Effects of influent organic load on TMAH (tetramethylammonium hydroxide) wastewater treatment by anaerobic process

Abstract

Tetramethylammonium hydroxide (TMAH) is a corrosive alkaline and neuronal toxic compound, which is widely used in the thin-film transistor liquid crystal display industry. In this study the performance of the anaerobic sequencing batch reactors (SBR) for treating synthetic TMAH wastewater under different organic influent loads was evaluated thoroughly over a 208 day period. The results indicated that when the influent organic load was below 376.4 mg TOC/(L·day), total organic carbon (TOC) removal was enhanced with influent organic load increasing. And the maximum TOC removal efficiency and CH4 production reached 92.5% and 589 mL/L reactor of one cycle, respectively. Further raising the load suppressed the TMAH degradation and microbiological activity. Only 6.0% organic nitrogen converted to ammonium and TOC removal efficiency declined to 13.5% at the influent organic load of 1130.5 mg TOC/ (L·day), with anaerobic sludge settling performance decline. And the biogas production of one cycle dropped to 60 mL/L reactor. It was also found that reducing influent organic load could not restore the system. Microbial diversity and richness also varied in response to the influent organic load. Illumina MiSeq sequencing analysis indicated Caldisericum, norank_f_KD1–131, norank_f_Bacteroidetes_vadinHA17, and Treponema were enriched at the influent load of 376.4 mg TOC/(L·day). RT-qPCR results confirmed that high influent organic load suppressed the expression of the ureC gene and mcrA gene, and then inhibited ammonification and methanogenesis.