Problem: Sudan is currently facing a serious problem of disposal and reuse of waste water from different sources. In the oil industry, refinery waste water was estimated to be 20 million m 3 /annum. Evaporation ponds were established in order to treat the waste water for further use, mainly irrigating trees as shelter belts and wind breaks around the refinery area. Objective:The ongoing tree planting efforts, using the refinery waste water for irrigation, seemed to be based on inadequate information regarding the use of the most suitable tree species in terms of both site adaptability and tolerance to the waste water quality. In addition, there were hazardous effects of waste water on the environment, mainly on soil characteristics.Methodology: Six tree species (Acacia tortili, Eucalyptus camadulensis, Azadrichta indica, Grewia tennax, Eugenia jambolana, and Conocarpus erectus) were selected and used in a completely randomized block design in a field trial using refinery waste water for irrigation. Data were collected concerning plant growth parameters and performance throughout the experimentation period of 15 months. Soil samples were analysed after the application of waste water for quality assessment. Findings:The results of the experiment revealed a significant difference between all six tree species in their tolerance to waste water. These differences included number of leaves, number of branches, plant height and stem diameter. The most suitable tree species found were Conocarpus erecta and Acacia tortilis, while the least tolerant tree was Grewia tenax. Soil analysis results revealed a remarkable change in some soil characteristics after waste water application, mainly electric conductivity, pH and minerals concentrations.Value: Refinery waste water could be used for irrigation purposes, but only under certain circumstances. Proper treatment measures should be introduced before the use of waste water. Soil quality was also important and certain precautions should be implemented before irrigation.

Sudan is currently facing a serious problem of disposal and reuse of waste water from different sources. In the oil industry, re nery waste water was estimated to be 20 million m 3 /annum. Evaporation ponds were established in order to treat the waste water for further use, mainly irrigating trees as shelter belts and wind breaks around the re nery area.