Conversion of polyphenolic polymers in aerobic biochemical treatment

Abstract

Polyphenols are organic substances commonly involved in a wide variety of industrial processes. They are prone to polymerize with other organic chemicals during production and subsequent wastewater treatment section, which yields various persistent and recalcitrant organic chemicals. To better understand the behavior of polyphenolic polymers in wastewater treatment processes and the effect on the biodegradability of wastewater, we explored the conversion of polyphenolic polymers during aerobic biochemical treatment and their relationship with extracellular polymeric substances (EPS). The CODCr (chemical oxygen consumption measured using potassium dichromate) removal efficiency of the polyphenolic polymers with high concentration was only 29.66% with CODCr of 437.5 mg/L, which was far from the wastewater discharge standard (60–100 mg/L, first class standard of GB 8978–1996). In the activated sludge system with stabilized organic matter as the substrate, the effluent had the highest degree of humification with the maximum SUVA value of 6.87 L/(mg∙m). The polyphenolic polymers caused a component variation in EPS, further affecting wastewater's humification degree and degradability. In particular, the content of humic acid-like substances in loose bound EPS (LB-EPS) was up to 4 times more than control, indicating higher aromatization and humification degree and of the waste. On the contrary, the content of polysaccharides in LB-EPS decreased by about 46.2–87.7% in treatments with different concentration of polyphenolic polymer. The high-concentration polyphenol polymers somehow stimulated the microbial production like proteins and humic-like substances. The direct conversion of polyphenol polymers also contributed to the increased humification of wastewater.