Comprehensive analysis and characterization of overhaul wastewater from petrochemical refineries

During the overhaul of petrochemical refineries, a large amount of wastewater will be discharged unorganized, which has a serious impact on the operation of wastewater treatment system. In this study, macroscopic pollutant index analysis was combined with microscopic pollutant composition analysis, and the water quality of cleaning wastewater and cleaning-passivation wastewater were characterized from four aspects: pollutant load, system stability, pollutant composition, and biological toxicity. Both cleaning wastewater and cleaning-passivation wastewater exhibited high organic pollutant loads, high concentrations of suspended and colloidal pollutants, high system stability, and strong acute biological toxicity. The composition of polar pollutants of cleaning wastewater and cleaning-passivation wastewater was dominated by OxS1. Cleaning wastewater had the highest relative abundance of O3S1, which was speculated to be derived from alkyl benzene sulfonates. The relative abundance of O4S1 was the highest in cleaning-passivation wastewater, which was presumed to come from alkyl sulfates or sulfate surfactants. There was a significant difference in the composition of weakly polar pollutants between the cleaning wastewater and cleaning-passivation wastewater. Cleaning wastewater was mainly consisted of alcohol ethers, ethers, and petroleum hydrocarbons. Cleaning-passivation wastewater was mainly consisted of small molecule heterocycles, aromatic hydrocarbons, and phenols. The results could guide the development of pretreatment processes for overhaul wastewater, and provide support for the stable operation of comprehensive wastewater plant during overhaul of petrochemical refineries.