Optimization of Drainage Design Parameters with the Aim of Reducing Environmental Damage in Steady-State C onditions

Diameter, insertion depth and spacing of drainage pipes are three crucial variables in the design of underground drainage network. Effluents have a great potential to leave lots of damage on the environment. The proper selection of design variables can lead to reducing the environmental damage. The purpose of this paper is to provide a model for selecting optimal design parameters for underground drainage systems to reduce environmental damage, in a way that after the discharge of drainage to the river, river salinity concentration does not exceed the acceptable limit.

For this purpose, maximization of difference between drainage water salinity and acceptable limit was considered as the objective function. Genetic Algorithm (GA), kind of evolutionary algorithm, has been used to simulate the transmission and the salt Hooghoudt model was used also. In Hooghoudt model water transition to drainage is modeled in two upper and lower individual part. In order to evaluate the proposed model, an agro-industrial unit Salman Farsi was chosen as case study. Matlab software was employed to program the formula and algorithm which has been used in this research, including Hooghoudt salinity transfer simulation function and GA algorithm optimization.

Results show that the pipe depth is complying with minimum allowable depth. In other words, since the objective function of the model is to achieve minimal environmental damage, the minimum depth of installation is generally chosen. Optimum diameter, insertion depth and spacing have been obtained 1.3, 0.1 and 34.3 respectively. The results of the sensitivity of the model to change of the two basic assumptions, minimum allowable depth and stabilize the water table depth stabilizing, shows by increasing the allowable minimum depth of installation, drainage spacing increases and reducing the depth of the water table stabilizing will increase the drainage intervals and leads to increasing the concentration of drainage water discharged to the environment.
Discussion and

In this study and by using information about the Salman Farsi agro-industry company, to reduce the environmental damage caused by drainage projects, installation depth of drainage should be equal to the minimum allowable depth.