<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">This study was conducted on the Al-Hartha Water Treatment Plant (HWTP), the largest water treatment plant in the city of Basra, during the period from December 2017 to March 2018. This study gives a description of the units and components of the HWTP, and aimed to evaluate the efficiency of the plant by calculating the efficiency of its sedimentation, filtration and sterilisation basins. Additionally, it aimed to examine its water quality by examining the physical and chemical characteristics of the raw water and treated water at this plant and then comparing the findings with the World Health Organisation (WHO) and Iraqi standard limitations.<br /> The results of this study showed that the efficiency of the sedimentation basins is 57%, while the efficiency of the filtration basins is 13.3%, and the sterilisation efficiency ranges from 27 to 50%. The laboratory results for the treated water quality have shown that the turbidity is equal to 12.8 NTU, electrical conductivity (EC) is equal to 7750 &micro;s/cm, the total salt concentration of the total dissolved solids (TDS) is equal to 5200 mg/l, and the concentration of the total suspended solids (TSS) is equal to 65 mg/l of the water outside from the HWTP. All these water quality results are higher than the WHO and Iraqi standard limitations, except the pH value of 6.95, which is within the permissible limits.</span></span></p>