Biological treatment of electronic industry wastewater containing TMAH, MEA and sulfate in an UASB reactor

Abstract

This study investigated the feasibility of the methanogenic treatment of electronic industry wastewater containing tetramethylammonium hydroxide (TMAH), monoethanolamine (MEA) and sulfate in a lab-scale mesophilic up-flow anaerobic sludge blanket reactor. Feeding a mixture of electronic industry wastewater and co-substrate organics to the reactor for smooth acclimatization of sludge gave complete degradation of each organics within five days. When the reactor was fed only electronic industry wastewater, total COD removal, TMAH removal and MEA removal were achieved over 80, 99 and 99%, respectively, at an organic loading rate of 11.5 kg-COD m⁻³day⁻¹. 173 mg-S L⁻¹ of influent sulfate was almost reduced simultaneously with the COD removal. In order to evaluate performance stability, the TMAH shock load event was performed under the conditions of 11,000 mg-COD L⁻¹ for 24 h. Inflow of high TMAH concentration inhibited TMAH degradation and sulfate reduction for more than one month, however, not MEA. The batch feeding experiment and specific activity measurement revealed degradation pathways of each organics. TMAH was degraded via methanogenic pathway without sulfate reduction, MEA was degraded via methanogenic pathway with sulfate reduction. The results indicated that methanogenic treatment was applicable to electronic industry wastewater by appropriate reactor handling.

Keywords:

• Tetramethylammonium hydroxide
• monoethanolamine
• anaerobic treatment
• sulfate reduction
• degradation pathway
• inhibition concentration of TMAH

Acknowledgment

We express our gratitude to Mutsumi Kimura and Kanna Kawaguchi for their experimental support.

Additional information

Funding

This study was partially supported by Yashima Environment Technology Foundation, Grant-in-Aid for for Scientific Research (C), 18K11742 of JSPS KAKENHI(C) and Nagaoka University of Technology grant for collaborative research with National Institute of Technology. Also, part of this study was supported by “project to develop water quality improvement and assessment methods for aquatic environment conservation” of National Institute for Environment Studies.