Assessment of hybrid treatment process for high-COD oily wastewater following Iraqi discharge regulations: a case study from Baghdad power plant

In this work, samples of oily wastewater were collected at different time intervals from a gas power plant in Baghdad, Iraq. The samples were subjected to laboratory analyses to identify the types and concentrations of pollutants before and after being subjected to a series of treatment stages. The proposed treatment system consists of two stages. The first is Dissolved Air Flotation (DAF), followed by sand filtration, then by microfiltration. This stage was found to effectively remove a significant portion of oils and suspended solids, bringing the concentration of oil and grease within the permissible limits. However, the COD concentration remains in the range of 180-200 mg/L, which exceeds the allowable limit of 100 mg/L according to these standards. This indicates that this stage alone does not fully meet the Iraqi specifications. The second stage involves treatment through an advanced oxidation process, followed by biological treatment. Together, these two stages can fully satisfy all Iraqi standards. This investigation successfully identified the optimal technological treatment pathway that reduced 98% of oil and grease with 95% of COD contents.