The Performance and Modeling of Methanol- & Glycerin-fed Deep Bed Denitrification Filters
Authors:
- Katya Bilyk, P.E. - Hazen and Sawyer
- Peter Dold - EnviroSim
- Samuel Ledwell - EOS
The purpose of this paper is to summarize a successful denitrification filter modeling approach and explain how the results of this effort have enhanced our understanding of denitrification filter design and operation.
Denitrification filters are a fixed film process that is often used to remove nitrate from nitrified effluents to low levels. The traditional design method for sizing these units is based on either hydraulic loading rate (HLR), nitrate loading rate (NLR), or some combination of the two; and ignores other variables that also influence denitrification filter performance such as temperature, carbon dose, carbon type, and dissolved oxygen. These variables are included in the BioWin™ fixed-film element.
The authors have successfully calibrated BioWin™ models to denitrification filter performance from four different facilities. The calibration approach used to model the following plants, as well as observations that have enhanced our understanding of filter design and operation, will be discussed:
• Plant A – dynamic calibration to three months of full-scale stress-test data
• Plant B – dynamic calibration to 15-minute online instrumentation data for a one week period, including carbon dose, flow, and nitrate concentration in/out of the filter.
• Plant C – steady state calibration to vertical nutrient profiles through a pilot filter column
• Plant D – steady state calibration to winter and summer operations
The following are some of the observations that will be discussed:
• Glycerin can be successfully utilized on denitrification filters provided the proper operational adjustments are made.
• Among filters operating in a trim-mode, nitrate removal across the filters is similar at HLRs of 2 gpm/sf and 3 gpm/sf.
• Filter backwashes are accompanied by a significant reacclimation period, and performing these timer-initiated backwashes during low load conditions is expected to reduce the duration of the reacclimation period.
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