Biodegradation of real industrial wastewater containing ethylene glycol by using aerobic granular sludge in a continuous-flow reactor: Performance and resistance mechanism

The application of aerobic granular sludge in continuous-flow treatment of real organic industrial wastewater has been a current research hotspot. This research explored the feasibility of real ethylene glycol wastewater treatment by aerobic granular sludge in a continuous-flow process. In this study, an 80-day continuous-flow reactor operation was established to investigate the toxic effects of ethylene glycol industrial wastewater on aerobic granular sludge and the resistance mechanism of aerobic granules during long-term operation. Results revealed that after 40 days of domestication, the degradation rate of COD for 2000 ± 150 mg/L remained above 85 % and EG concentration was below the detection limit. Flow cytometry results showed that the toxicity of ethylene glycol to cells was mainly reflected in the destruction of cell membranes, leading to the decline of the microbial activity. Long-term exposure to ethylene glycol industrial wastewater would reduce the mechanic strength of aerobic granules. Through metagenomic sequencing technology, it was confirmed that the ability to metabolize organic matter and the defense function were improved by microorganisms in aerobic granules during the process, however, the productivity of cells was reduced, and both the intracellular repair and cytoskeleton synthesis of AGS were inhibited. Based on the KEGG database, a metabolic network of ethylene glycol from granular sludge microorganisms was reconstructed.