This study investigates hydrodynamic parameters governing pollutant degradation in a low-temperature plasma (LTP) reactor utilizing porous alumina ceramic media. A validated 3D Volume of Fluid (VOF) model simulated air–water two-phase flow to resolve film thickness, wettability, wetting area, residence time, and liquid hold-up across varying flow rates. Experimental measurements confirmed the CFD predictions and showed that increasing the flow rate led to a sharp decline in degradation efficiency due to reduced residence time and increased film thickness. Notably, maximum degradation (∼33.4 mg/L) occurred at intermediate flow conditions (Q ≈ 7.0 L/h, RT ≈ 6.1 s), whereas degradation stagnated at higher flow rates due to shortened treatment time and possible side reactions indicated by conductivity shifts. Kinetic analysis of the experimental data confirmed a zero-order degradation mechanism, with a strong linear correlation between residence time and indigo carmine removal (R² = 0.997). Regression and desirability-based optimisation identified 10.97 L/h as the ideal flowrate, balancing surface wetting and residence time for effective degradation (∼31.2 mg/L). Sensitivity analysis confirmed that film thickness and residence time were the most influential factors. The study offers a quantitative framework for optimising LTP reactors by integrating CFD, experiments, and multi-criteria optimisation.