OXYGEN-TRANSFER LIMITATION IN A RESPIROMETER

The oxygen uptake process in a respirometer was analyzed by a mathemat ical model consisting of oxygen transfer accompanied with oxygen consu mption reaction. The criterion to avoid an oxygen-transfer limitation was derived on the basis of the ratio of the maximum biochemical react ion rate to the maximum possible oxygen-transfer rate. The maximum bio chemical reaction is described by the first-order rate equation, where as the maximum possible oxygen-transfer rate is calculated by multiply ing the oxygen-transfer coefficient with the solubility of oxygen in w ater. An oxygen-transfer coefficient in a respirometric reactor was es timated as 1.8 h(-1), by using the model analysis of an oxygen uptake data from the same reactor. A simplified criterion for a respirometer without oxygen-transfer limitation is then obtained as XS much less th an 16.51/K-1, where X and S represent concentration of biomass and sub strate, respectively, and K-1 is the first-order rate constant, (L/mg VSS)/h.