other acid pretreatment and untreated culture showed mixed type fermentation (acetic, butyric, propionic acids). The bio-electrochemical analysis and dehydrogenase activity supported the biocatalyst performance after HNO_3 pretreatment with specific enrichment of Firmicutes and Bacillus.