Optimization of Desalination Location Problem Using MILP A. M. Emhamed and B. Czuczai Dept. of Chemical Engineering, Budapest University of Technology and Economics, H-1111, Budapest, Muegyetem rkp. 3, Hungary L. Horvath Research Laboratory of Material and Environmental Sciences, Chemical Research Center of HAS, H-1525 Budapest, Hungary E. Rev and Z. Lelkes Dept. of Chemical Engineering, Budapest University of Technology and Economics, H-1111, Budapest, Muegyetem rkp. 3, Hungary DOI 10.1002/aic.11255 Published online July 31, 2007 in Wiley InterScience (www.interscience.wiley.com). A new mixed-integer linear programming model for location problem is developed in this work in order to find the optimal co-ordinates of the desalination plants. The model takes into account the given locations and capacities of the water incomes, the demands, and the costs of plants and pipelining. Feasible and infeasible plant regions are distinguished for locating the plants. The model has been developed in two consec- utive phases. First, a basic model is developed that provides a solution within short time but does not take into account the possibility of pipeline branching. Application of this model gives rise to redundant pipelines to some connections, involving extra costs. Pipeline branching is dealt with an improved model developed in the second phase. This improved model provides realistic solution but with much longer computa- tion time. The results of applying the different models on motivated examples of differ- ent sizes are detailed. Ó 2007 American Institute of Chemical Engineers AIChE J, 53: 2367– 2383, 2007 Keywords: location, distance, pipeline, feasible region, MILP Introduction A shortage of potable water in many populated areas around the world where 2 billion people go without fresh water on a daily basis has already reached the point at which supply of seawater is the only solution. Seawater, however, must be desalinated before use. Desali- nation is a process that removes minerals (not limited to salt) from seawater, brackish water, or treated waste water. The best known desalination processes are multi-stage flash, multi-effect distillation, vapor compression, solar distillation (SD), reverse osmosis (RO), and electrodialysis. RO and SD are considered in this work. In RO, feed water is pumped at high pressure through permeable membranes, separating salts from the water. The quality of the produced water depends on the applied pressure, the concentration of salts in the feed water, and the salt permeation constant of the membranes. 1 SD is a clean and environmentally safe technology for fresh water production. The simplest and most practical solar still is of a single-basin type, which consists of a box with a tilted Correspondence concerning this article should be addressed to Z. Lelkes at lelkes@mail.bme.hu. Ó 2007 American Institute of Chemical Engineers AIChE Journal September 2007 Vol. 53, No. 9 2367