Sustainability in wastewater treatment can encourage the processes of planning, maintenance, design, operation, and management of wastewater infrastructure in a manner that minimizes the consumption of depletable resources and reduce the impacts and damages caused by them on the environment. Life cycle assessment (LCA) is an appropriate methodological framework for evaluating the sustainability of wastewater treatment systems. The present study used the Simapro7 program that is based on the basics of LCA, it was used for impact and damage analyzing Najaf Waste Water Treatment Plant WWTP. LCA results proved Najaf WWTP has a significant environmental impact and damage equal to 120 point / 1m3 wastewater, The potential reasons behind environmental impacts were ( non-renewable energy, respiratory inorganics, and global warming). The most affected phase was the construction phase rather than operation.