| Summary: | Faculty of Science
School of Molecular and Cell Biology
9904041r
lthompson@csir.co.za === The production of H2 was monitored using an automated, semi-continuously fed anaerobic fluidised bed
bioreactor containing 2 facultatively anaerobic bacteria, Enterobacter cloacae (E. cloacae Ecl) and
Citrobacter freundii (C. freundii Cf1). Shake flask tests using Endo formulation with modified C:N:P ratios,
showed that a 334:28:5.6 ratio gave the highest attached counts of E. cloacae Ecl and C. freundii Cf1 in
both single and binary species biofilms grown on granular activated carbon. Once the reactor had
achieved steady state after 30 days using the modified C:N:P ratio, pH, redox potential, temperature,
volatile fatty acids and the H2 production rate were monitored. The H2 production rate of 95 mmol H2 / (l x
h) compared favourably with previous studies. Bacterial biofilms counts for both E. cloacae Ecl and C.
freundii Cf1 remained high around 9.0 log cfu/g granular activated carbon, although biomass overgrowth
could not be controlled in the reactor. The efficiency of converting sucrose into H2 was calculated at
20.5%. Therefore use of this technology to power a 5.0kW proton exchange fuel cell for a single rural
household is currently not feasible due to the high organic load required. Pooling of wastewater
generation capacity, improvement of bacterial strain selection and feed formulation, pH control, gas
removal and purification are factors that need to be considered for future improvement of conversion
efficiencies. Use of this technology would be most suited for industrial processes generating large
volumes of wastewater high in carbohydrates. Alternatively, municipal wastewater treatment facilities
could be converted into electricity generating facilities through the combination of this technology and
proton exchange membrane fuel cells.
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