optimum design of sewer collection networks

various methods have been used to economically design wastewater and stormwater collection systems. in this article, discrete differential dynamic programming (dddp) which is a subsection of dynamic programming (dp) was used. for each pipe network, various alternatives such as depth and slope of pipe laying and various diameters could be considered to satisfy hydraulic and engineering constraints. from an economic viewpoint, however there are few alternatives to minimize the costs. planning algorithm for dddp is based on determination of one initial answer for network and modifying the answers in continous trials which satisfy economic and engineering considerations. to limit the range of answers in each trial, a corridor of solutions was defined. this range in each trial will converge to an optimum solution. in this regard, a computer program called snop (sewer network optimization) has been developed. several design examples have been run with this program. the results show the suitability of the program.