creator Shaw, Andrew Robert advisor Pagilla, Krishna R. This research is focused on the half-saturation coefficient (KS), which is an important, but often overlooked, parameter in the Monod equation commonly used to describe biological wastewater treatment processes. Following an initial literature review, the research uses data for a denitrifying activated sludge process to show that KS is a function of the maximum rate and, further, that the relationship can be described either using a simple linear regression or by modeling diffusion explicitly. Building on this initial investigation of a particular treatment system, the research introduces and uses a “porter-diffusion” model that approximates diffusion to a linear equation for KS in the Monod equation. This is used to describe the linear relationship between KS and maximum rate for four different biological wastewater treatment systems. Finally, a sensitivity analysis is carried out on the parameters in the porter-diffusion model to show that r0 – a measure of cell size or diffusion distance – is the most sensitive parameter for a simple activated sludge process model based on a modified version of the International Water Association (IWA) activated sludge model #1 (ASM1). Overall this research has shown that in all of the biological wastewater treatment systems investigated in this thesis: (1) KS is not a constant but is a function of the maximum rate; (2) diffusion is a dominant mechanism that influences KS; (3) that a suitable expression for KS can be estimated using the porter-diffusion model, a linear data fit, or by modeling diffusion explicitly; and (4) measurements of KS in the laboratory must be carried out at the same food-to-microorganism (F/M) ratio as the full-scale system under investigation. Submitted by Erma Thomas (thomase@iit.edu) on 2015-09-17T16:02:06Z No. of bitstreams: 2 Shaw 2015 - INVESTIGATING THE SIGNIFICANCE OF HALF-SATURATION COEFFICIENTS ON WASTEWATER TREATMENT PROCESSES FINAL.pdf: 1300648 bytes, checksum: 91bca3191543b56f1680b0c7990ed21b (MD5) Shaw 2015 - Signed Cover Page.pdf: 21830 bytes, checksum: d435f01e64f561fd2e671e8258c9d2d0 (MD5) Made available in DSpace on 2015-09-17T16:02:06Z (GMT). No. of bitstreams: 2 Shaw 2015 - INVESTIGATING THE SIGNIFICANCE OF HALF-SATURATION COEFFICIENTS ON WASTEWATER TREATMENT PROCESSES FINAL.pdf: 1300648 bytes, checksum: 91bca3191543b56f1680b0c7990ed21b (MD5) Shaw 2015 - Signed Cover Page.pdf: 21830 bytes, checksum: d435f01e64f561fd2e671e8258c9d2d0 (MD5) Previous issue date: 2015-05 Ph.D. in Civil Engineering, May 2015 2015 2015-05 http://hdl.handle.net/10560/3554 en Dissertation born digital application/pdf In Copyright http://rightsstatements.org/page/InC/1.0/ Restricted Access CAEE / Civil, Architectural, and Environmental Engineering Illinois Institute of Technology Affiliated department