For the BOD reduction analysis in a trickling filter, two methodologies are available, the NRC equations and the Velz-Schultz methodology. Which should be used and is more accurate?
The Velz-Schultz equations were developed for more modern media, which is plastic media. The NRC equations are more widely used and generally accepted for BOD reduction analysis, but the Velz-Schultz equations more accurately take into consideration the type of media and media characteristics than the NRC equations. Simply put, for plastic (vertical or crossflow) media, the Velz-Schultz equations are more accurate, whereas the NRC equations apply more to other types of media (rock, stone, wood, etc).
