Turbidity is a visual property of water that expresses the amount of suspended substances in the water. Its presence in quantities more significant than the permissible limit makes the water undrinkable and reduces the effectiveness of disinfectants in treating pathogens. On this basis, turbidity is used as a basic indicator for measuring water quality. This study aims to evaluate the removal efficiency of AL- Muthanna WTP. Water turbidity was used as a basic parameter in the evaluation, using performance improvement evaluation and data from previous years (2016 to 2020). The average raw water turbidity was 26.7 NTU, with a minimum of 14 NTU, with a maximum of 48 NTU. Water turbidity value for 95% of settling daily reading data was (13.7) NTU which is larger than the goal value (10) NTU, which achieves (51.2) % of the optimum goal. In comparison, the water turbidity value for 95% of daily reading data of water filtered was (6.90) NTU which is larger than the goal value (5) NTU, which achieves (68.8) % of the optimum goal. The removal efficiency for previous years (2016 to 2020) was (78.5, 76, 73.5, 72, 68)%, respectively, within acceptable limits.

The water quality index is the most common mathematical way of monitoring water characteristics due to the reasons for the water parameters to identify the type of water and the validity of its use, whether for drinking, agricultural, or industrial purposes. The water arithmetic indicator method was used to evaluate the drinking water of the Al-Muthana project, where the design capacity was (40000) m3/day, and it consists of traditional units used to treat raw water. Based on the water parameters (Turb, TDS, TH, SO4, NO2, NO3, Cl, Mg, and Ca), the evaluation results were that the quality of drinking water is within the second category of the requirements of the WHO (86.658%) and the first category of the standard has not been met due to defects in design and operation and the inlet and outlet values of dissolved minerals were very close due to the absence of soluble salt removal units in AL-Muthana project