Use of the desalted wastewater for lettuce (Lactuca sativa L.) production in NFT hydroponic system

The desalination process by reverse osmosis was used for the treatment of brackish water, making possible the usage human consume in semiarid zones. This process has a limiting factor: it produces wastewater with high salinity. To evaluate the effect of the use of desalted water on lettuce (Lactuca sativa L.) production cv. Vera in a NFT hydroponics system an experiment was carried out in a greenhouse located at the Departament of Environmental Sciences of the Universidade Federal Rural do Semi-Arido, in a statistical test with completely randomized blocks with four repetitions and six treatments. The salinity level of the war between treatments was checked with and without dilution of the wastewater, adding the nutrient solution with salinity of 1 dS m(-1) (100% public water supply - 1.4 dS m(-1); 85% water supply and 15% wastewater - 1.9 dS m(-1); 75 % wastewater + 25 % water supply - 2.7 dS m(-1); 50% wastewater e 50% water supply - 3.8 dS m(-1); 25 % wastewater and 75 % water supply - 4.9 dS m(-1) and wastewater gathered from desalter - 5.5 dS m(-1). The number of leaves, diameter of the stem, fresh and matter biomass and leaf area were analyzed. All the analyzed variables were negatively influenced in a linear way by the effect of the concentration of salts in irrigation water. Biomass and leaf area are more sensitive to saline stress in the cultivar studied, and fresh matter production was reduced by 94.83%, when CEa was increased from 1.4 to 5.5 dS m(-1).