Author(s): Kyazze G, Dinsdale R, Guwy AJ, Hawkes FR, Premier GC,
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Abstract The performance of a mesophilic two-stage system generating hydrogen and methane continuously from sucrose (10-30 g/L) was investigated. A hydrogen-generating CSTR followed by an upflow anaerobic filter were both inoculated with anaerobically digested sewage sludge, and ORP, pH, gas output, \%H(2), \%CH(4) and \%CO(2) monitored. pH was controlled with NaOH, KOH or Ca(OH)(2). Using NaOH as alkali with 10 g/L sucrose, yields of 1.62 +/- 0.2 mol H(2)/mol hexose added and 323 mL CH(4)/gCOD added to the hydrogen and methane reactors respectively were achieved. The overall chemical oxygen demand (COD) reduction was 92.6\% with 0.90 +/- 0.1 g/L sodium and 316 +/- 40 mg/L residual acetate in the methane reactor. Operation at 20 g/L sucrose and NaOH as alkali led to impaired volatile fatty acid (VFA) degradation in the methane reactor with 2.23 +/- 0.2 g/L sodium, 1,885 mg/L residual acetate, a hydrogen yield of 1.47 +/- 0.1 mol/mol hexose added, a methane yield of 294 mL/gCOD added and an overall COD reduction of 83\%. Using Ca(OH)(2) as alkali with 20 g/L sucrose gave a hydrogen yield of 1.29 +/- 0.3 mol/mol hexose added, a methane yield of 337 mL/gCOD added and improved the overall COD reduction to 91\% with residual acetate concentrations of 522 +/- 87 mg/L. Operation at 30 g/L sucrose with Ca(OH)(2) gave poorer overall COD reduction (68\%), a hydrogen yield of 1.47 +/- 0.2 mol/mol hexose added, a methane yield of 138 mL/gCOD added and residual acetate 7,343 +/- 715 mg/L. It was shown that sodium toxicity and overloading are important issues for successful anaerobic digestion of effluent from biohydrogen reactors in high rate systems. (c) 2006 Wiley Periodicals, Inc.
This article was published in Biotechnol Bioeng
and referenced in Journal of Fundamentals of Renewable Energy and Applications