Application Note

Bringing Efficiency And New Confidence To BOD5 Analysis

By Bob Dabkowski, Hach Company

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."

Bolin has been the laboratory manager for the city's water utilities department for the past 15 years and she recently received the Laboratory Analyst Excellence Award from the Water Environment Federation (WEF). Her laboratory analyzes the influent and effluent flows and wastewater treatment process controls for the wastewater treatment plant, as well as industrial effluent samples being discharged into the plant.