Biochemical Oxygen Demand (BOD) analysis is the test everyone loves to hate—and for compelling reasons. The test has a number of disadvantages: a five-day incubation period, extensive sample preparation and, often, difficulties in obtaining consistent repetitive values.
Most wastewater treatment plant laboratories currently use membrane-based probes to measure dissolved oxygen (DO) in the BOD5 Procedure. Before the development of these probes, labs typically used a titration method, which was a lot more complicated and time consuming. Although membrane DO probes took some of the hassle out of BOD measurement procedures, they came with their own set of hassles, according to Jill Bolin, Laboratory Manager for the Water Utilities Department of Nacogdoches, Texas.
“We had a lot of drift on our probes because the membranes would constantly be fouling. This was causing major problems with our blanks coming in. We had calibration issues with the probes, too. We would always be cleaning, recalibrating the probes, and replacing the membranes to try solve the problems.”