Metabolite Identification and Disinfection By-product Formation in AAO-MBR System with Waste Liquid Isopropyl Alcohol as a Carbon Source

Abstract

Carbon sources as a substrate can provide organic matter for denitrification and nitrification, facilitating the removal of pollutants. However, low-cost and efficient alternative carbon sources are an urgent problem to be solved for wastewater treatment processes globally. Isopropyl alcohol (IPA), as a waste liquid produced during the cleaning process in the electronics industry, can serve as the carbon source for microbial growth. Herein, the influence of conventional carbon sources (glucose-coupled sodium acetate) and IPA carbon source on denitrification performance, metabolite identification, microbial community composition, and disinfection by-product (DBP) formation was assessed by a denitrification system (AAO-MBR). Results showed that the nitrogen removal efficiency of IPA as a carbon source (69.2%) was similar to that of conventional carbon sources (72.6%). Notably, the results of the metabolites of the two carbon source effluents showed that CHO and CHNO compound classes were the most abundant species in terms of quantity, and lignin (59.5-60.1%) was the main component in two carbon source effluents. Additionally, the diversity of microbial communities at the genus level was significantly different, but organic matter degraded bacteria (i.e., Defluviicoccus and Rhizobacter) and denitrifying functional bacteria (i.e., Dinghuibacter and Amaricoccus) were dominant microorganism when using IPA and conventional carbon sources. Interestingly, the effluent dissolved organic matter (DOM) exhibited a lower susceptibility to transformation into DBP with an IPA carbon source, thus ensuring the safety of reused water. The findings provide valuable insights into utilizing wasted IPA as an effective carbon source in the wastewater treatment process.