Efficient bio-refractory industrial wastewater treatment with mitigated membrane fouling in a membrane bioreactor strengthened by the micro-scale ZVI@GAC galvanic-cells-initiated radical generation and coagulation processes. (1st February 2022)

• Record Type: Journal Article
• Authors: Deng, Shihai; Wang, Qi; Cai, Qinqing; Ong, Say Leong; Hu, Jiangyong
• Is Part Of: Water research. Volume 209(2022)
• Publication Date: 2022-02-01
• Subjects: Membrane bioreactor (MBR) -- Bio-refractory industrial wastewater -- Micro-scale ZVI@GACs -- Iron-carbon galvanic-cells (Fe(0)/C) -- Membrane fouling -- Soluble microbial products; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2021.117943
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Micro-scale ZVI@GAC-based iron-carbon galvanic-cells (ZVI@GACs) was developed. ZVI@GACs initiated OH generation, oxidation, and coagulation processes in MBR. ZVI@GACs improved COD removal of MBR by 14% and mitigated membrane fouling by 71%. Oxidation of SMP was observed in ZVI@GACs-MBR, reducing SMP-polysaccharide by 60%. Coagulation by forming Fe(OH)3 and FeOOH in ZVI@GACs-MBR increased sludge floc size. Abstract: Micro-scale ZVI@GAC-based iron-carbon galvanic-cells (ZVI@GACs) were prepared with the Ca−Si−H/Ca−H formation process and first applied to initiate radical generation and coagulation processes in MBR for treating bio-refractory industrial wastewater (IWW). Batch tests revealed the H2 O2 production (0.19–0.28 mg/L) and OH generation (p-CBA decay, k 1 = 0.040 min −1 ) in ZVI@GACs-dosed system (packing volume of 5%) under aeration. Adoption of ZVI@GACs into aerobic activated sludge process (ZVI@GACs/AS) enhanced TOC degradation ( k 2 ) and phenolic compounds (PHENs) destruction ( k 3 ). ZVI@GACs/AS at ZVI@GACs packing volume of 5%, 10% and 20% improved k 2 from 0.11 h −1 (bare AS) to 0.17, 0.21 and 23 h −1 and k 3 from 0.24 h −1 to 0.36, 0.49 and 0.57 h −1, respectively. The oxygen uptake rate (OUR) and 15-min acute bio-toxicity demonstrated that the bio-toxicity of IWW was reduced and the activity of biomass was enhanced in the ZVI@GACs/AS system. In MBR, ZVI@GACs at packing volume of 10% enhanced COD and PHENs removal by 14% and 22%, respectively. Membrane fouling cycle was prolonged by 71%. The accumulations of EPS-proteins, EPS-polysaccharides, SMP-proteins and SMP-polysaccharides were reduced by 6%, 67%, 27% and 60%, respectively. Fourier transform infrared spectroscopy (FTIR) confirmed the oxidation of SMP-polysaccharides in ZVI@GACs-MBR. The iron ions released from ZVI@GACs showed inhibition on the secretion of SMP-/EPS-proteins. Floc particle size distribution (PSD) and X-ray diffraction (XRD) spectrum confirmed that the coagulation effects of Fe(OH)3 and FeOOH triggered by Fe 3+ increased the sludge floc size and contributed to membrane fouling mitigation. Genus Enterococcus was enriched in MBR with the destruction of PHENs by the ZVI@GACs-initiated radical generation process. The findings of this study confirmed successful development and adoption of ZVI@GACs into MBR for bio-refractory IWW treatment. It also provided an in-depth understanding on the mechanisms of ZVI@GACs-MBR system. Graphical abstract: Image, graphical abstract