High-rate depth filtration of produced water: Systematic media screening based on performance, backwash and fouling behavior

High-rate depth filtration is a critical tertiary step in produced water (PW) treatment, yet the selection of robust granular media under elevated hydrodynamic stress remains largely empirical and insufficiently systematized. This study introduces a rapid, multi-criteria screening protocol to evaluate the filtration performance, regenerability, and irreversible fouling propensity of eight diverse granular media, including conventional organics, lignocellulosic novel agricultural byproducts, minerals, and repurposed oil-spill sorbents (synthetic sponges). Pilot-scale tests were conducted using synthetic PW (50 mg/L oil) at superficial velocities from 10 to 30 m/h. The results demonstrated that while traditional walnut shell (NS), zeolite (ZM), and diatomaceous earth (DE) sustained consistently high oil removal efficiencies (>95%), whereas the repurposed highly porous spongy media exhibited severe flow channeling and poor performance under dynamic high-shear conditions. For the studied conditions, a generalized kinetic model for backwash oil release was successfully developed through multiple linear regression, revealing that the release of reversibly retained oil follows an intrinsic exponential decay predominantly governed by macroscopic hydrodynamic shear and cumulative oil loading, with limited dependence on media surface chemistry. Conversely, the susceptibility to irreversible fouling was shown to be heavily influenced by macroscopic topography rather than wettability alone. While morphological “pockets” in pecan shell (PS) acted as hydraulic dead-zones hindering oil detachment, the rigid structure of NS and the strong hydration layer of hydrophilic minerals facilitated excellent bed regenerability. By coupling dynamic filtration resilience with generalized oil release kinetics, this study provides a comprehensive predictive framework for optimizing media selection and managing transient oil loads from filter regeneration in industrial facilities.