Background: The determination of influent and effluent water quality of water treatment plants is important to increase standards of water quality for users. Parsabad city situated in north of Ardabil province and is the biggest city of province Ardabil. So, this study was accomplished due to lack of substantial studies for Parsabad water treatment plant. In the study, some of the important parameters of water was investigated for 7 years and was presented solutions for improvement treatment plant performance.

Methods: This study was accomplished since 1384 to 1390 and four parameters total dissolved solids, turbidity, phosphate and calcium with 192 samples (96 samples collected from treatment plant influent and 96 samples collected from effluent) were analyzed according to standard methods for the examination of water and wastewater.

Results: Maximum removal performance of turbidity, total dissolved solids, phosphate and calcium were 99.8, 6.1, 92.67 and 28.45 respectively, during 7 years operation of treatment plant.

Conclusions: The results of this study showed that Parsabad water treatment plant with having a rapid sand filter, enable to remove turbidity up 85% when maximum turbidity at treatment plant influent was 700 NTU. But, significant difference statistically was not observed between influent and effluent samples of total dissolved solids and calcium (P_value˃0.05) and removal performance were trivial for total dissolved solids and calcium. Also, this treatment plant has not good performance (mean %38) for phosphate removal.