Optimization design method for urban sewage collection pipe networks.

In this study, a secondary subsystem mathematical model is established under the condition that the layout of the sewage collection branch, trunk, and main pipe network projects is fixed. The sewage collection branch and trunk pipe network projects are treated as the research objective by taking the minimum annual cost of the sewage collection pipe network projects as the objective function, the longitudinal slope of the pipe section and the economic flow rate of the pipe section as constraints, and the diameter of the pipe section as the decision variable. A first-level subsystem mathematical model is established by taking the sewage collection branch, trunk, and main pipe network project as the research object. A large system mathematical model is established in the same manner. This model can be solved using the large system secondary decomposition-dynamic programming aggregation method, and the optimal diameter for each pipe section can be obtained. A regional sewage collection pipe network project in Taizhou city was considered as an example for comparative analysis before and after optimization, and the results verified that the optimization method proposed in this study can solve this complex large system optimization problem.