Removal of tetramethylammonium hydroxide (TMAH) from thin-film transistor liquid crystal display (TFT-LCD) industry wastewater by hydrolysis acidification-aerobic and anaerobic processes

Abstract Tetramethylammonium Hydroxide (TMAH) is widely used as a developer in the thin-film transistor liquid crystal display (TFT-LCD) industry, which is a corrosive alkaline and neuronal toxic compound. In this study, the performances of combined hydrolysis acidification-aerobic and anaerobic batch reactors for synthetic TMAH wastewater treatment were evaluated. It also investigated the real TMAH wastewater treatment in the anaerobic batch reactor. The batch tests focused on the removal efficiencies and intermediate products of TMAH biodegradation during different processes. Furthermore, microbial community structures were identified. The long-term monitoring of 380 days results demonstrated that TMAH degraded can be stably achieved by hydrolysis acidification-aerobic and anaerobic processes, and the total organic carbon removal efficiencies were both higher than 91 %. The pretreatment by hydrolysis acidification process could avoid the inhibition of high concentration TMAH on subsequent aerobic treatment. Main intermediate products during the hydrolysis acidification-aerobic and anaerobic treatments included trimethylamine, dimethylamine, monomethylamine, which can be degraded easily by biotreatment. Consequently, nearly 70 % organic nitrogen in the influent TMAH transferred to ammonium or nitrate, while the mineralization of intermediates caused methane and carbon dioxide generation. The study also proposed TMAH degradation pathways by different processes based on the intermediate’s identification. Analysis of 16s rRNA gene sequencing revealed that mixed microbe contributed in TMAH degradation. At the phylum level, proteobacteria and bacteroidetes were abundant in all the reactors. Besides, patescibateria, cloacimonetes and acidobacteria were dominant in anaerobic reactors as well. This study suggests that traditional combined or single activated sludge processes could be used for TMAH-containing wastewater treatment. Especially, anaerobic process may be favored over other processes.