Photo fermentative biohydrogen production potential using microalgae-activated sludge co-digestion in a sequential...

Area of Science:

• Biotechnology and Bioenergy
• Sustainable Energy Production
• Microalgal Cultivation

Background:

• Biohydrogen (bioH₂) offers a carbon-free energy alternative, producible from microalgae via photolytic and anaerobic digestion (AD) pathways.
• Scaling up AD for bioH₂ production presents challenges, particularly with continuous stirred tank reactors (CSTRs) and sequential flow batch reactors (SFBRs).

Purpose of the Study:

• To analyze the performance characteristics of an SFBR for biohydrogen generation.
• To evaluate the feasibility of using a Chlorella vulgaris and domestic wastewater activated sludge (WWAS) co-culture in an SFBR system.

Main Methods:

• Co-cultivation of Chlorella vulgaris and WWAS in an SFBR under anaerobic conditions with light.
• Operation at an organic loading rate (OLR) of 4.7 g COD L^-1 day^-1 and a hydraulic retention time (HRT) of five days.
• Maintenance of pH at 6 for a 15-day incubation period.

Main Results:

• Maximum bioH₂ concentrations reached 421.1 μmol L^-1 (exponential phase) and 56.6 μmol L^-1 (steady-state phase).
• High acetate concentrations (average 11.9 g L^-1) were observed in the effluent during the steady-state phase.
• BioH₂ production was consistent but inadequate, with a logistic function model showing the best fit for prediction.

Conclusions:

• SFBR operation with constant OLR yielded consistent, albeit insufficient, bioH₂ production.
• Optimizing OLR and HRT in SFBRs may offer a more feasible approach for upscaling bioH₂ yield compared to CSTR limitations.
• The logistic function model is suitable for predicting bioH₂ generation in SFBR co-culture systems.