Evaluation of the re-use of treated wastewater for irrigation

Fresh water is considered one of the most important factors in expanding the cultivated area. In arid and semi-arid zones, water resources are scarce. Recently many scientists in different countries have concluded that the re-use of wastewater could help to solve water scarcity problems. An additional target is to protect the environment by reducing the pollution load with little or no risk to the plants, groundwater or human health. Therefore, the principal objective of the present study was to demonstrate the economic aspects of re-using secondary treated wastewater in irrigation, in order to make the best use of existing resources. Thus, field trials were established in a rotation of summer and winter crops during the 2000–2002 seasons to evaluate the effect of irrigation with secondary treated wastewater on the yield and quality of field crops compared with canal water. The present study discusses a part of this study, concerning the effect on the yield and quality of lentils and pearl millet. The experimental treatments for both crops were the same in both growing seasons, involving two water irrigation sources (secondary treated wastewater and canal water) and two fertilization treatments (application of recommended rates of chemical fertilizers and control without fertilizer application). The data demonstrated that crops irrigated with secondary treated wastewater performed equally well or significantly better than those irrigated with canal water. Heavy metal concentrations were very low, and had no influence on crop quality, determined as the chemical composition of lentil seeds and the dry forage yield of millet. Animal performance was also taken into consideration. The results indicated that the seed and biological yields of plants given wastewater in the absence of chemical fertilizers were nearly equal to those of plants given the recommended dose of chemical fertilizers, indicating that wastewater could provide an adequate amount of N, P and K to cover crop requirements at different growth stages.