Biological H2 potential harvested from complex gelatinaceous wastewater via attached versus suspended growth culture anaerobes

•Suspended and attached growth exhibited different behavior for H2 production.•Attached needs less volume than suspended growth to achieve similar removal efficacy.•Net gain energy obtained from suspended growth is 4-folds higher than attached one.•Unlike lipase, activities of amylase and protease are higher in attached growth.

The effect of cultural growth treating gelatinaceous wastewater on hydrogen fermentative was assessed using up-flow multi-stage anaerobic sponge reactor (UMASR) and anaerobic sequencing batch reactor (AnSBR). Both reactors were operated at five hydraulic retention times (HRTs). UMASR achieved the maximum COD removal efficiency of 60.2 ± 4.4% at HRT of 48 h. Moreover, UMASR exhibited superiority in the course of carbohydrates and proteins removal efficiencies' of 100 and 52.5 ± 2.4% due to high amylase and protease activities' of 4.1 ± 0.3 and 0.032 ± 0.002 U, respectively. Contrariwise, AnSBR assigned for the peak hydrogen production rate of 1.17 ± 0.14 L/L/day at HRT of 24-h. Lipase activity was quite high (0.307 ± 0.023 U) in AnSBR resulting in removal efficiency of 35.2 ± 2.1% for lipids. Stover-Kincannon model emphasized that UMASR required lesser volume than AnSBR to sustain the same substrate degradation efficacy. Nevertheless, the net gain energy harvested from AnSBR surpassed UMASR by 4.0-folds at HRT of 24-h.