Trickling filter process is focused on developing Asian countries in recent years as an alternative energy-saving wastewater treatment to conventional activated sludge systems. This paper investigated influential hydraulic operational parameters on the process performance using a nitrification reactor. The trickling filter process was expressed as 2-dimensional biofilm layers where the influent flowed to the bottom of the filter bed while oxygen was dissolved from the ambient air. The 4 m-height pilot-scale trickling filter filled with tubular plastic media (1.5 cm × 1.5 cm, 371 m²/m³-reactor volume) was installed at a municipal wastewater treatment plant in Da Nang, Vietnam. During the 2-day hydraulic stress test, the nitrogen and hydraulic loadings were changed in a step-wise manner. Focusing on the nitrification which was a dominant oxygen uptake, the process performance was dynamically simulated with a modification of IWA Activated Sludge Model (International Water Association). The effluent concentrations of dissolved oxygen and inorganic soluble nitrogenous compounds were reasonably calculated under the hydraulic loading ranging between 2.4 and 18 m/h. The reactive wetted surface area of the filter seemed to increase when high linear velocity of the fluid was applied, which resulted in the increase of volumetric biological reaction rates.