Prediction and NMR Determination of Fluid-Film Thickness and Velocity Distribution in Nitrifying Trickling FiltersEPA Grant Number: U915193
Title: Prediction and NMR Determination of Fluid-Film Thickness and Velocity Distribution in Nitrifying Trickling Filters
Investigators: Krumins, Valdis J.
Institution: University of Maryland - College Park
EPA Project Officer: Lee, Sonja
Project Period: January 1, 1997 through January 1, 2000
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1997) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Engineering and Environmental Chemistry , Fellowship - Agricultural Engineering
The objective of this research project is to develop and verify a mathematical model predicting the distribution of fluid-flow velocities and thicknesses in biological trickling filters.
In this work, a probability density function (PDF) is developed for the likelihood of finding a given flow (Reynolds number) over a unit of packing. The model predicts an exponential relationship between the Reynolds number and the probability of finding that flow rate. Wetted area, minimum flow rate to wet the packing material, and maximum flow rate before flooding of the packing material are calculated using methods presented by other authors. The PDF is subject to the constraints that the sum of probabilities for all nonzero flow rates must equal the wetted fraction, the sum of all local flows must equal the total flow applied to the filter, and only Reynolds numbers between the minimum and maximum are possible.
Miniature trickling filters (25.4 mm diameter with 6.4 mm spherical polystyrene packing) are used to verify the model. Nitrifying biofilms were allowed to form on six of the biofilters by circulating a nutrient solution containing 2 mg/L total ammonia nitrogen for several months. Six additional biofilters are observed without biofilm. Nuclear magnetic resonance (NMR) is used to image the biofilters as the nutrient medium is trickled through at one of three superficial flow rates: 75 m/d, 150 m/d, and 300 m/d. The NMR images show the location of biofilm, packing media, and water, and also display the velocity of any flow.