Dissolved Oxygen-Stat Titration Respirometry: Principle of Operation and Validation

A method is presented to assess oxygen uptake rates which operates at constant dissolved oxygen concentration (DO). This method involves DO-stat titrations by controlled addition of a diluted H2O2 solution to a batch volume of activated sludge. The titrant flow rate is proportional to the biomass respiration rate, while the mass of H2O2 added is proportional to the oxidized organics. Classical batch respirometries (with and without gas flow, i.e., "open" and "closed") were compared to the DO-stat technique using first NaSO2 as reducing chemical and then respiring aerobic biomass. An excellent correlation was found among estimates of oxygen consumption rate and short term yield coefficient by the three techniques. Inhibition by H2O2 was found to be negligible for biomass concentration as volatile suspended solids of =>1.5-2 g/L.