Effects of short-term irrigation of olive (Olea europaea L. cv. ‘Koroneiki’) trees using treated wastewater contaminated with heavy metals

Several irrigated agricultural perimeters have been established as a part of Tunisian strategy for optimizing the conservation of freshwater and providing alternative water sources. In this work, olive trees were cultivated in a small scale, irrigated with treated wastewater (TWW) from three different industrial wastewater treatment stations and compared with tap water used as a control (GW). In order to evaluate the performance of using effluents characterized by its high metal contents for the irrigation of agricultural crops with high added value, two-year monitoring of soil and plants characteristics was conducted by the evaluation of different physicochemical parameters such as plant growth and soil salts and metal contents. The increase of nutrients such as potassium, nitrogen, phosphorus and sodium was registered in soil after the application of different TWWs compared to the GW. The metal contents in both soil and plants increased but without exceeding the permissible limits. No significant differences in plant growth for all irrigation sources as demonstrated by investigated plant height. The absence of E. coli , Streptococcus and Total coliform in TWWs verified the safe microbial aspect on future olive fruits. Results based on the evaluation of different physicochemical properties of soil, plants growth and characteristics suggest the possibility of a brief reuse of TWWs in the irrigation of the olive tree.