Enhancing the petformance level and efficiency of existing WWTPs has been an important area of research and investigation over the past decade. Several attempts have been directed towards developing computer tools for modeling and control of these plants. GPS-X program was used in this research to study the petformance of the activated sludge module of Gabal EL Asfar WWTP in Cairo, Egypt, one of the landmark projects not only in the Middle East but worldwide. This plant is designed to treat a sewage flow rate of 1.0 million m3/d for the first stage. Samples were taken from different locations at the plant and tested at the American University in Cairo to validate the experimental results for biological oxygen demand (BODs), chemical oxygen demand (COD), suspended solids (SS) and dissolved oxygen (DO) with those obtained from simulating the plant operation by the GPS-X program. Different scenarios were then simulated out through a series of sensitivity analyses for summer and winter. These included the increase in the flow rate (Q) from the actual value up to 1.8Q, variation in the recycle ratio over the range of 0.3 to 1.0, variation of the underflow rate from the primary tanks from 300 to 2000 m3 /d, the variation in the wastage flow rate from 1000 to 5000 m3/d, and variation in the aeration power from 55 to 95 KW under two different temperatures for summer (28°C) and winter (20°C). These variables were chosen because they mostly affect the operational petfonnance level of the activated sludge process.

The results showed that it is possible to increase the flow rate in summer up to 1.2Q and in winter up to l .4Q without adversely affecting the effluent concentrations of key WW parameters, removal levels of which remained at > 80%. In addition, using an aeration power within the range of 55- 65 KW (actual condition, 60 KW)

would provide the required amount of DO in the aeration tanks for summer and winter. This suggests that savings in energy could be realized versus the current operating conditions. In case the flow does not vary seasonally, then a recycle ratio of 0.40 instead of 0.68 would be recommended in summer to reach the desirable DO concentration of 2.0 mg/l, resulting in further savings in terms of requirements for pumping the sludge from the final clarifiers to the aeration tanks. A recycle ratio of 0.94 instead of 0.68 would be recommended in winter to retain the same level of DO. Moreover, the wastage sludge flow rate could be reduced from 3000 to 2000 m3/d in summer and from 2353 to 2000 m3/d during winter to save the energy required for pumping as well as decreasing the amount of sludge pumped to the wastage line without affecting the effluent quality of the treated wastewater. Consequently, a better performance of the plant could be accomplished along with a decrease in the operational cost.


School of Sciences and Engineering


Interdisciplinary Engineering Program

Date of Award


Online Submission Date


First Advisor

Edward Smith

Committee Member 1

Hamdy Ibrahim Ali

Committee Member 2

Abdallah Bazaraa

Committee Member 3

Ezzat Fahmy

Document Type



193 leaves :

Library of Congress Subject Heading 1

Sewage disposal plants.


The author retains all rights with regard to copyright. The author certifies that written permission from the owner(s) of third-party copyrighted matter included in the thesis, dissertation, paper, or record of study has been obtained. The author further certifies that IRB approval has been obtained for this thesis, or that IRB approval is not necessary for this thesis. Insofar as this thesis, dissertation, paper, or record of study is an educational record as defined in the Family Educational Rights and Privacy Act (FERPA) (20 USC 1232g), the author has granted consent to disclosure of it to anyone who requests a copy.

Call Number

Thesis 2002/79



Included in

Engineering Commons