Economic-Environmental Approach for Optimum Wastewater Utilization in Irrigation: A Case Study in Lebanon

Municipal wastewater of Tyre region, south Lebanon, is currently dumped into the sea without any treatmentcausing significant environmental damage in the area. A sewage treatment project, up to secondary level, in the area isunder planning. This article proposes reusing secondary treated wastewater in crop production in the region. A linearprogramming model is developed to determine the cropping pattern that utilizes all or most of the regions treated effluent,consumes all effluents nitrogen content (being the most limiting constituent), and brings in the highest revenues to theregions farmers. Three scenarios are formulated to test for the optimal cropping pattern under different restrictions andconditions. The first scenario represents optimality under the currently existing cropping pattern, while in the second andthird scenarios new crops are introduced. Supplementary irrigation with fresh water is considered in some sub-scenariosto determine wastewater reuse profitability under this condition. Results reveal that utilization of treated wastewater forirrigation in the region is profitable. The lowest net return is achieved with the current cropping pattern (first scenario).Higher profits are achieved in other scenarios due to introducing new crops to the area. In addition, better results arealways attained once supplementary irrigation is provided.