This study investigated the removal of 15 trace organic chemicals (TOrCs) occurring at ambient concentrations from municipal wastewater treatment plant effluent by advanced oxidation using UV/H2O2 at pilot-scale. Pseudo first-order rate constants (kobs) for photolytic as well as combined oxidative and photolytic degradation observed at pilot-scale were validated with results from a bench-scale collimated beam device. No significant difference was determined between pilot- and lab-scale performance. During continuous pilot-scale operation at constant UV fluence of 800 mJ/cm2 and H2O2 dosage of 10 mg/L, the removal of various TOrCs was investigated. The average observed removal for photo-susceptible (kUV>10−3 cm2/mJ; like diclofenac, iopromide and sulfamethoxazole), moderately photo-susceptible (10−4<kUV<10−3 cm2/mJ; like climbazole, tramadol, sotalol, citalopram, benzotriazole, venlafaxine and metoprolol), and most photo-resistant (kUV<10−4 cm2/mJ; like primidone, carbamazepine and gabapentin) compounds was 90%, 49% and 37% including outliers, respectively. The poorly reactive compound TCEP was not significantly eliminated during pilot-scale experiments. Additionally, based on removal kinetics of photo-resistant TOrCs, continuous pilot-scale operation revealed high variations of OH-radical exposure determined from removal kinetics of photo-resistant TOrCs, primarily due to nitrite concentration fluctuations in the feed water. Furthermore, a correlation between OH-radical exposure and scavenging capacity could be determined and verified by mechanistic modeling using UV fluence, H2O2 dosage, and standard water quality parameters (i.e., DOC, NO3−, NO2− and HCO3−) as model input data. This correlation revealed the possibility of OH-radical exposure prediction by water matrix parameters and proved its applicability for pilot-scale operations. Display omitted •Comparison of UV/H2O2 efficiency at pilot- and laboratory scale.•Removal assessment of 15 trace organic chemicals (TOrCs).•Ambient TOrC concentrations in municipal wastewater effluent (no spiking).•Scavenger capacity is dominated by nitrite concentration fluctuations.•Mechanistic modeling of OH-radical exposure by water matrix and process parameters.