Economic-environmental approach for optimum wastewater utilization in irrigation: A case study in Lebanon

Municipal wastewater of Tyre region, south Lebanon, is currently dumped int o the sea without any treatment causing significant environmental damage in the area. A savage treatment project, up to secondary level, in the area i s under planning. This article proposes reusing secondary treated wastewate r in crop production in the region. A linear programming model is developed to determine the cropping pattern that utilizes all or most of the region' s treated effluent, consumes all effluent's nitrogen content (being the mos t limiting constituent), and brings in the highest revenues to the region's farmers. Three scenarios are formulated to test for the optimal cropping p attern under different restrictions and conditions. The first scenario repr esents optimality under the currently existing cropping pattern, while in t he second and third scenarios new crops are introduced. Supplementary irrig ation with fresh water is considered in some sub-scenarios to determine was tewater reuse profitability under this condition. Results reveal that utili zation of treated wastewater for irrigation in the region is profitable. Th e lowest net return is achieved with the current cropping pattern (first sc enario). Higher profits are achieved in other scenarios due to introducing new crops to the area. In addition, better results are always attained once supplementary irrigation is provided.