An automated method for the measurement of oxygen uptake rates



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An automated method has been developed to determine the cumulative oxygen demands and oxygen uptake rates for wastewater samples. The apparatus consists of three modified commercially available manometer-type respirometers and a digital computer controlling the measurement process. The improved respirometers allow for discrete gas and liquid phase sampling, pH control, and gas composition control. The computer provides control of the respirometers and data reduction capabilities. The method represents significant advancements in pH control and speed of analysis over existing respirometric techniques. These improvements have allowed the respirometric method to become useful for the study of both carbonaceous and nitrogenous oxidation processes in wastewater. Several important factors influencing this measurement process are considered. The transfer of oxygen from the gas phase to the liquid phase and the exchange of gases between phases are investigated. Temperature, pH, and gas leakage are other factors examined. Details of respirometer design and computer interfacing are given. Data treatment and data reduction methods by the computer are discussed.