Hydraulic Characteristics of Upflow Anaerobic Filters

Abstract

Tracer studies are conducted to characterize the hydraulic behavior of upflow anaerobic filters at Reynold's numbers less than 25. Tests are conducted with three different sizes of cross‐flow modular plastic media, providing a range of specific surface areas. Sections of this media are cut to fit a laboratory‐scale reactor, and a radioactive tracer is used to assess the residence time distribution under different flow conditions typical of those found in full‐scale systems. Tracer response curves are generated for various flow rates, and a computer model is developed to fit these curves. The best‐fit model parameters indicate that the extent of plug flow is positively correlated with the Reynold's number within the range tested. Hydraulic dead space increases with increasing Reynold's number. An increase in the plugflow behavior of the system also is associated with an increase in the specific surface area of the media. Gas bubbles passing through the media are found to produce complete mixing regardless of the media specific surface area. An agar coating used to simulate the presence of biological solids has little effect on the tracer response.