Innovative Treatment Approach for Oil Refinery Effluent Using Integrated Activated Sludge and Mn/Cu/Ni‐Layered Double Hydroxide/Magnetite Nanocomposite

Petroleum oil refining industry generates complex wastewaters with toxic substances (hydrocarbons, phenols, ammonia, nitrogen, sulfur compounds, and heavy metals), posing significant environmental threats to aquatic ecosystems and groundwater. To address this, and overcome limitations of the traditional treatment methods, an innovative treatment system was developed by integrating Mn/Cu/Ni-layered double hydroxide (LDH)/magnetite (Fe₃O₄) nanocomposite (NC) into a traditional activated sludge (AS) process to enhance the performance. To the best of our knowledge, this magnetic nano-trimetal combination is investigated for the first time as an innovative alternative for the treatment of oil refinery effluents. Petroleum refinery effluent (PRE) from Alexandria, Egypt, where traditional AS treatment is adopted, was treated using two bench-scale AS basins, modified with the synthesized and characterized NC. Four trials were conducted-three in sequential batch mode and one in continuous mode. The integrated system (Trial 3) significantly enhanced contaminants removal within 45-135 min, achieving 89.0 ± 0.36%, 91.5 ± 0.44%, 87.6 ± 0.84%, and 66.87 ± 0.57% removal of total suspended solids (TSS), chemical oxygen demand (COD), oil and grease (OG), and ammonia, compared to much lower rates achieved by the unmodified AS system (Trial 2). A separate NC filter system (Trial 4) could achieve rapid removal within 2-6 min, with 83.6%, 89.8%, 87.6%, and 64.8% removal for TSS, COD, OG, and ammonia, respectively, and also improved TDS control. These findings confirm and highlight that the integrated LDH/Fe₃O₄ NC-AS system is a highly efficient, rapid, and cost-effective approach for treating refinery effluents, with the potential to meet discharge limits and enable water reuse in industrial applications.