### Title page for ETD etd-07152005-084150

Type of Document Master's Thesis
Author Le, Trieu Van
Author's Email Address tle12@lsu.edu
URN etd-07152005-084150
Title Water Quality Modeling for Unconventional BOD
Degree Master of Science in Civil Engineering (M.S.C.E.)
Department Civil & Environmental Engineering
Donald Dean Adrian Committee Chair
Frank Tsung-Chen Tsai Committee Member
Zhi-Qiang Q Deng Committee Member
Keywords
• multi-order reaction
• BOD model
• least squares
• sedimentation
• scour
• benthic deposits
• BOD
• dissolved oxygen
• river pollution
• critical time
• second order reaction
• Douglas Fir
• TMDL
• biochemical oxygen demand
• respirometer
• reaction order
• three-halves order reaction
• streams
• kinetics
Date of Defense 2005-06-30
Availability unrestricted
Abstract
Predictions of the dissolved oxygen (DO) concentration in a stream are sensitive to the choice of Biochemical Oxygen Demand (BOD) reaction model which frequently is assumed to be first order, although published BOD data sets from analyses of samples from rivers show that many are described best by second order or three-halves order BOD reaction. Two DO models for a stream are developed, one with a second order and the other with a three-halves order BOD reaction. The DO equations are solved using Laplace transform method which simplifies the mathematical solution of the model equations by avoiding difficult to evaluate integrals. The DO sag equation incorporates exponential integral functions, calculated by exact or approximate series. The time at which the minimum DO concentration occurs is calculated numerically. The models are useful in calculating Total Maximum Daily Loads (TMDL) of streams.

In addition, this study examines change in stream water quality due to logging debris and leaf burden from forests which adds to BOD in the stream water and increases the sedimentation rate at which solids containing BOD are removed from the stream water. The first and second order BOD models included sedimentation are incorporated into a DO balance equation.

The BOD models are applied in remediation design examples using published BOD data collected from Douglas fir needles in stream water. Results obtained from data analysis shows that the logging debris data set is best described by second order BOD model. A treatment system designed based on second order BOD model to treat the logging debris wastewater before effluent is released.

BOD data, collected at daily intervals to five days from a respirometer for mixtures of glucose and glutamic acid, were tested using the root mean squared error method to determine their goodness-of-fit to three BOD reaction models: a first order model, a half-order model, and an order n model. The mixtures ranged in increments of 10% from 10% strength (90% dilution) to 100% strength (no dilution). There were ten replications of each strength of sample, so that the BOD of 100 samples measured at daily intervals were available.

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