Baghdad city has been faced numerous issues related to freshwater environment deteriorations due to many reasons, mainly was the discharge of wastewater without adequate treatment. Al-Rustamiya Wastewater Treatment Plant (WWTP) have been constructed among many plants in Baghdad city to reduce the amount of wastewater discharged into natural environment and its subsequent adverse effects. This study was conducted to evaluate the performance of the plant which consist of a conventional activated sludge (CAS) and sequencing batch reactors (SBR) systems as secondary treatment units and its ability to meet Iraqi specifications. A reliability level determination and analysis also were conducted to find the plant's stability and its capability to produce effluents that met the local standards. Coefficient of Reliability (COR) determination was done for effluent's concentrations of BOD5, COD, and TSS obtained from Al-Rustamiya WWTP for two years' data operation (2015-2016), using Iraqi standards concentrations. Generally, the results showed the effectiveness of Al-Rustamiya WWTP-(CAS and SBR system) was a major concern due to inadequate sewage treatment and that the plant effluents of both systems selected parameters BOD5, COD and TSS are not meeting the Iraqi standards due to many problems mainly were operational problems result in overall poor performance.
