Abstract: This paper established a mathematical model to find the optimal wastewater treatment station construction scheme,  which could save enterprise's wastewater treatment station cost. It is very important for the enterprises to build wastewater treatment stations. The optimal solution obtained by stochastic enumerative method is the global optimum. The model input variables are simple. In theory,  to obtain the optimal siting program only needs to know the emissions of the wastewater plants and location coordinates.This paper applied the model to simulate calculating two arbitrary structure construction schemes for some factories' wastewater treatment stations,  which tested the rationality and validity of the model.

Key words: Bell number, matrix of directed graph;stochastic exhaustive traversal algorithm, deviation rate