The aim of this work was to evaluate the effect of treated wastewater short and long-term irrigation on essential oil composition from E. camaldulensis Dehn in order to detect allelopathic impacts on seed germination and seedling growth of Amaranthus hybridus L, Chenopodium album L, Echinochloa crus-galli (L) Beauv and Lolium perenne L as important weeds on many crops.