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## Prediction and NMR Determination of Fluid-Film Thickness and Velocity Distribution in Nitrifying Trickling Filters

**EPA 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:**Jones, Brandon

**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

### Objective:

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.

### Approach:

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.

### Supplemental Keywords:

*fellowship, probability density function, PDF, total ammonia nitrogen, nuclear magnetic resonance, NMR.*, RFA, Scientific Discipline, Air, Sustainable Industry/Business, Air Pollution Control, air toxics, cleaner production/pollution prevention, Chemistry, Hazardous Waste, Chemistry and Materials Science, Engineering, Engineering, Chemistry, & Physics, Environmental Engineering, biofiltration, emission control strategies, hazardous waste treatment, emission control technologies, VOCs, biofilter, emission controls, remediation, probability density function, Volatile Organic Compounds (VOCs), biofiltration systems, air emissions, removal