Date of Award


Document Type


Degree Name

Master of Science (MS)


Civil and Environmental Engineering

First Advisor

Dr. Wal id EI- Shorbagy

Second Advisor

Ronald L. Droste

Third Advisor

Dr. A.M .O. Mohamed


A mathematical framework is developed for use in the optimal sizing of a wastewater treatment system comprises an activated sludge system preceded by a primary clarifier. Mathematical models predicting the performance of various unit processes are used to construct the system model. ASM3, used in the developed framework, is among the most recent and comprehensive models that closely describe the biological reactions taking place in the activated sludge system. Cost information functions including capital and operational costs of different system units are also modeled. An optimization problem is formulated with the objective to produce optimal sizes of different units with least cost and meeting the effluent requirements. The problem is a nonlinear programming problem that is solved using the General Algebraic Modeling Systems software "GAMS". The optimization model is applied to an illustrative problem producing valuable and practical results. The model is also used as an analysis tool to reveal the influence of various involved parameters and inputs upon the system performance and relevant results. Uncertainty consideration is also highlighted with an example showing an expected-value problem. Important insights about process design, modeling, and integration were gained by exercising the model. Such include the effectiveness of each unit operation, the importance and effect of sludge retention time, the effect of temperature on model performance and cost, and the effect of influent characteristics variability. Huge cost savings can be achieved by controlling the system at different temperatures. Influent characteristics variability is of great importance and considering such at the design stage contributes significantly to the designed system optimality and reliability.