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BACKGROUND Psychoactive pharmaceuticals used to treat neurological disorders are of great concern because of their frequent detection in the aquatic environment and drinking water. The possibility for concurrent formation of N‐nitrosodimethylamine (NDMA) from psychoactive pharmaceuticals during disinfection is still not well‐studied. In the present study, seven widely used psychoactive drugs were selected due to their possession of a DMA functional group. The NDMA formation potentials of the selected drugs were assessed during free chlorine (NaOCl) and chlorine dioxide (ClO2) disinfection processes. The influence of several parameters (i.e. disinfectant dose, pH and water matrix) was investigated to better understand the reaction between the drugs and disinfectants that cause the formation of NDMA. RESULTS: The NDMA molar yields of seven pharmaceuticals were higher than 2%. NDMA formation was independent of the pH value, and more NDMA formation was observed during free chlorine chlorination. NDMA generation was enhanced when the selected pharmaceuticals were present in real water matrices, especially in secondary effluent. CONCLUSION: This study demonstrated that the seven selected psychoactive pharmaceuticals containing dimethylamine groups can serve as NDMA precursors during free chlorine and chlorine dioxide chlorination processes. ClO2 was a proper disinfectant for controlling NDMA formation during chlorination. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Venlafaxine, a representative antidepressant, has been detected frequently in aquatic environments. The treatment of venlafaxine by free chlorine (NaOCl) and chlorine dioxide (ClO 2) was investigated in this study. The effects of operational variables and the water matrix on venlafaxine degradation were evaluated. The transformation pathways of venlafaxine were also studied. The results indicated that venlafaxine was removed efficiently during disinfection processes, especially when reacted with ClO 2. A higher dosage of disinfectant and mildly alkaline conditions (pH 9) enhanced the degradation of venlafaxine. The reactions were impacted when the tests were conducted in real water matrices, especially in secondary effluent. The presence of chloride and low concentrations of fulvic acid enhanced venlafaxine decomposition. The presence of Br− also accelerated the reaction between venlafaxine and NaOCl. However, NO 2 − inhibited venlafaxine removal in both disinfection processes. Six intermediates were identified during venlafaxine degradation by ultrahigh-performance liquid chromatography with quadrupole-time-of-flight mass spectrometry, and the main reactions included dehydration and demethylation. [Display omitted] • Venlafaxine was removed efficiently both by NaOCl and ClO 2. • Venlafaxine chlorination fits pseudo-first-order reaction kinetic. • Low concentration of fulvic acid and Cl− improved venlafaxine removal. • Main reaction mechanism included dehydration and demethylation. • ClO 2 is a proper disinfectant for venlafaxine decomposing. [ABSTRACT FROM AUTHOR]

The highly prescribed antidepressant, citalopram, as one of newly emerging pollutants, has been frequently detected in the aquatic environment. Citalopram oxidation was examined during sodium hypochlorite (NaOCl) and chlorine dioxide (ClO2) chlorination processes since conventional wastewater treatment plants cannot remove citalopram effectively. Citalopram has been demonstrated to form N-nitrosodimethylamine (NDMA) during chlorination in our previous study. Further investigation on NDMA formation kinetics was conducted in the present study. Influences of operational variables (disinfectant dose, pH value) and water matrix on citalopram degradation, as well as NDMA generation, were evaluated. The results indicated high reactivity of citalopram with NaOCl and ClO2. NDMA formation included two stages during CIT oxidation, which were linear related with reaction time. NaOCl was more beneficial to remove CIT, but it caused more NDMA formation. Increasing disinfectant dosage promoted citalopram removal and NDMA formation. However, no consistent correlation was found between citalopram removal and pH. Contrary to the situation of citalopram removal, NDMA generation was enhanced when citalopram was present in actual water matrices, especially in secondary effluent. DMA, as an intermediate of citalopram chlorination, contributed to NDMA formation, but not the only way. [ABSTRACT FROM AUTHOR]