Continuous measurement of dissolved H₂ in an anaerobic reactor using a new hydrogen/air fuel cell detector

A miniature fuel cell, using a hydrophobic Teflon® membrane, designed to continuously measure dissolved H₂ in nonbiological media, was tested for use in anaerobic digestion conditions. In water, this detector responds quickly and efficiently to variation of hydrogen concentration in the range from 80 to 770 nM The media used, and the metabolites or products found in anaerobic digestion media, i. e. inorganic carbon and phosphate buffers, formate, acetate, and dissolved methane, did not interfere with the signal of the detector cell. Dissolved hydrogen sulfide did not poison the cell but was detected. In spite of the detector's high sensitivity to hydrogen (about 21,000 times higher for hydrogen than for hydrogen sulfide), interferences can occur in media containing high sulfide levels. In a methanogenic reactor, the detector cell response to dissolved hydrogen was fast and reliable with time. The observed values ranged values ranged from 2 to 3.5μM. Dissolved hydrogen concentrations were 40 to 70 times higher than values calculated from measured hydrogen partial pressures and Henry's coefficient, suggesting a limitation of the process in the hydrogen transfer from the liquid to the gaseous phase.