European International Journal of Science and Technology Vol. 3 No. 5 June, 2014 29 Modeling Sewer Effluent Design Discharge with System Dynamics Technique *+ S.O. Ojoawo, # O.S Olaniyan and # A.A. Adegbola *Department of Civil Engineering, NMAM Institute of Technology, Nitte - 574110, Udupi District, Karnataka State, India # Department of Civil Engineering, Ladoke Akintola University of Technology, P.M.B 4000, Ogbomoso, Nigeria + Corresponding Author; Email: soojoawo@lautech.edu.ng Abstract One of the crucial factors in sewage management systems is the Design discharge of sewer effluents. This study has applied the principles of System Dynamics (SD) for the modeling of sewer effluents design discharge in NMAM Institute of Technology, Nitte Campus. Rational Formular (RF) and Lloyed Davis Formular (LDF) methods were both employed. The equations were coded in the Visual Basic computer Language and processed using Stella 9.0 software. Input parameters were: population (P), Catchment Area (A), per capita water supply (WS), sewage flow (SF), average annual rainfall (AAR), impermeability coefficient for the area (I), and the time of concentration (t c ). Results showed that the maximum Dry Weather Flow (DWF) in the RF and LDF methods were 111 and 103 litres/sec respectively. The optimum effluents design discharge obtained for the RF and LDF methods were however 637 litres/sec and 617 litres/sec respectively. The DWF/WWF ratio was found as 1:4. The study therefore recommends the use of Rational Formular and combined sewer system for effluents in the study area. Keywords: System Dynamics, Modeling, Sewer Effluents, Design Discharge 1.0 Introduction System Dynamics (SD) is a computer-aided approach to policy analysis and design. It applies to dynamic problems arising in complex social, managerial, economic, or ecological systems [1]. SD is a well- established methodology for studying and managing complex feedback systems, based on system thinking [2]. SD modeling has a wide practical application. It has been used to address various feedback systems, including the environmental management [3], [4], [5], [6], [7], [8], [9], [10]. It requires constructing the