A web-enabled software for real-time biogas fermentation monitoring – Assessment of dark fermentations for correlations between medium conductivity and biohydrogen evolution

A web-enabled software was developed for continuous online monitoring of biohydrogen, biomethane and carbon dioxide gas fractions, temperature, Dissolved Oxygen (DO), pH, conductivity and gas volume for biogas fermentations. The cumulative gas volumes are computed recursively at 1 min intervals. Process data streamed into a MySQL database are accessible on a Local Area Network in real-time. This software was evaluated via continuous monitoring of two batches of dark fermentations for biohydrogen production using anaerobic sludge as inoculum and glucose as substrate. The effect of sampling frequency on the accuracy of cumulative hydrogen volume determination and the possible correlations between medium conductivity and biohydrogen evolution were examined. Data showed an erroneous over estimation of biohydrogen production at 12.09% and 16.23% for 12 and 24 h sampling intervals, suggesting the adoption of a high sampling rate to derive reliable key process parameters from the Gompertz model. Partial correlations were observed between medium conductivity and hydrogen gas fractions with maximum conductivity changes of 5.0 and 21.1 S × cm−1, corresponding to peaks of hydrogen concentrations of 33.53% and 44.86%, respectively. Accurate application of conductimetric techniques for real-time monitoring of biohydrogen production requires further understanding of all sources of conductivity changes. The implemented software could generate high throughput actionable information for biohydrogen process development and optimization.