HYDROGEN MONITORING IN ANAEROBIC SLUDGE BED REACTORS AT VARIOUS HYDRAULIC REGIMES AND LOADING RATES

The dissolved hydrogen concentration was monitored in four laboratory-scale upflow sludge bed reactors. The upflow velocity (v(UP)) differed in each reactor, providing different hydraulic regimes. Five pseudo-steady-state conditions were applied to the four reactors. The dissolved hydrogen concentration increased proportionally with the organic loading rates (OLR) of the reactors, to attain values as high as 20 muM, while still remaining independent of the hydraulic regime. The experimental data yielded low hydrogen mass-transfer rates (k(L)a) and high ratios of the measured dissolved hydrogen concentration value to the equilibrium value calculated from the hydrogen partial pressure in the gas phase (sursaturation factor): from 0.04 to 0.46 h-1, and from 19 to 102, respectively. Also, the increase in the v(UP) did not affect the hydrogen k(L)a nor the sursaturation factor. The k(L)a values showed a reasonable and positive correlation with the OLR values and the gas-flow rates, however no correlation was found between the sursaturation factor values and the latter parameters. This indicates that dissolved hydrogen concentration can not be predicted from hydrogen gaseous measurements in such reactors.