American Society of Civil Engineers


Mathematical Modeling of Encapsulated Buffer Performance in Sand Columns


by Lubo Liu, (Dept. of Civ. and Envir. Engrg., Univ. of South Carolina, 300 Main St., Columbia, SC 29208), Christine M. Rust, (Dept. of Envir. Health Sciences, School of Public Health, Univ. of South Carolina, Columbia, SC 29208), Joseph R. V. Flora, (corresponding author), (Dept. of Civ. and Envir. Engrg., Univ. of South Carolina, 300 Main St., Columbia, SC 29208 E-mail: flora-joseph @sc.edu), and C. Marjorie Aelion, (Dept. of Envir. Health Sciences, School of Public Health, Univ. of South Carolina, Columbia, SC 29208)

Journal of Environmental Engineering, Vol. 128, No. 12, December 2002, pp. 1128-1138, (doi:  http://dx.doi.org/10.1061/(ASCE)0733-9372(2002)128:12(1128))

     Access full text
     Purchase Subscription
     Permissions for Reuse  

Document type: Journal Paper
Abstract: A one-dimensional mathematical model was developed to simulate pH control using an encapsulated phosphate buffer during denitrification in a sand column. The parameters required for the model were obtained from direct physical measurement, from a tracer study to characterize the dispersion coefficient in the column, and from batch experiments designed to obtain an empirical expression describing the variation of the first-order rate constant for the encapsulated buffer core release with pH. First-order kinetic constants describing the rates of denitrification and ethanol biodegradation were obtained by fitting the model to column runs without the encapsulated buffer. With these parameters, the model was subsequently used to predict the performance of column runs containing the encapsulated buffer. Since denitrification was essentially complete in the sand columns, an increase in the effluent pH was observed. This pH increase was counteracted by the controlled release of the acidic core of the encapsulated buffers added in the columns. The model reasonably predicted the release of the encapsulated buffer core and the performance of the encapsulated buffer for controlling pH in the column.


ASCE Subject Headings:
Columns
Denitrification
Mathematical models
pH
Sand filters