Your, host, Dr. Deb, outlined why we measure BOD (biochemical oxygen demand), why it's often done for five days (five days along the Thames from London to the North Sea), how the test is completed, and what we do with the data (wasteload allocations). She also explained why this archival test is still useful when we have gas chromatographs and other high-tech laboratory instrumentation. This show is part of a set of shows on water quality testing (see/hear also 5/10/09 and 3/15/09 on "Water, Water Everywhere".