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Increased biological hydrogen production with reduced organic loading.
Steven W Van Ginkel1, Bruce Logan
1Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett Building, University Park, PA 16801, USA.
Water Research
|September 1, 2005
Summary
Lowering organic loading rates and using dilute feeds optimizes hydrogen production in chemostat reactors. This approach enhances hydrogen yield by promoting acetate production and preventing biomass washout, crucial for efficient biohydrogen processes.
Area of Science:
- Biotechnology and Bioengineering
- Renewable Energy Production
- Microbial Physiology
Background:
- Chemostat reactors are utilized for continuous microbial cultivation and bioprocess optimization.
- Hydrogen (H2) production is influenced by various operational parameters, including organic loading and hydraulic retention time (HRT).
- Understanding the interplay between substrate concentration, loading rate, and reactor performance is critical for maximizing H2 yields.
Purpose of the Study:
- To investigate the impact of organic loading rate and HRT on H2 production in chemostat reactors.
- To determine the optimal conditions for maximizing hydrogen yield and glucose removal efficiency.
- To elucidate the role of microbial flocculation and metabolic byproducts in H2 production.
Main Methods:
- Experimental matrix varying HRT (1-10 h) and glucose loading rate (0.5-18.9 g/h) in chemostat reactors at 30°C and pH 5.5.
- Glucose concentrations in the feed ranged from 2.5 to 10 gCOD/L.
- Analysis of hydrogen yield, acetate:butyrate ratio, biomass concentration, and glucose removal efficiency.
Main Results:
- Hydrogen yield increased from 1.7 to 2.8 mol-H2/mol-glucose as the glucose loading rate decreased.
- Higher hydrogen yields correlated with a higher molar acetate:butyrate ratio, indicating preferential acetate production.
- Biomass flocculation enhanced reactor performance at higher glucose concentrations and reduced HRTs (2.5 h), enabling high glucose removal (>90%).
- Reduced HRT to 1 h at dilute conditions (2.5 gCOD/L) led to biomass washout due to insufficient flocculation.
Conclusions:
- Optimizing hydrogen yields requires operating at lower organic loading rates and more dilute feed conditions than typically employed.
- Biomass flocculation is a key factor for stable reactor operation at low HRTs and high substrate removal.
- The findings provide valuable insights for designing and operating efficient biohydrogen production systems.