ORP Measurement in Anaerobic Systems Using Flow‐Through Cell

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Abstract
A new method was developed using a flow‐through cell for the measurement of oxidation‐reduction potential (ORP) for anaerobic microbial cultures. The method involves passing the reactor effluent through a recycle line equipped with an ORP probe. Stable ORP values were obtained for two different anaerobic reactors, operating under steady‐state conditions, for more than 2 months. One of the reactors was strictly methanogenic and the other was sulfate‐reducing. A comparison of ORP measurements by this method with conventional measurement techniques showed this method minimizes uncertainty in the measurement as a result of hydrodynamic limitations, temperature changes, and oxygen contamination of the sample. It prevents fouling of the ORP probe by allowing for easy cleaning of the probe and checking for calibration before use. The method can also be used for both batch reactors and chemostats (CSTR).