OPTIMAL DESIGN OF TRUNK SEWER

Abstract

The cost of a sewage collection network constitutes a major fraction of the overall cost of wastewater disposal. In the context of maximizing service to the population with the available functional resources, it is essential that wastewater engineers should take recourse to optimal designs. Substantial sums of money can be saved through decomposing sewer network into a set of sewer lines and optimizing each separately. The dissertation work presented herein addresses itself to the development of a computer based mathematical program for optimal design of trunk sewer. As it is practically impossible to select the best from all feasible design alternatives, a computer based mathematical programming technique in identifying optimal solution is essential. The problem consists of minimization of a nonlinear cost function subjected to nonlinear constraints, and is solved using Lagrange-multiplier method. The program developed selects the optimal depth-diameter combination for each link of the sewer line while satisfying all the constraints. The sewer line has also been designed as per Central Public Health and Environmental Engineering Organisation (CPHEEO) manual (1993) and finally the results are compared with the optimal solution for south Moradabad city.