Tetramethylammonium hydroxide (TiVIAH) is an alkaline, neuronal toxic, and chemically stable compound; furthermore, it is widely used in the high-tech industry as a developing agent. Disposal of TMAH wastewater from an industrial plant is a difficult and costly problem. Ultraviolet light (UV) activated persulfate (S2O82-) is an advanced oxidation process proven to be effective in destroying a variety of organic pollutants. This bench-scale study investigated the feasibility of using the UV/S2O82- process to treat TMAH. The effects of various operational parameters, including pH conditions, dosages of persulfate, UV intensities, and system temperatures were evaluated. The results revealed that pH 2 exhibited higher decay rate of TMAH (kobs = 0.0331 0.0031 min(-1)) than other pH conditions (pH 7 and 11) at 20 degrees C. In general, the TMAH decay increased with increasing persulfate dosage; however, the highest TMAH degradation rate was observed with a persulfate concentration of 50 mM. Also, higher reaction temperature and stronger UV irradiation can increase the degradation of TMAH. TMAH degradation byproducts were identified and finally transformed to nitrate and ammonium, which suggested that the demethylation mechanism was the main degradation pathway. (C) 2014 Elsevier B.V. All rights reserved.