Improved anaerobic degradation of purified terephthalic acid wastewater by adding nanoparticles or co-substrates to facilitate the electron transfer process

Abstract

Improving the biodegradation efficiency of terephthalic acid (TA) wastewater processes is highly challenging, particularly in large-scale up-flow anaerobic sludge blanket (UASB) reactors. Importantly, this study proposes to add functional components into UASB reactors to facilitate the electron transfer process to enhance the TA degradation efficiency. The results showed that the complete degradation period of terephthalic acid (TA, 1000 mg L⁻¹) wastewater has been dramatically shortened via adding TiO₂/Fe₃O₄ nanoparticles (NPs, up to 81 days) or ethanol (up to 50 days), in which the significantly improved performance in nanoparticle-added reactors was due to the high accumulation of NPs (Fe₃O₄/TiO₂) functioning as additional ‘bridge-like routes’ for ultrafast electron transfer between the microorganisms, therefore facilitating a ‘pseudo electro-fermentation’ process to strengthen the direct interspecies electron transfer (DIET) process. The addition of ethanol into reactors showed significantly improved performance, but requiring daily addition, while the nanoparticulate materials were only required when the reactor was initially activated. Additionally, comprehensive experiments/perspectives on degrading low-to-high concentration wastewater were also explored in this study, which implied that Fe₃O₄ NPs enabled efficient degradation of high-concentration isophthalic acid (IPA, 18 000 mg L⁻¹) wastewater owing to their high degradation efficiency. Meanwhile TiO₂ NPs were more efficient in dealing with low-concentration TA wastewater due to their cheaper price and high stability in reactors. This study provides essential information for future component-complex, industry-scale wastewater treatment and remediation.