Hydrodynamic cavitation presents a promising approach to degrading recalcitrant organic pollutants in wastewater, as it generates extreme conditions that promote the formation of reactive oxygen species, particularly hydroxyl radicals. However, cavitation alone typically does not ensure sufficient radical production for effective water treatment, and is, therefore, often coupled with other advanced oxidation processes to enhance free radical yield. Non-equilibrium thermodynamics suggests that chemical reactions in cavitating liquids can be intensified through auxiliary physical effects, such as the relatively unexplored influence of an external magnetic field. This study presents a novel theoretical framework based on phenomenological principles of irreversible thermodynamics and experimentally evaluates the suggested beneficial effect of the synergistic combination of hydrodynamic cavitation and magnetic field. Conducted chemical analyses of treated tap water indicate increased radical activity, particularly reflected in shifts in pH and oxidation-reduction potential. The study highlights the potential of integrating magnetic fields into advanced oxidation processes and demonstrates the value of non-equilibrium thermodynamics concepts in understanding and optimizing such processes.