A Novel Biological Hydrogen Production System: Impact of Organic Loading

Proceedings WHEC2010
Hisham Hafez, George Nakhla, Hesham El Naggar, 
The University of Western Ontario, Canada


Abstract
The patent-pending system comprises a novel biohydrogen reactor with a gravity settler for
decoupling of SRT from HRT. Two biohydrogenators were operated for 220 days at 37 °C,
hydraulic retention time 8 h and solids retention time ranged from 1.4 to 2 days under four
different glucose concentrations of 2, 8, 16, 32, 48 and 64 g/L, corresponding to organic
loading rates of 6.5-206 kg COD/m3-d, and started up using anaerobically-digested sludge
from the St. Marys wastewater treatment plant (St.Mary, Ontario, Canada) as the seed. The
system steadily produced hydrogen with no methane. A maximum hydrogen yield of 3.1 mol
H2 /mol glucose was achieved in the system for all the organic loading rates with an average
of 2.8mol H2 /mol glucose. Acetate and butyrate were the main effluent liquid products at
concentrations ranging from 640-7400 mg/L and 400-4600 mg/l, respectively, with no lactate
detection.  Microbial community analysis using denaturing gradient gel electrophoresis
(DGGE) confirmed the absence of lactate producing bacteria Lactobacillus fermentum and
other non-hydrogen producing species, and the predominance of various  Clostridium
species.  Biomass concentrations in the biohydrogenators were steady, during the runs,
varying form 1500 mg/L at the OLR of 6.5 kg COD/m3-d to 14000 mg/L at the 104 kg
COD/m3-d, thus emphasizing the potential of this novel system for sustained stable hydrogen
production and prevention of biomass washout.