Development of methodology for the optimal operation of soil aquifer treatment systems

Soil aquifer treatment (SAT) systems are used for reclamation of sewage effluent by groundwater recharge. Increasing demand on water supplies has stimulated the production or planning of many SAT systems that will use reclaimed wastewater for groundwater recharge. These systems are comprised of a series of filtration basins. The design and operation of soil aquifer treatment systems presently relies primarily upon dgment and experience. This research effort is developing a methodology for determining the optimal peration of SAT systems that is based upon mathematically describing the problem as a discrete-time ptimal control problem. The resulting mathematical problem is a large-scale nonlinear programming problem. Solution of the problem is being accomplished by interfacing a nonlinear programming optimizer, which is solved by a differential dynamic programming algorithm, with a simulator that describes the filtration process, unsaturated flow, effects of surface clogging and biological clogging, biological removal of nitrogen and organics. Major efforts are devoted to numerical performance of the optimization model elution, and development of the simulator. Initial results of interfacing the optimizer with the simulator without water quality concern show high convergence rate. The operation pattern determined by this method reasonable. This new methodology will be a tool for engineers to evaluate choices regarding the potential of the design and operation of SAT systems.