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Tetramethylammonium hydroxide (TMAH) is widely used as a developer and etchant in the thin-film transistor liquid crystal display industry, which is the main component of developer wastewater with low C/N ratio. This study investigated TMAH degradation by combined anaerobic/integrated fixed film activated sludge (A/IFAS) process, especially for nitrogen removal. Effects of process condition on the TMAH degradation were studied, including dissolved oxygen concentration in IFAS reactor and the temperature of anaerobic reactor. Especially, the nitrogen removal was studied through the monitoring of intermediate products during TMAH biodegradation. The results indicated that lower the anaerobic treatment temperature can provide more available organic matters to enhance the denitrification in the subsequent IFAS reactor. Less oxygen supply in the IFAS reactor contributed to simultaneous nitrification and denitrification. Removal efficiency of total organic carbon and total nitrogen was up to 95.8% and 80.7%, when the temperature of anaerobic treatment was controlled at 30 °C with the DO kept at 0.7 mg/L. It indicated that A/IFAS process was efficient in carbon and nitrogen removal for TMAH degradation. The results also confirmed intermediate products of TMAH biodegradation can be used as the electron donor during denitrification, including trimethylamine, dimethylamine and methylamine. Illumina MiSeq sequencing showed that Proteobacteria was the dominant phylum contribute to nitrogen removal. Compared to sludge flocs in IFAS reactor, richer community and higher microbial diversity were observed in the biofilm. [Display omitted] • Anaerobic/IFAS process was established for TMAH degradation. • Low anaerobic temperature and DO enhanced nitrogen removal. • TMAH degradation intermediates were more accessible for denitrification. • Biofilm had richer community and higher microbial diversity than sludge floc in IFAS. [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]